vendor: github.com/prometheus/client_golang v1.12.1

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/go.opencensus.io/.gitignore

@@ -0,0 +1,9 @@
+/.idea/
+
+# go.opencensus.io/exporter/aws
+/exporter/aws/
+
+# Exclude vendor, use dep ensure after checkout:
+/vendor/github.com/
+/vendor/golang.org/
+/vendor/google.golang.org/

vendor/go.opencensus.io/.travis.yml

@@ -0,0 +1,17 @@
+language: go
+
+go_import_path: go.opencensus.io
+
+go:
+  - 1.11.x
+
+env:
+  global:
+    GO111MODULE=on
+
+before_script:
+  - make install-tools
+
+script:
+  - make travis-ci
+  - go run internal/check/version.go # TODO move this to makefile

vendor/go.opencensus.io/AUTHORS

@@ -0,0 +1 @@
+Google Inc.

vendor/go.opencensus.io/CONTRIBUTING.md

@@ -0,0 +1,63 @@
+# How to contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Contributor License Agreement
+
+Contributions to this project must be accompanied by a Contributor License
+Agreement. You (or your employer) retain the copyright to your contribution,
+this simply gives us permission to use and redistribute your contributions as
+part of the project. Head over to <https://cla.developers.google.com/> to see
+your current agreements on file or to sign a new one.
+
+You generally only need to submit a CLA once, so if you've already submitted one
+(even if it was for a different project), you probably don't need to do it
+again.
+
+## Code reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult [GitHub Help] for more
+information on using pull requests.
+
+[GitHub Help]: https://help.github.com/articles/about-pull-requests/
+
+## Instructions
+
+Fork the repo, checkout the upstream repo to your GOPATH by:
+
+```
+$ go get -d go.opencensus.io
+```
+
+Add your fork as an origin:
+
+```
+cd $(go env GOPATH)/src/go.opencensus.io
+git remote add fork git@github.com:YOUR_GITHUB_USERNAME/opencensus-go.git
+```
+
+Run tests:
+
+```
+$ make install-tools  # Only first time.
+$ make
+```
+
+Checkout a new branch, make modifications and push the branch to your fork:
+
+```
+$ git checkout -b feature
+# edit files
+$ git commit
+$ git push fork feature
+```
+
+Open a pull request against the main opencensus-go repo.
+
+## General Notes
+This project uses Appveyor and Travis for CI.
+
+The dependencies are managed with `go mod` if you work with the sources under your
+`$GOPATH` you need to set the environment variable `GO111MODULE=on`.

vendor/go.opencensus.io/LICENSE

@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright [yyyy] [name of copyright owner]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

vendor/go.opencensus.io/Makefile

@@ -0,0 +1,97 @@
+# TODO: Fix this on windows.
+ALL_SRC := $(shell find . -name '*.go' \
+								-not -path './vendor/*' \
+								-not -path '*/gen-go/*' \
+								-type f | sort)
+ALL_PKGS := $(shell go list $(sort $(dir $(ALL_SRC))))
+
+GOTEST_OPT?=-v -race -timeout 30s
+GOTEST_OPT_WITH_COVERAGE = $(GOTEST_OPT) -coverprofile=coverage.txt -covermode=atomic
+GOTEST=go test
+GOIMPORTS=goimports
+GOLINT=golint
+GOVET=go vet
+EMBEDMD=embedmd
+# TODO decide if we need to change these names.
+TRACE_ID_LINT_EXCEPTION="type name will be used as trace.TraceID by other packages"
+TRACE_OPTION_LINT_EXCEPTION="type name will be used as trace.TraceOptions by other packages"
+README_FILES := $(shell find . -name '*README.md' | sort | tr '\n' ' ')
+
+.DEFAULT_GOAL := imports-lint-vet-embedmd-test
+
+.PHONY: imports-lint-vet-embedmd-test
+imports-lint-vet-embedmd-test: imports lint vet embedmd test
+
+# TODO enable test-with-coverage in tavis
+.PHONY: travis-ci
+travis-ci: imports lint vet embedmd test test-386
+
+all-pkgs:
+	@echo $(ALL_PKGS) | tr ' ' '\n' | sort
+
+all-srcs:
+	@echo $(ALL_SRC) | tr ' ' '\n' | sort
+
+.PHONY: test
+test:
+	$(GOTEST) $(GOTEST_OPT) $(ALL_PKGS)
+
+.PHONY: test-386
+test-386:
+	GOARCH=386 $(GOTEST) -v -timeout 30s $(ALL_PKGS)
+
+.PHONY: test-with-coverage
+test-with-coverage:
+	$(GOTEST) $(GOTEST_OPT_WITH_COVERAGE) $(ALL_PKGS)
+
+.PHONY: imports
+imports:
+	@IMPORTSOUT=`$(GOIMPORTS) -l $(ALL_SRC) 2>&1`; \
+	if [ "$$IMPORTSOUT" ]; then \
+		echo "$(GOIMPORTS) FAILED => goimports the following files:\n"; \
+		echo "$$IMPORTSOUT\n"; \
+		exit 1; \
+	else \
+	    echo "Imports finished successfully"; \
+	fi
+
+.PHONY: lint
+lint:
+	@LINTOUT=`$(GOLINT) $(ALL_PKGS) | grep -v $(TRACE_ID_LINT_EXCEPTION) | grep -v $(TRACE_OPTION_LINT_EXCEPTION) 2>&1`; \
+	if [ "$$LINTOUT" ]; then \
+		echo "$(GOLINT) FAILED => clean the following lint errors:\n"; \
+		echo "$$LINTOUT\n"; \
+		exit 1; \
+	else \
+	    echo "Lint finished successfully"; \
+	fi
+
+.PHONY: vet
+vet:
+    # TODO: Understand why go vet downloads "github.com/google/go-cmp v0.2.0"
+	@VETOUT=`$(GOVET) ./... | grep -v "go: downloading" 2>&1`; \
+	if [ "$$VETOUT" ]; then \
+		echo "$(GOVET) FAILED => go vet the following files:\n"; \
+		echo "$$VETOUT\n"; \
+		exit 1; \
+	else \
+	    echo "Vet finished successfully"; \
+	fi
+	
+.PHONY: embedmd
+embedmd:
+	@EMBEDMDOUT=`$(EMBEDMD) -d $(README_FILES) 2>&1`; \
+	if [ "$$EMBEDMDOUT" ]; then \
+		echo "$(EMBEDMD) FAILED => embedmd the following files:\n"; \
+		echo "$$EMBEDMDOUT\n"; \
+		exit 1; \
+	else \
+	    echo "Embedmd finished successfully"; \
+	fi
+
+.PHONY: install-tools
+install-tools:
+	go get -u golang.org/x/lint/golint
+	go get -u golang.org/x/tools/cmd/cover
+	go get -u golang.org/x/tools/cmd/goimports
+	go get -u github.com/rakyll/embedmd

vendor/go.opencensus.io/README.md

@@ -0,0 +1,267 @@
+# OpenCensus Libraries for Go
+
+[![Build Status][travis-image]][travis-url]
+[![Windows Build Status][appveyor-image]][appveyor-url]
+[![GoDoc][godoc-image]][godoc-url]
+[![Gitter chat][gitter-image]][gitter-url]
+
+OpenCensus Go is a Go implementation of OpenCensus, a toolkit for
+collecting application performance and behavior monitoring data.
+Currently it consists of three major components: tags, stats and tracing.
+
+#### OpenCensus and OpenTracing have merged to form OpenTelemetry, which serves as the next major version of OpenCensus and OpenTracing. OpenTelemetry will offer backwards compatibility with existing OpenCensus integrations, and we will continue to make security patches to existing OpenCensus libraries for two years. Read more about the merger [here](https://medium.com/opentracing/a-roadmap-to-convergence-b074e5815289).
+
+## Installation
+
+```
+$ go get -u go.opencensus.io
+```
+
+The API of this project is still evolving, see: [Deprecation Policy](#deprecation-policy).
+The use of vendoring or a dependency management tool is recommended.
+
+## Prerequisites
+
+OpenCensus Go libraries require Go 1.8 or later.
+
+## Getting Started
+
+The easiest way to get started using OpenCensus in your application is to use an existing
+integration with your RPC framework:
+
+* [net/http](https://godoc.org/go.opencensus.io/plugin/ochttp)
+* [gRPC](https://godoc.org/go.opencensus.io/plugin/ocgrpc)
+* [database/sql](https://godoc.org/github.com/opencensus-integrations/ocsql)
+* [Go kit](https://godoc.org/github.com/go-kit/kit/tracing/opencensus)
+* [Groupcache](https://godoc.org/github.com/orijtech/groupcache)
+* [Caddy webserver](https://godoc.org/github.com/orijtech/caddy)
+* [MongoDB](https://godoc.org/github.com/orijtech/mongo-go-driver)
+* [Redis gomodule/redigo](https://godoc.org/github.com/orijtech/redigo)
+* [Redis goredis/redis](https://godoc.org/github.com/orijtech/redis)
+* [Memcache](https://godoc.org/github.com/orijtech/gomemcache)
+
+If you're using a framework not listed here, you could either implement your own middleware for your
+framework or use [custom stats](#stats) and [spans](#spans) directly in your application.
+
+## Exporters
+
+OpenCensus can export instrumentation data to various backends.
+OpenCensus has exporter implementations for the following, users
+can implement their own exporters by implementing the exporter interfaces
+([stats](https://godoc.org/go.opencensus.io/stats/view#Exporter),
+[trace](https://godoc.org/go.opencensus.io/trace#Exporter)):
+
+* [Prometheus][exporter-prom] for stats
+* [OpenZipkin][exporter-zipkin] for traces
+* [Stackdriver][exporter-stackdriver] Monitoring for stats and Trace for traces
+* [Jaeger][exporter-jaeger] for traces
+* [AWS X-Ray][exporter-xray] for traces
+* [Datadog][exporter-datadog] for stats and traces
+* [Graphite][exporter-graphite] for stats
+* [Honeycomb][exporter-honeycomb] for traces
+* [New Relic][exporter-newrelic] for stats and traces
+
+## Overview
+
+![OpenCensus Overview](https://i.imgur.com/cf4ElHE.jpg)
+
+In a microservices environment, a user request may go through
+multiple services until there is a response. OpenCensus allows
+you to instrument your services and collect diagnostics data all
+through your services end-to-end.
+
+## Tags
+
+Tags represent propagated key-value pairs. They are propagated using `context.Context`
+in the same process or can be encoded to be transmitted on the wire. Usually, this will
+be handled by an integration plugin, e.g. `ocgrpc.ServerHandler` and `ocgrpc.ClientHandler`
+for gRPC.
+
+Package `tag` allows adding or modifying tags in the current context.
+
+[embedmd]:# (internal/readme/tags.go new)
+```go
+ctx, err := tag.New(ctx,
+	tag.Insert(osKey, "macOS-10.12.5"),
+	tag.Upsert(userIDKey, "cde36753ed"),
+)
+if err != nil {
+	log.Fatal(err)
+}
+```
+
+## Stats
+
+OpenCensus is a low-overhead framework even if instrumentation is always enabled.
+In order to be so, it is optimized to make recording of data points fast
+and separate from the data aggregation.
+
+OpenCensus stats collection happens in two stages:
+
+* Definition of measures and recording of data points
+* Definition of views and aggregation of the recorded data
+
+### Recording
+
+Measurements are data points associated with a measure.
+Recording implicitly tags the set of Measurements with the tags from the
+provided context:
+
+[embedmd]:# (internal/readme/stats.go record)
+```go
+stats.Record(ctx, videoSize.M(102478))
+```
+
+### Views
+
+Views are how Measures are aggregated. You can think of them as queries over the
+set of recorded data points (measurements).
+
+Views have two parts: the tags to group by and the aggregation type used.
+
+Currently three types of aggregations are supported:
+* CountAggregation is used to count the number of times a sample was recorded.
+* DistributionAggregation is used to provide a histogram of the values of the samples.
+* SumAggregation is used to sum up all sample values.
+
+[embedmd]:# (internal/readme/stats.go aggs)
+```go
+distAgg := view.Distribution(1<<32, 2<<32, 3<<32)
+countAgg := view.Count()
+sumAgg := view.Sum()
+```
+
+Here we create a view with the DistributionAggregation over our measure.
+
+[embedmd]:# (internal/readme/stats.go view)
+```go
+if err := view.Register(&view.View{
+	Name:        "example.com/video_size_distribution",
+	Description: "distribution of processed video size over time",
+	Measure:     videoSize,
+	Aggregation: view.Distribution(1<<32, 2<<32, 3<<32),
+}); err != nil {
+	log.Fatalf("Failed to register view: %v", err)
+}
+```
+
+Register begins collecting data for the view. Registered views' data will be
+exported via the registered exporters.
+
+## Traces
+
+A distributed trace tracks the progression of a single user request as
+it is handled by the services and processes that make up an application.
+Each step is called a span in the trace. Spans include metadata about the step,
+including especially the time spent in the step, called the span’s latency.
+
+Below you see a trace and several spans underneath it.
+
+![Traces and spans](https://i.imgur.com/7hZwRVj.png)
+
+### Spans
+
+Span is the unit step in a trace. Each span has a name, latency, status and
+additional metadata.
+
+Below we are starting a span for a cache read and ending it
+when we are done:
+
+[embedmd]:# (internal/readme/trace.go startend)
+```go
+ctx, span := trace.StartSpan(ctx, "cache.Get")
+defer span.End()
+
+// Do work to get from cache.
+```
+
+### Propagation
+
+Spans can have parents or can be root spans if they don't have any parents.
+The current span is propagated in-process and across the network to allow associating
+new child spans with the parent.
+
+In the same process, `context.Context` is used to propagate spans.
+`trace.StartSpan` creates a new span as a root if the current context
+doesn't contain a span. Or, it creates a child of the span that is
+already in current context. The returned context can be used to keep
+propagating the newly created span in the current context.
+
+[embedmd]:# (internal/readme/trace.go startend)
+```go
+ctx, span := trace.StartSpan(ctx, "cache.Get")
+defer span.End()
+
+// Do work to get from cache.
+```
+
+Across the network, OpenCensus provides different propagation
+methods for different protocols.
+
+* gRPC integrations use the OpenCensus' [binary propagation format](https://godoc.org/go.opencensus.io/trace/propagation).
+* HTTP integrations use Zipkin's [B3](https://github.com/openzipkin/b3-propagation)
+  by default but can be configured to use a custom propagation method by setting another
+  [propagation.HTTPFormat](https://godoc.org/go.opencensus.io/trace/propagation#HTTPFormat).
+
+## Execution Tracer
+
+With Go 1.11, OpenCensus Go will support integration with the Go execution tracer.
+See [Debugging Latency in Go](https://medium.com/observability/debugging-latency-in-go-1-11-9f97a7910d68)
+for an example of their mutual use.
+
+## Profiles
+
+OpenCensus tags can be applied as profiler labels
+for users who are on Go 1.9 and above.
+
+[embedmd]:# (internal/readme/tags.go profiler)
+```go
+ctx, err = tag.New(ctx,
+	tag.Insert(osKey, "macOS-10.12.5"),
+	tag.Insert(userIDKey, "fff0989878"),
+)
+if err != nil {
+	log.Fatal(err)
+}
+tag.Do(ctx, func(ctx context.Context) {
+	// Do work.
+	// When profiling is on, samples will be
+	// recorded with the key/values from the tag map.
+})
+```
+
+A screenshot of the CPU profile from the program above:
+
+![CPU profile](https://i.imgur.com/jBKjlkw.png)
+
+## Deprecation Policy
+
+Before version 1.0.0, the following deprecation policy will be observed:
+
+No backwards-incompatible changes will be made except for the removal of symbols that have
+been marked as *Deprecated* for at least one minor release (e.g. 0.9.0 to 0.10.0). A release
+removing the *Deprecated* functionality will be made no sooner than 28 days after the first
+release in which the functionality was marked *Deprecated*.
+
+[travis-image]: https://travis-ci.org/census-instrumentation/opencensus-go.svg?branch=master
+[travis-url]: https://travis-ci.org/census-instrumentation/opencensus-go
+[appveyor-image]: https://ci.appveyor.com/api/projects/status/vgtt29ps1783ig38?svg=true
+[appveyor-url]: https://ci.appveyor.com/project/opencensusgoteam/opencensus-go/branch/master
+[godoc-image]: https://godoc.org/go.opencensus.io?status.svg
+[godoc-url]: https://godoc.org/go.opencensus.io
+[gitter-image]: https://badges.gitter.im/census-instrumentation/lobby.svg
+[gitter-url]: https://gitter.im/census-instrumentation/lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
+
+
+[new-ex]: https://godoc.org/go.opencensus.io/tag#example-NewMap
+[new-replace-ex]: https://godoc.org/go.opencensus.io/tag#example-NewMap--Replace
+
+[exporter-prom]: https://godoc.org/contrib.go.opencensus.io/exporter/prometheus
+[exporter-stackdriver]: https://godoc.org/contrib.go.opencensus.io/exporter/stackdriver
+[exporter-zipkin]: https://godoc.org/contrib.go.opencensus.io/exporter/zipkin
+[exporter-jaeger]: https://godoc.org/contrib.go.opencensus.io/exporter/jaeger
+[exporter-xray]: https://github.com/census-ecosystem/opencensus-go-exporter-aws
+[exporter-datadog]: https://github.com/DataDog/opencensus-go-exporter-datadog
+[exporter-graphite]: https://github.com/census-ecosystem/opencensus-go-exporter-graphite
+[exporter-honeycomb]: https://github.com/honeycombio/opencensus-exporter
+[exporter-newrelic]: https://github.com/newrelic/newrelic-opencensus-exporter-go

vendor/go.opencensus.io/appveyor.yml

@@ -0,0 +1,24 @@
+version: "{build}"
+
+platform: x64
+
+clone_folder: c:\gopath\src\go.opencensus.io
+
+environment:
+  GOPATH: 'c:\gopath'
+  GO111MODULE: 'on'
+  CGO_ENABLED: '0' # See: https://github.com/appveyor/ci/issues/2613
+
+stack: go 1.11
+
+before_test:
+  - go version
+  - go env
+
+build: false
+deploy: false
+
+test_script:
+  - cd %APPVEYOR_BUILD_FOLDER%
+  - go build -v .\...
+  - go test -v .\... # No -race because cgo is disabled

vendor/go.opencensus.io/internal/internal.go

@@ -0,0 +1,37 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal // import "go.opencensus.io/internal"
+
+import (
+	"fmt"
+	"time"
+
+	opencensus "go.opencensus.io"
+)
+
+// UserAgent is the user agent to be added to the outgoing
+// requests from the exporters.
+var UserAgent = fmt.Sprintf("opencensus-go/%s", opencensus.Version())
+
+// MonotonicEndTime returns the end time at present
+// but offset from start, monotonically.
+//
+// The monotonic clock is used in subtractions hence
+// the duration since start added back to start gives
+// end as a monotonic time.
+// See https://golang.org/pkg/time/#hdr-Monotonic_Clocks
+func MonotonicEndTime(start time.Time) time.Time {
+	return start.Add(time.Since(start))
+}

vendor/go.opencensus.io/internal/sanitize.go

@@ -0,0 +1,50 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"strings"
+	"unicode"
+)
+
+const labelKeySizeLimit = 100
+
+// Sanitize returns a string that is trunacated to 100 characters if it's too
+// long, and replaces non-alphanumeric characters to underscores.
+func Sanitize(s string) string {
+	if len(s) == 0 {
+		return s
+	}
+	if len(s) > labelKeySizeLimit {
+		s = s[:labelKeySizeLimit]
+	}
+	s = strings.Map(sanitizeRune, s)
+	if unicode.IsDigit(rune(s[0])) {
+		s = "key_" + s
+	}
+	if s[0] == '_' {
+		s = "key" + s
+	}
+	return s
+}
+
+// converts anything that is not a letter or digit to an underscore
+func sanitizeRune(r rune) rune {
+	if unicode.IsLetter(r) || unicode.IsDigit(r) {
+		return r
+	}
+	// Everything else turns into an underscore
+	return '_'
+}

vendor/go.opencensus.io/internal/tagencoding/tagencoding.go

@@ -0,0 +1,75 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// Package tagencoding contains the tag encoding
+// used interally by the stats collector.
+package tagencoding // import "go.opencensus.io/internal/tagencoding"
+
+// Values represent the encoded buffer for the values.
+type Values struct {
+	Buffer     []byte
+	WriteIndex int
+	ReadIndex  int
+}
+
+func (vb *Values) growIfRequired(expected int) {
+	if len(vb.Buffer)-vb.WriteIndex < expected {
+		tmp := make([]byte, 2*(len(vb.Buffer)+1)+expected)
+		copy(tmp, vb.Buffer)
+		vb.Buffer = tmp
+	}
+}
+
+// WriteValue is the helper method to encode Values from map[Key][]byte.
+func (vb *Values) WriteValue(v []byte) {
+	length := len(v) & 0xff
+	vb.growIfRequired(1 + length)
+
+	// writing length of v
+	vb.Buffer[vb.WriteIndex] = byte(length)
+	vb.WriteIndex++
+
+	if length == 0 {
+		// No value was encoded for this key
+		return
+	}
+
+	// writing v
+	copy(vb.Buffer[vb.WriteIndex:], v[:length])
+	vb.WriteIndex += length
+}
+
+// ReadValue is the helper method to decode Values to a map[Key][]byte.
+func (vb *Values) ReadValue() []byte {
+	// read length of v
+	length := int(vb.Buffer[vb.ReadIndex])
+	vb.ReadIndex++
+	if length == 0 {
+		// No value was encoded for this key
+		return nil
+	}
+
+	// read value of v
+	v := make([]byte, length)
+	endIdx := vb.ReadIndex + length
+	copy(v, vb.Buffer[vb.ReadIndex:endIdx])
+	vb.ReadIndex = endIdx
+	return v
+}
+
+// Bytes returns a reference to already written bytes in the Buffer.
+func (vb *Values) Bytes() []byte {
+	return vb.Buffer[:vb.WriteIndex]
+}

vendor/go.opencensus.io/internal/traceinternals.go

@@ -0,0 +1,53 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"time"
+)
+
+// Trace allows internal access to some trace functionality.
+// TODO(#412): remove this
+var Trace interface{}
+
+// LocalSpanStoreEnabled true if the local span store is enabled.
+var LocalSpanStoreEnabled bool
+
+// BucketConfiguration stores the number of samples to store for span buckets
+// for successful and failed spans for a particular span name.
+type BucketConfiguration struct {
+	Name                 string
+	MaxRequestsSucceeded int
+	MaxRequestsErrors    int
+}
+
+// PerMethodSummary is a summary of the spans stored for a single span name.
+type PerMethodSummary struct {
+	Active         int
+	LatencyBuckets []LatencyBucketSummary
+	ErrorBuckets   []ErrorBucketSummary
+}
+
+// LatencyBucketSummary is a summary of a latency bucket.
+type LatencyBucketSummary struct {
+	MinLatency, MaxLatency time.Duration
+	Size                   int
+}
+
+// ErrorBucketSummary is a summary of an error bucket.
+type ErrorBucketSummary struct {
+	ErrorCode int32
+	Size      int
+}

vendor/go.opencensus.io/metric/metricdata/doc.go

@@ -0,0 +1,19 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package metricdata contains the metrics data model.
+//
+// This is an EXPERIMENTAL package, and may change in arbitrary ways without
+// notice.
+package metricdata // import "go.opencensus.io/metric/metricdata"

vendor/go.opencensus.io/metric/metricdata/exemplar.go

@@ -0,0 +1,38 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricdata
+
+import (
+	"time"
+)
+
+// Exemplars keys.
+const (
+	AttachmentKeySpanContext = "SpanContext"
+)
+
+// Exemplar is an example data point associated with each bucket of a
+// distribution type aggregation.
+//
+// Their purpose is to provide an example of the kind of thing
+// (request, RPC, trace span, etc.) that resulted in that measurement.
+type Exemplar struct {
+	Value       float64     // the value that was recorded
+	Timestamp   time.Time   // the time the value was recorded
+	Attachments Attachments // attachments (if any)
+}
+
+// Attachments is a map of extra values associated with a recorded data point.
+type Attachments map[string]interface{}

vendor/go.opencensus.io/metric/metricdata/label.go

@@ -0,0 +1,35 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricdata
+
+// LabelKey represents key of a label. It has optional
+// description attribute.
+type LabelKey struct {
+	Key         string
+	Description string
+}
+
+// LabelValue represents the value of a label.
+// The zero value represents a missing label value, which may be treated
+// differently to an empty string value by some back ends.
+type LabelValue struct {
+	Value   string // string value of the label
+	Present bool   // flag that indicated whether a value is present or not
+}
+
+// NewLabelValue creates a new non-nil LabelValue that represents the given string.
+func NewLabelValue(val string) LabelValue {
+	return LabelValue{Value: val, Present: true}
+}

vendor/go.opencensus.io/metric/metricdata/metric.go

@@ -0,0 +1,46 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricdata
+
+import (
+	"time"
+
+	"go.opencensus.io/resource"
+)
+
+// Descriptor holds metadata about a metric.
+type Descriptor struct {
+	Name        string     // full name of the metric
+	Description string     // human-readable description
+	Unit        Unit       // units for the measure
+	Type        Type       // type of measure
+	LabelKeys   []LabelKey // label keys
+}
+
+// Metric represents a quantity measured against a resource with different
+// label value combinations.
+type Metric struct {
+	Descriptor Descriptor         // metric descriptor
+	Resource   *resource.Resource // resource against which this was measured
+	TimeSeries []*TimeSeries      // one time series for each combination of label values
+}
+
+// TimeSeries is a sequence of points associated with a combination of label
+// values.
+type TimeSeries struct {
+	LabelValues []LabelValue // label values, same order as keys in the metric descriptor
+	Points      []Point      // points sequence
+	StartTime   time.Time    // time we started recording this time series
+}

vendor/go.opencensus.io/metric/metricdata/point.go

@@ -0,0 +1,193 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricdata
+
+import (
+	"time"
+)
+
+// Point is a single data point of a time series.
+type Point struct {
+	// Time is the point in time that this point represents in a time series.
+	Time time.Time
+	// Value is the value of this point. Prefer using ReadValue to switching on
+	// the value type, since new value types might be added.
+	Value interface{}
+}
+
+//go:generate stringer -type ValueType
+
+// NewFloat64Point creates a new Point holding a float64 value.
+func NewFloat64Point(t time.Time, val float64) Point {
+	return Point{
+		Value: val,
+		Time:  t,
+	}
+}
+
+// NewInt64Point creates a new Point holding an int64 value.
+func NewInt64Point(t time.Time, val int64) Point {
+	return Point{
+		Value: val,
+		Time:  t,
+	}
+}
+
+// NewDistributionPoint creates a new Point holding a Distribution value.
+func NewDistributionPoint(t time.Time, val *Distribution) Point {
+	return Point{
+		Value: val,
+		Time:  t,
+	}
+}
+
+// NewSummaryPoint creates a new Point holding a Summary value.
+func NewSummaryPoint(t time.Time, val *Summary) Point {
+	return Point{
+		Value: val,
+		Time:  t,
+	}
+}
+
+// ValueVisitor allows reading the value of a point.
+type ValueVisitor interface {
+	VisitFloat64Value(float64)
+	VisitInt64Value(int64)
+	VisitDistributionValue(*Distribution)
+	VisitSummaryValue(*Summary)
+}
+
+// ReadValue accepts a ValueVisitor and calls the appropriate method with the
+// value of this point.
+// Consumers of Point should use this in preference to switching on the type
+// of the value directly, since new value types may be added.
+func (p Point) ReadValue(vv ValueVisitor) {
+	switch v := p.Value.(type) {
+	case int64:
+		vv.VisitInt64Value(v)
+	case float64:
+		vv.VisitFloat64Value(v)
+	case *Distribution:
+		vv.VisitDistributionValue(v)
+	case *Summary:
+		vv.VisitSummaryValue(v)
+	default:
+		panic("unexpected value type")
+	}
+}
+
+// Distribution contains summary statistics for a population of values. It
+// optionally contains a histogram representing the distribution of those
+// values across a set of buckets.
+type Distribution struct {
+	// Count is the number of values in the population. Must be non-negative. This value
+	// must equal the sum of the values in bucket_counts if a histogram is
+	// provided.
+	Count int64
+	// Sum is the sum of the values in the population. If count is zero then this field
+	// must be zero.
+	Sum float64
+	// SumOfSquaredDeviation is the sum of squared deviations from the mean of the values in the
+	// population. For values x_i this is:
+	//
+	//     Sum[i=1..n]((x_i - mean)^2)
+	//
+	// Knuth, "The Art of Computer Programming", Vol. 2, page 323, 3rd edition
+	// describes Welford's method for accumulating this sum in one pass.
+	//
+	// If count is zero then this field must be zero.
+	SumOfSquaredDeviation float64
+	// BucketOptions describes the bounds of the histogram buckets in this
+	// distribution.
+	//
+	// A Distribution may optionally contain a histogram of the values in the
+	// population.
+	//
+	// If nil, there is no associated histogram.
+	BucketOptions *BucketOptions
+	// Bucket If the distribution does not have a histogram, then omit this field.
+	// If there is a histogram, then the sum of the values in the Bucket counts
+	// must equal the value in the count field of the distribution.
+	Buckets []Bucket
+}
+
+// BucketOptions describes the bounds of the histogram buckets in this
+// distribution.
+type BucketOptions struct {
+	// Bounds specifies a set of bucket upper bounds.
+	// This defines len(bounds) + 1 (= N) buckets. The boundaries for bucket
+	// index i are:
+	//
+	// [0, Bounds[i]) for i == 0
+	// [Bounds[i-1], Bounds[i]) for 0 < i < N-1
+	// [Bounds[i-1], +infinity) for i == N-1
+	Bounds []float64
+}
+
+// Bucket represents a single bucket (value range) in a distribution.
+type Bucket struct {
+	// Count is the number of values in each bucket of the histogram, as described in
+	// bucket_bounds.
+	Count int64
+	// Exemplar associated with this bucket (if any).
+	Exemplar *Exemplar
+}
+
+// Summary is a representation of percentiles.
+type Summary struct {
+	// Count is the cumulative count (if available).
+	Count int64
+	// Sum is the cumulative sum of values  (if available).
+	Sum float64
+	// HasCountAndSum is true if Count and Sum are available.
+	HasCountAndSum bool
+	// Snapshot represents percentiles calculated over an arbitrary time window.
+	// The values in this struct can be reset at arbitrary unknown times, with
+	// the requirement that all of them are reset at the same time.
+	Snapshot Snapshot
+}
+
+// Snapshot represents percentiles over an arbitrary time.
+// The values in this struct can be reset at arbitrary unknown times, with
+// the requirement that all of them are reset at the same time.
+type Snapshot struct {
+	// Count is the number of values in the snapshot. Optional since some systems don't
+	// expose this. Set to 0 if not available.
+	Count int64
+	// Sum is the sum of values in the snapshot. Optional since some systems don't
+	// expose this. If count is 0 then this field must be zero.
+	Sum float64
+	// Percentiles is a map from percentile (range (0-100.0]) to the value of
+	// the percentile.
+	Percentiles map[float64]float64
+}
+
+//go:generate stringer -type Type
+
+// Type is the overall type of metric, including its value type and whether it
+// represents a cumulative total (since the start time) or if it represents a
+// gauge value.
+type Type int
+
+// Metric types.
+const (
+	TypeGaugeInt64 Type = iota
+	TypeGaugeFloat64
+	TypeGaugeDistribution
+	TypeCumulativeInt64
+	TypeCumulativeFloat64
+	TypeCumulativeDistribution
+	TypeSummary
+)

vendor/go.opencensus.io/metric/metricdata/type_string.go

@@ -0,0 +1,16 @@
+// Code generated by "stringer -type Type"; DO NOT EDIT.
+
+package metricdata
+
+import "strconv"
+
+const _Type_name = "TypeGaugeInt64TypeGaugeFloat64TypeGaugeDistributionTypeCumulativeInt64TypeCumulativeFloat64TypeCumulativeDistributionTypeSummary"
+
+var _Type_index = [...]uint8{0, 14, 30, 51, 70, 91, 117, 128}
+
+func (i Type) String() string {
+	if i < 0 || i >= Type(len(_Type_index)-1) {
+		return "Type(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Type_name[_Type_index[i]:_Type_index[i+1]]
+}

vendor/go.opencensus.io/metric/metricdata/unit.go

@@ -0,0 +1,27 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricdata
+
+// Unit is a string encoded according to the case-sensitive abbreviations from the
+// Unified Code for Units of Measure: http://unitsofmeasure.org/ucum.html
+type Unit string
+
+// Predefined units. To record against a unit not represented here, create your
+// own Unit type constant from a string.
+const (
+	UnitDimensionless Unit = "1"
+	UnitBytes         Unit = "By"
+	UnitMilliseconds  Unit = "ms"
+)

vendor/go.opencensus.io/metric/metricproducer/manager.go

@@ -0,0 +1,78 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricproducer
+
+import (
+	"sync"
+)
+
+// Manager maintains a list of active producers. Producers can register
+// with the manager to allow readers to read all metrics provided by them.
+// Readers can retrieve all producers registered with the manager,
+// read metrics from the producers and export them.
+type Manager struct {
+	mu        sync.RWMutex
+	producers map[Producer]struct{}
+}
+
+var prodMgr *Manager
+var once sync.Once
+
+// GlobalManager is a single instance of producer manager
+// that is used by all producers and all readers.
+func GlobalManager() *Manager {
+	once.Do(func() {
+		prodMgr = &Manager{}
+		prodMgr.producers = make(map[Producer]struct{})
+	})
+	return prodMgr
+}
+
+// AddProducer adds the producer to the Manager if it is not already present.
+func (pm *Manager) AddProducer(producer Producer) {
+	if producer == nil {
+		return
+	}
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	pm.producers[producer] = struct{}{}
+}
+
+// DeleteProducer deletes the producer from the Manager if it is present.
+func (pm *Manager) DeleteProducer(producer Producer) {
+	if producer == nil {
+		return
+	}
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	delete(pm.producers, producer)
+}
+
+// GetAll returns a slice of all producer currently registered with
+// the Manager. For each call it generates a new slice. The slice
+// should not be cached as registration may change at any time. It is
+// typically called periodically by exporter to read metrics from
+// the producers.
+func (pm *Manager) GetAll() []Producer {
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	producers := make([]Producer, len(pm.producers))
+	i := 0
+	for producer := range pm.producers {
+		producers[i] = producer
+		i++
+	}
+	return producers
+}

vendor/go.opencensus.io/metric/metricproducer/producer.go

@@ -0,0 +1,28 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metricproducer
+
+import (
+	"go.opencensus.io/metric/metricdata"
+)
+
+// Producer is a source of metrics.
+type Producer interface {
+	// Read should return the current values of all metrics supported by this
+	// metric provider.
+	// The returned metrics should be unique for each combination of name and
+	// resource.
+	Read() []*metricdata.Metric
+}

vendor/go.opencensus.io/opencensus.go

@@ -0,0 +1,21 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package opencensus contains Go support for OpenCensus.
+package opencensus // import "go.opencensus.io"
+
+// Version is the current release version of OpenCensus in use.
+func Version() string {
+	return "0.23.0"
+}

vendor/go.opencensus.io/plugin/ochttp/client.go

@@ -0,0 +1,117 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"net/http"
+	"net/http/httptrace"
+
+	"go.opencensus.io/trace"
+	"go.opencensus.io/trace/propagation"
+)
+
+// Transport is an http.RoundTripper that instruments all outgoing requests with
+// OpenCensus stats and tracing.
+//
+// The zero value is intended to be a useful default, but for
+// now it's recommended that you explicitly set Propagation, since the default
+// for this may change.
+type Transport struct {
+	// Base may be set to wrap another http.RoundTripper that does the actual
+	// requests. By default http.DefaultTransport is used.
+	//
+	// If base HTTP roundtripper implements CancelRequest,
+	// the returned round tripper will be cancelable.
+	Base http.RoundTripper
+
+	// Propagation defines how traces are propagated. If unspecified, a default
+	// (currently B3 format) will be used.
+	Propagation propagation.HTTPFormat
+
+	// StartOptions are applied to the span started by this Transport around each
+	// request.
+	//
+	// StartOptions.SpanKind will always be set to trace.SpanKindClient
+	// for spans started by this transport.
+	StartOptions trace.StartOptions
+
+	// GetStartOptions allows to set start options per request. If set,
+	// StartOptions is going to be ignored.
+	GetStartOptions func(*http.Request) trace.StartOptions
+
+	// NameFromRequest holds the function to use for generating the span name
+	// from the information found in the outgoing HTTP Request. By default the
+	// name equals the URL Path.
+	FormatSpanName func(*http.Request) string
+
+	// NewClientTrace may be set to a function allowing the current *trace.Span
+	// to be annotated with HTTP request event information emitted by the
+	// httptrace package.
+	NewClientTrace func(*http.Request, *trace.Span) *httptrace.ClientTrace
+
+	// TODO: Implement tag propagation for HTTP.
+}
+
+// RoundTrip implements http.RoundTripper, delegating to Base and recording stats and traces for the request.
+func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	rt := t.base()
+	if isHealthEndpoint(req.URL.Path) {
+		return rt.RoundTrip(req)
+	}
+	// TODO: remove excessive nesting of http.RoundTrippers here.
+	format := t.Propagation
+	if format == nil {
+		format = defaultFormat
+	}
+	spanNameFormatter := t.FormatSpanName
+	if spanNameFormatter == nil {
+		spanNameFormatter = spanNameFromURL
+	}
+
+	startOpts := t.StartOptions
+	if t.GetStartOptions != nil {
+		startOpts = t.GetStartOptions(req)
+	}
+
+	rt = &traceTransport{
+		base:   rt,
+		format: format,
+		startOptions: trace.StartOptions{
+			Sampler:  startOpts.Sampler,
+			SpanKind: trace.SpanKindClient,
+		},
+		formatSpanName: spanNameFormatter,
+		newClientTrace: t.NewClientTrace,
+	}
+	rt = statsTransport{base: rt}
+	return rt.RoundTrip(req)
+}
+
+func (t *Transport) base() http.RoundTripper {
+	if t.Base != nil {
+		return t.Base
+	}
+	return http.DefaultTransport
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t *Transport) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := t.base().(canceler); ok {
+		cr.CancelRequest(req)
+	}
+}

vendor/go.opencensus.io/plugin/ochttp/client_stats.go

@@ -0,0 +1,143 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"go.opencensus.io/stats"
+	"go.opencensus.io/tag"
+)
+
+// statsTransport is an http.RoundTripper that collects stats for the outgoing requests.
+type statsTransport struct {
+	base http.RoundTripper
+}
+
+// RoundTrip implements http.RoundTripper, delegating to Base and recording stats for the request.
+func (t statsTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	ctx, _ := tag.New(req.Context(),
+		tag.Upsert(KeyClientHost, req.Host),
+		tag.Upsert(Host, req.Host),
+		tag.Upsert(KeyClientPath, req.URL.Path),
+		tag.Upsert(Path, req.URL.Path),
+		tag.Upsert(KeyClientMethod, req.Method),
+		tag.Upsert(Method, req.Method))
+	req = req.WithContext(ctx)
+	track := &tracker{
+		start: time.Now(),
+		ctx:   ctx,
+	}
+	if req.Body == nil {
+		// TODO: Handle cases where ContentLength is not set.
+		track.reqSize = -1
+	} else if req.ContentLength > 0 {
+		track.reqSize = req.ContentLength
+	}
+	stats.Record(ctx, ClientRequestCount.M(1))
+
+	// Perform request.
+	resp, err := t.base.RoundTrip(req)
+
+	if err != nil {
+		track.statusCode = http.StatusInternalServerError
+		track.end()
+	} else {
+		track.statusCode = resp.StatusCode
+		if req.Method != "HEAD" {
+			track.respContentLength = resp.ContentLength
+		}
+		if resp.Body == nil {
+			track.end()
+		} else {
+			track.body = resp.Body
+			resp.Body = wrappedBody(track, resp.Body)
+		}
+	}
+	return resp, err
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t statsTransport) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := t.base.(canceler); ok {
+		cr.CancelRequest(req)
+	}
+}
+
+type tracker struct {
+	ctx               context.Context
+	respSize          int64
+	respContentLength int64
+	reqSize           int64
+	start             time.Time
+	body              io.ReadCloser
+	statusCode        int
+	endOnce           sync.Once
+}
+
+var _ io.ReadCloser = (*tracker)(nil)
+
+func (t *tracker) end() {
+	t.endOnce.Do(func() {
+		latencyMs := float64(time.Since(t.start)) / float64(time.Millisecond)
+		respSize := t.respSize
+		if t.respSize == 0 && t.respContentLength > 0 {
+			respSize = t.respContentLength
+		}
+		m := []stats.Measurement{
+			ClientSentBytes.M(t.reqSize),
+			ClientReceivedBytes.M(respSize),
+			ClientRoundtripLatency.M(latencyMs),
+			ClientLatency.M(latencyMs),
+			ClientResponseBytes.M(t.respSize),
+		}
+		if t.reqSize >= 0 {
+			m = append(m, ClientRequestBytes.M(t.reqSize))
+		}
+
+		stats.RecordWithTags(t.ctx, []tag.Mutator{
+			tag.Upsert(StatusCode, strconv.Itoa(t.statusCode)),
+			tag.Upsert(KeyClientStatus, strconv.Itoa(t.statusCode)),
+		}, m...)
+	})
+}
+
+func (t *tracker) Read(b []byte) (int, error) {
+	n, err := t.body.Read(b)
+	t.respSize += int64(n)
+	switch err {
+	case nil:
+		return n, nil
+	case io.EOF:
+		t.end()
+	}
+	return n, err
+}
+
+func (t *tracker) Close() error {
+	// Invoking endSpan on Close will help catch the cases
+	// in which a read returned a non-nil error, we set the
+	// span status but didn't end the span.
+	t.end()
+	return t.body.Close()
+}

vendor/go.opencensus.io/plugin/ochttp/doc.go

@@ -0,0 +1,19 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package ochttp provides OpenCensus instrumentation for net/http package.
+//
+// For server instrumentation, see Handler. For client-side instrumentation,
+// see Transport.
+package ochttp // import "go.opencensus.io/plugin/ochttp"

vendor/go.opencensus.io/plugin/ochttp/propagation/b3/b3.go

@@ -0,0 +1,123 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package b3 contains a propagation.HTTPFormat implementation
+// for B3 propagation. See https://github.com/openzipkin/b3-propagation
+// for more details.
+package b3 // import "go.opencensus.io/plugin/ochttp/propagation/b3"
+
+import (
+	"encoding/hex"
+	"net/http"
+
+	"go.opencensus.io/trace"
+	"go.opencensus.io/trace/propagation"
+)
+
+// B3 headers that OpenCensus understands.
+const (
+	TraceIDHeader = "X-B3-TraceId"
+	SpanIDHeader  = "X-B3-SpanId"
+	SampledHeader = "X-B3-Sampled"
+)
+
+// HTTPFormat implements propagation.HTTPFormat to propagate
+// traces in HTTP headers in B3 propagation format.
+// HTTPFormat skips the X-B3-ParentId and X-B3-Flags headers
+// because there are additional fields not represented in the
+// OpenCensus span context. Spans created from the incoming
+// header will be the direct children of the client-side span.
+// Similarly, receiver of the outgoing spans should use client-side
+// span created by OpenCensus as the parent.
+type HTTPFormat struct{}
+
+var _ propagation.HTTPFormat = (*HTTPFormat)(nil)
+
+// SpanContextFromRequest extracts a B3 span context from incoming requests.
+func (f *HTTPFormat) SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool) {
+	tid, ok := ParseTraceID(req.Header.Get(TraceIDHeader))
+	if !ok {
+		return trace.SpanContext{}, false
+	}
+	sid, ok := ParseSpanID(req.Header.Get(SpanIDHeader))
+	if !ok {
+		return trace.SpanContext{}, false
+	}
+	sampled, _ := ParseSampled(req.Header.Get(SampledHeader))
+	return trace.SpanContext{
+		TraceID:      tid,
+		SpanID:       sid,
+		TraceOptions: sampled,
+	}, true
+}
+
+// ParseTraceID parses the value of the X-B3-TraceId header.
+func ParseTraceID(tid string) (trace.TraceID, bool) {
+	if tid == "" {
+		return trace.TraceID{}, false
+	}
+	b, err := hex.DecodeString(tid)
+	if err != nil || len(b) > 16 {
+		return trace.TraceID{}, false
+	}
+	var traceID trace.TraceID
+	if len(b) <= 8 {
+		// The lower 64-bits.
+		start := 8 + (8 - len(b))
+		copy(traceID[start:], b)
+	} else {
+		start := 16 - len(b)
+		copy(traceID[start:], b)
+	}
+
+	return traceID, true
+}
+
+// ParseSpanID parses the value of the X-B3-SpanId or X-B3-ParentSpanId headers.
+func ParseSpanID(sid string) (spanID trace.SpanID, ok bool) {
+	if sid == "" {
+		return trace.SpanID{}, false
+	}
+	b, err := hex.DecodeString(sid)
+	if err != nil || len(b) > 8 {
+		return trace.SpanID{}, false
+	}
+	start := 8 - len(b)
+	copy(spanID[start:], b)
+	return spanID, true
+}
+
+// ParseSampled parses the value of the X-B3-Sampled header.
+func ParseSampled(sampled string) (trace.TraceOptions, bool) {
+	switch sampled {
+	case "true", "1":
+		return trace.TraceOptions(1), true
+	default:
+		return trace.TraceOptions(0), false
+	}
+}
+
+// SpanContextToRequest modifies the given request to include B3 headers.
+func (f *HTTPFormat) SpanContextToRequest(sc trace.SpanContext, req *http.Request) {
+	req.Header.Set(TraceIDHeader, hex.EncodeToString(sc.TraceID[:]))
+	req.Header.Set(SpanIDHeader, hex.EncodeToString(sc.SpanID[:]))
+
+	var sampled string
+	if sc.IsSampled() {
+		sampled = "1"
+	} else {
+		sampled = "0"
+	}
+	req.Header.Set(SampledHeader, sampled)
+}

vendor/go.opencensus.io/plugin/ochttp/route.go

@@ -0,0 +1,61 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"context"
+	"net/http"
+
+	"go.opencensus.io/tag"
+)
+
+// SetRoute sets the http_server_route tag to the given value.
+// It's useful when an HTTP framework does not support the http.Handler interface
+// and using WithRouteTag is not an option, but provides a way to hook into the request flow.
+func SetRoute(ctx context.Context, route string) {
+	if a, ok := ctx.Value(addedTagsKey{}).(*addedTags); ok {
+		a.t = append(a.t, tag.Upsert(KeyServerRoute, route))
+	}
+}
+
+// WithRouteTag returns an http.Handler that records stats with the
+// http_server_route tag set to the given value.
+func WithRouteTag(handler http.Handler, route string) http.Handler {
+	return taggedHandlerFunc(func(w http.ResponseWriter, r *http.Request) []tag.Mutator {
+		addRoute := []tag.Mutator{tag.Upsert(KeyServerRoute, route)}
+		ctx, _ := tag.New(r.Context(), addRoute...)
+		r = r.WithContext(ctx)
+		handler.ServeHTTP(w, r)
+		return addRoute
+	})
+}
+
+// taggedHandlerFunc is a http.Handler that returns tags describing the
+// processing of the request. These tags will be recorded along with the
+// measures in this package at the end of the request.
+type taggedHandlerFunc func(w http.ResponseWriter, r *http.Request) []tag.Mutator
+
+func (h taggedHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	tags := h(w, r)
+	if a, ok := r.Context().Value(addedTagsKey{}).(*addedTags); ok {
+		a.t = append(a.t, tags...)
+	}
+}
+
+type addedTagsKey struct{}
+
+type addedTags struct {
+	t []tag.Mutator
+}

vendor/go.opencensus.io/plugin/ochttp/server.go

@@ -0,0 +1,453 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strconv"
+	"sync"
+	"time"
+
+	"go.opencensus.io/stats"
+	"go.opencensus.io/tag"
+	"go.opencensus.io/trace"
+	"go.opencensus.io/trace/propagation"
+)
+
+// Handler is an http.Handler wrapper to instrument your HTTP server with
+// OpenCensus. It supports both stats and tracing.
+//
+// Tracing
+//
+// This handler is aware of the incoming request's span, reading it from request
+// headers as configured using the Propagation field.
+// The extracted span can be accessed from the incoming request's
+// context.
+//
+//    span := trace.FromContext(r.Context())
+//
+// The server span will be automatically ended at the end of ServeHTTP.
+type Handler struct {
+	// Propagation defines how traces are propagated. If unspecified,
+	// B3 propagation will be used.
+	Propagation propagation.HTTPFormat
+
+	// Handler is the handler used to handle the incoming request.
+	Handler http.Handler
+
+	// StartOptions are applied to the span started by this Handler around each
+	// request.
+	//
+	// StartOptions.SpanKind will always be set to trace.SpanKindServer
+	// for spans started by this transport.
+	StartOptions trace.StartOptions
+
+	// GetStartOptions allows to set start options per request. If set,
+	// StartOptions is going to be ignored.
+	GetStartOptions func(*http.Request) trace.StartOptions
+
+	// IsPublicEndpoint should be set to true for publicly accessible HTTP(S)
+	// servers. If true, any trace metadata set on the incoming request will
+	// be added as a linked trace instead of being added as a parent of the
+	// current trace.
+	IsPublicEndpoint bool
+
+	// FormatSpanName holds the function to use for generating the span name
+	// from the information found in the incoming HTTP Request. By default the
+	// name equals the URL Path.
+	FormatSpanName func(*http.Request) string
+
+	// IsHealthEndpoint holds the function to use for determining if the
+	// incoming HTTP request should be considered a health check. This is in
+	// addition to the private isHealthEndpoint func which may also indicate
+	// tracing should be skipped.
+	IsHealthEndpoint func(*http.Request) bool
+}
+
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	var tags addedTags
+	r, traceEnd := h.startTrace(w, r)
+	defer traceEnd()
+	w, statsEnd := h.startStats(w, r)
+	defer statsEnd(&tags)
+	handler := h.Handler
+	if handler == nil {
+		handler = http.DefaultServeMux
+	}
+	r = r.WithContext(context.WithValue(r.Context(), addedTagsKey{}, &tags))
+	handler.ServeHTTP(w, r)
+}
+
+func (h *Handler) startTrace(w http.ResponseWriter, r *http.Request) (*http.Request, func()) {
+	if h.IsHealthEndpoint != nil && h.IsHealthEndpoint(r) || isHealthEndpoint(r.URL.Path) {
+		return r, func() {}
+	}
+	var name string
+	if h.FormatSpanName == nil {
+		name = spanNameFromURL(r)
+	} else {
+		name = h.FormatSpanName(r)
+	}
+	ctx := r.Context()
+
+	startOpts := h.StartOptions
+	if h.GetStartOptions != nil {
+		startOpts = h.GetStartOptions(r)
+	}
+
+	var span *trace.Span
+	sc, ok := h.extractSpanContext(r)
+	if ok && !h.IsPublicEndpoint {
+		ctx, span = trace.StartSpanWithRemoteParent(ctx, name, sc,
+			trace.WithSampler(startOpts.Sampler),
+			trace.WithSpanKind(trace.SpanKindServer))
+	} else {
+		ctx, span = trace.StartSpan(ctx, name,
+			trace.WithSampler(startOpts.Sampler),
+			trace.WithSpanKind(trace.SpanKindServer),
+		)
+		if ok {
+			span.AddLink(trace.Link{
+				TraceID:    sc.TraceID,
+				SpanID:     sc.SpanID,
+				Type:       trace.LinkTypeParent,
+				Attributes: nil,
+			})
+		}
+	}
+	span.AddAttributes(requestAttrs(r)...)
+	if r.Body == nil {
+		// TODO: Handle cases where ContentLength is not set.
+	} else if r.ContentLength > 0 {
+		span.AddMessageReceiveEvent(0, /* TODO: messageID */
+			r.ContentLength, -1)
+	}
+	return r.WithContext(ctx), span.End
+}
+
+func (h *Handler) extractSpanContext(r *http.Request) (trace.SpanContext, bool) {
+	if h.Propagation == nil {
+		return defaultFormat.SpanContextFromRequest(r)
+	}
+	return h.Propagation.SpanContextFromRequest(r)
+}
+
+func (h *Handler) startStats(w http.ResponseWriter, r *http.Request) (http.ResponseWriter, func(tags *addedTags)) {
+	ctx, _ := tag.New(r.Context(),
+		tag.Upsert(Host, r.Host),
+		tag.Upsert(Path, r.URL.Path),
+		tag.Upsert(Method, r.Method))
+	track := &trackingResponseWriter{
+		start:  time.Now(),
+		ctx:    ctx,
+		writer: w,
+	}
+	if r.Body == nil {
+		// TODO: Handle cases where ContentLength is not set.
+		track.reqSize = -1
+	} else if r.ContentLength > 0 {
+		track.reqSize = r.ContentLength
+	}
+	stats.Record(ctx, ServerRequestCount.M(1))
+	return track.wrappedResponseWriter(), track.end
+}
+
+type trackingResponseWriter struct {
+	ctx        context.Context
+	reqSize    int64
+	respSize   int64
+	start      time.Time
+	statusCode int
+	statusLine string
+	endOnce    sync.Once
+	writer     http.ResponseWriter
+}
+
+// Compile time assertion for ResponseWriter interface
+var _ http.ResponseWriter = (*trackingResponseWriter)(nil)
+
+func (t *trackingResponseWriter) end(tags *addedTags) {
+	t.endOnce.Do(func() {
+		if t.statusCode == 0 {
+			t.statusCode = 200
+		}
+
+		span := trace.FromContext(t.ctx)
+		span.SetStatus(TraceStatus(t.statusCode, t.statusLine))
+		span.AddAttributes(trace.Int64Attribute(StatusCodeAttribute, int64(t.statusCode)))
+
+		m := []stats.Measurement{
+			ServerLatency.M(float64(time.Since(t.start)) / float64(time.Millisecond)),
+			ServerResponseBytes.M(t.respSize),
+		}
+		if t.reqSize >= 0 {
+			m = append(m, ServerRequestBytes.M(t.reqSize))
+		}
+		allTags := make([]tag.Mutator, len(tags.t)+1)
+		allTags[0] = tag.Upsert(StatusCode, strconv.Itoa(t.statusCode))
+		copy(allTags[1:], tags.t)
+		stats.RecordWithTags(t.ctx, allTags, m...)
+	})
+}
+
+func (t *trackingResponseWriter) Header() http.Header {
+	return t.writer.Header()
+}
+
+func (t *trackingResponseWriter) Write(data []byte) (int, error) {
+	n, err := t.writer.Write(data)
+	t.respSize += int64(n)
+	// Add message event for request bytes sent.
+	span := trace.FromContext(t.ctx)
+	span.AddMessageSendEvent(0 /* TODO: messageID */, int64(n), -1)
+	return n, err
+}
+
+func (t *trackingResponseWriter) WriteHeader(statusCode int) {
+	t.writer.WriteHeader(statusCode)
+	t.statusCode = statusCode
+	t.statusLine = http.StatusText(t.statusCode)
+}
+
+// wrappedResponseWriter returns a wrapped version of the original
+//  ResponseWriter and only implements the same combination of additional
+// interfaces as the original.
+// This implementation is based on https://github.com/felixge/httpsnoop.
+func (t *trackingResponseWriter) wrappedResponseWriter() http.ResponseWriter {
+	var (
+		hj, i0 = t.writer.(http.Hijacker)
+		cn, i1 = t.writer.(http.CloseNotifier)
+		pu, i2 = t.writer.(http.Pusher)
+		fl, i3 = t.writer.(http.Flusher)
+		rf, i4 = t.writer.(io.ReaderFrom)
+	)
+
+	switch {
+	case !i0 && !i1 && !i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+		}{t}
+	case !i0 && !i1 && !i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			io.ReaderFrom
+		}{t, rf}
+	case !i0 && !i1 && !i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Flusher
+		}{t, fl}
+	case !i0 && !i1 && !i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Flusher
+			io.ReaderFrom
+		}{t, fl, rf}
+	case !i0 && !i1 && i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Pusher
+		}{t, pu}
+	case !i0 && !i1 && i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Pusher
+			io.ReaderFrom
+		}{t, pu, rf}
+	case !i0 && !i1 && i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Pusher
+			http.Flusher
+		}{t, pu, fl}
+	case !i0 && !i1 && i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Pusher
+			http.Flusher
+			io.ReaderFrom
+		}{t, pu, fl, rf}
+	case !i0 && i1 && !i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+		}{t, cn}
+	case !i0 && i1 && !i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			io.ReaderFrom
+		}{t, cn, rf}
+	case !i0 && i1 && !i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Flusher
+		}{t, cn, fl}
+	case !i0 && i1 && !i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Flusher
+			io.ReaderFrom
+		}{t, cn, fl, rf}
+	case !i0 && i1 && i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Pusher
+		}{t, cn, pu}
+	case !i0 && i1 && i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Pusher
+			io.ReaderFrom
+		}{t, cn, pu, rf}
+	case !i0 && i1 && i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Pusher
+			http.Flusher
+		}{t, cn, pu, fl}
+	case !i0 && i1 && i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.CloseNotifier
+			http.Pusher
+			http.Flusher
+			io.ReaderFrom
+		}{t, cn, pu, fl, rf}
+	case i0 && !i1 && !i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+		}{t, hj}
+	case i0 && !i1 && !i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			io.ReaderFrom
+		}{t, hj, rf}
+	case i0 && !i1 && !i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Flusher
+		}{t, hj, fl}
+	case i0 && !i1 && !i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Flusher
+			io.ReaderFrom
+		}{t, hj, fl, rf}
+	case i0 && !i1 && i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Pusher
+		}{t, hj, pu}
+	case i0 && !i1 && i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Pusher
+			io.ReaderFrom
+		}{t, hj, pu, rf}
+	case i0 && !i1 && i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Pusher
+			http.Flusher
+		}{t, hj, pu, fl}
+	case i0 && !i1 && i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.Pusher
+			http.Flusher
+			io.ReaderFrom
+		}{t, hj, pu, fl, rf}
+	case i0 && i1 && !i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+		}{t, hj, cn}
+	case i0 && i1 && !i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			io.ReaderFrom
+		}{t, hj, cn, rf}
+	case i0 && i1 && !i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Flusher
+		}{t, hj, cn, fl}
+	case i0 && i1 && !i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Flusher
+			io.ReaderFrom
+		}{t, hj, cn, fl, rf}
+	case i0 && i1 && i2 && !i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Pusher
+		}{t, hj, cn, pu}
+	case i0 && i1 && i2 && !i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Pusher
+			io.ReaderFrom
+		}{t, hj, cn, pu, rf}
+	case i0 && i1 && i2 && i3 && !i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Pusher
+			http.Flusher
+		}{t, hj, cn, pu, fl}
+	case i0 && i1 && i2 && i3 && i4:
+		return struct {
+			http.ResponseWriter
+			http.Hijacker
+			http.CloseNotifier
+			http.Pusher
+			http.Flusher
+			io.ReaderFrom
+		}{t, hj, cn, pu, fl, rf}
+	default:
+		return struct {
+			http.ResponseWriter
+		}{t}
+	}
+}

vendor/go.opencensus.io/plugin/ochttp/span_annotating_client_trace.go

@@ -0,0 +1,169 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"crypto/tls"
+	"net/http"
+	"net/http/httptrace"
+	"strings"
+
+	"go.opencensus.io/trace"
+)
+
+type spanAnnotator struct {
+	sp *trace.Span
+}
+
+// TODO: Remove NewSpanAnnotator at the next release.
+
+// NewSpanAnnotator returns a httptrace.ClientTrace which annotates
+// all emitted httptrace events on the provided Span.
+// Deprecated: Use NewSpanAnnotatingClientTrace instead
+func NewSpanAnnotator(r *http.Request, s *trace.Span) *httptrace.ClientTrace {
+	return NewSpanAnnotatingClientTrace(r, s)
+}
+
+// NewSpanAnnotatingClientTrace returns a httptrace.ClientTrace which annotates
+// all emitted httptrace events on the provided Span.
+func NewSpanAnnotatingClientTrace(_ *http.Request, s *trace.Span) *httptrace.ClientTrace {
+	sa := spanAnnotator{sp: s}
+
+	return &httptrace.ClientTrace{
+		GetConn:              sa.getConn,
+		GotConn:              sa.gotConn,
+		PutIdleConn:          sa.putIdleConn,
+		GotFirstResponseByte: sa.gotFirstResponseByte,
+		Got100Continue:       sa.got100Continue,
+		DNSStart:             sa.dnsStart,
+		DNSDone:              sa.dnsDone,
+		ConnectStart:         sa.connectStart,
+		ConnectDone:          sa.connectDone,
+		TLSHandshakeStart:    sa.tlsHandshakeStart,
+		TLSHandshakeDone:     sa.tlsHandshakeDone,
+		WroteHeaders:         sa.wroteHeaders,
+		Wait100Continue:      sa.wait100Continue,
+		WroteRequest:         sa.wroteRequest,
+	}
+}
+
+func (s spanAnnotator) getConn(hostPort string) {
+	attrs := []trace.Attribute{
+		trace.StringAttribute("httptrace.get_connection.host_port", hostPort),
+	}
+	s.sp.Annotate(attrs, "GetConn")
+}
+
+func (s spanAnnotator) gotConn(info httptrace.GotConnInfo) {
+	attrs := []trace.Attribute{
+		trace.BoolAttribute("httptrace.got_connection.reused", info.Reused),
+		trace.BoolAttribute("httptrace.got_connection.was_idle", info.WasIdle),
+	}
+	if info.WasIdle {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.got_connection.idle_time", info.IdleTime.String()))
+	}
+	s.sp.Annotate(attrs, "GotConn")
+}
+
+// PutIdleConn implements a httptrace.ClientTrace hook
+func (s spanAnnotator) putIdleConn(err error) {
+	var attrs []trace.Attribute
+	if err != nil {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.put_idle_connection.error", err.Error()))
+	}
+	s.sp.Annotate(attrs, "PutIdleConn")
+}
+
+func (s spanAnnotator) gotFirstResponseByte() {
+	s.sp.Annotate(nil, "GotFirstResponseByte")
+}
+
+func (s spanAnnotator) got100Continue() {
+	s.sp.Annotate(nil, "Got100Continue")
+}
+
+func (s spanAnnotator) dnsStart(info httptrace.DNSStartInfo) {
+	attrs := []trace.Attribute{
+		trace.StringAttribute("httptrace.dns_start.host", info.Host),
+	}
+	s.sp.Annotate(attrs, "DNSStart")
+}
+
+func (s spanAnnotator) dnsDone(info httptrace.DNSDoneInfo) {
+	var addrs []string
+	for _, addr := range info.Addrs {
+		addrs = append(addrs, addr.String())
+	}
+	attrs := []trace.Attribute{
+		trace.StringAttribute("httptrace.dns_done.addrs", strings.Join(addrs, " , ")),
+	}
+	if info.Err != nil {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.dns_done.error", info.Err.Error()))
+	}
+	s.sp.Annotate(attrs, "DNSDone")
+}
+
+func (s spanAnnotator) connectStart(network, addr string) {
+	attrs := []trace.Attribute{
+		trace.StringAttribute("httptrace.connect_start.network", network),
+		trace.StringAttribute("httptrace.connect_start.addr", addr),
+	}
+	s.sp.Annotate(attrs, "ConnectStart")
+}
+
+func (s spanAnnotator) connectDone(network, addr string, err error) {
+	attrs := []trace.Attribute{
+		trace.StringAttribute("httptrace.connect_done.network", network),
+		trace.StringAttribute("httptrace.connect_done.addr", addr),
+	}
+	if err != nil {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.connect_done.error", err.Error()))
+	}
+	s.sp.Annotate(attrs, "ConnectDone")
+}
+
+func (s spanAnnotator) tlsHandshakeStart() {
+	s.sp.Annotate(nil, "TLSHandshakeStart")
+}
+
+func (s spanAnnotator) tlsHandshakeDone(_ tls.ConnectionState, err error) {
+	var attrs []trace.Attribute
+	if err != nil {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.tls_handshake_done.error", err.Error()))
+	}
+	s.sp.Annotate(attrs, "TLSHandshakeDone")
+}
+
+func (s spanAnnotator) wroteHeaders() {
+	s.sp.Annotate(nil, "WroteHeaders")
+}
+
+func (s spanAnnotator) wait100Continue() {
+	s.sp.Annotate(nil, "Wait100Continue")
+}
+
+func (s spanAnnotator) wroteRequest(info httptrace.WroteRequestInfo) {
+	var attrs []trace.Attribute
+	if info.Err != nil {
+		attrs = append(attrs,
+			trace.StringAttribute("httptrace.wrote_request.error", info.Err.Error()))
+	}
+	s.sp.Annotate(attrs, "WroteRequest")
+}

vendor/go.opencensus.io/plugin/ochttp/stats.go

@@ -0,0 +1,292 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/view"
+	"go.opencensus.io/tag"
+)
+
+// Deprecated: client HTTP measures.
+var (
+	// Deprecated: Use a Count aggregation over one of the other client measures to achieve the same effect.
+	ClientRequestCount = stats.Int64(
+		"opencensus.io/http/client/request_count",
+		"Number of HTTP requests started",
+		stats.UnitDimensionless)
+	// Deprecated: Use ClientSentBytes.
+	ClientRequestBytes = stats.Int64(
+		"opencensus.io/http/client/request_bytes",
+		"HTTP request body size if set as ContentLength (uncompressed)",
+		stats.UnitBytes)
+	// Deprecated: Use ClientReceivedBytes.
+	ClientResponseBytes = stats.Int64(
+		"opencensus.io/http/client/response_bytes",
+		"HTTP response body size (uncompressed)",
+		stats.UnitBytes)
+	// Deprecated: Use ClientRoundtripLatency.
+	ClientLatency = stats.Float64(
+		"opencensus.io/http/client/latency",
+		"End-to-end latency",
+		stats.UnitMilliseconds)
+)
+
+// The following client HTTP measures are supported for use in custom views.
+var (
+	ClientSentBytes = stats.Int64(
+		"opencensus.io/http/client/sent_bytes",
+		"Total bytes sent in request body (not including headers)",
+		stats.UnitBytes,
+	)
+	ClientReceivedBytes = stats.Int64(
+		"opencensus.io/http/client/received_bytes",
+		"Total bytes received in response bodies (not including headers but including error responses with bodies)",
+		stats.UnitBytes,
+	)
+	ClientRoundtripLatency = stats.Float64(
+		"opencensus.io/http/client/roundtrip_latency",
+		"Time between first byte of request headers sent to last byte of response received, or terminal error",
+		stats.UnitMilliseconds,
+	)
+)
+
+// The following server HTTP measures are supported for use in custom views:
+var (
+	ServerRequestCount = stats.Int64(
+		"opencensus.io/http/server/request_count",
+		"Number of HTTP requests started",
+		stats.UnitDimensionless)
+	ServerRequestBytes = stats.Int64(
+		"opencensus.io/http/server/request_bytes",
+		"HTTP request body size if set as ContentLength (uncompressed)",
+		stats.UnitBytes)
+	ServerResponseBytes = stats.Int64(
+		"opencensus.io/http/server/response_bytes",
+		"HTTP response body size (uncompressed)",
+		stats.UnitBytes)
+	ServerLatency = stats.Float64(
+		"opencensus.io/http/server/latency",
+		"End-to-end latency",
+		stats.UnitMilliseconds)
+)
+
+// The following tags are applied to stats recorded by this package. Host, Path
+// and Method are applied to all measures. StatusCode is not applied to
+// ClientRequestCount or ServerRequestCount, since it is recorded before the status is known.
+var (
+	// Host is the value of the HTTP Host header.
+	//
+	// The value of this tag can be controlled by the HTTP client, so you need
+	// to watch out for potentially generating high-cardinality labels in your
+	// metrics backend if you use this tag in views.
+	Host = tag.MustNewKey("http.host")
+
+	// StatusCode is the numeric HTTP response status code,
+	// or "error" if a transport error occurred and no status code was read.
+	StatusCode = tag.MustNewKey("http.status")
+
+	// Path is the URL path (not including query string) in the request.
+	//
+	// The value of this tag can be controlled by the HTTP client, so you need
+	// to watch out for potentially generating high-cardinality labels in your
+	// metrics backend if you use this tag in views.
+	Path = tag.MustNewKey("http.path")
+
+	// Method is the HTTP method of the request, capitalized (GET, POST, etc.).
+	Method = tag.MustNewKey("http.method")
+
+	// KeyServerRoute is a low cardinality string representing the logical
+	// handler of the request. This is usually the pattern registered on the a
+	// ServeMux (or similar string).
+	KeyServerRoute = tag.MustNewKey("http_server_route")
+)
+
+// Client tag keys.
+var (
+	// KeyClientMethod is the HTTP method, capitalized (i.e. GET, POST, PUT, DELETE, etc.).
+	KeyClientMethod = tag.MustNewKey("http_client_method")
+	// KeyClientPath is the URL path (not including query string).
+	KeyClientPath = tag.MustNewKey("http_client_path")
+	// KeyClientStatus is the HTTP status code as an integer (e.g. 200, 404, 500.), or "error" if no response status line was received.
+	KeyClientStatus = tag.MustNewKey("http_client_status")
+	// KeyClientHost is the value of the request Host header.
+	KeyClientHost = tag.MustNewKey("http_client_host")
+)
+
+// Default distributions used by views in this package.
+var (
+	DefaultSizeDistribution    = view.Distribution(1024, 2048, 4096, 16384, 65536, 262144, 1048576, 4194304, 16777216, 67108864, 268435456, 1073741824, 4294967296)
+	DefaultLatencyDistribution = view.Distribution(1, 2, 3, 4, 5, 6, 8, 10, 13, 16, 20, 25, 30, 40, 50, 65, 80, 100, 130, 160, 200, 250, 300, 400, 500, 650, 800, 1000, 2000, 5000, 10000, 20000, 50000, 100000)
+)
+
+// Package ochttp provides some convenience views for client measures.
+// You still need to register these views for data to actually be collected.
+var (
+	ClientSentBytesDistribution = &view.View{
+		Name:        "opencensus.io/http/client/sent_bytes",
+		Measure:     ClientSentBytes,
+		Aggregation: DefaultSizeDistribution,
+		Description: "Total bytes sent in request body (not including headers), by HTTP method and response status",
+		TagKeys:     []tag.Key{KeyClientMethod, KeyClientStatus},
+	}
+
+	ClientReceivedBytesDistribution = &view.View{
+		Name:        "opencensus.io/http/client/received_bytes",
+		Measure:     ClientReceivedBytes,
+		Aggregation: DefaultSizeDistribution,
+		Description: "Total bytes received in response bodies (not including headers but including error responses with bodies), by HTTP method and response status",
+		TagKeys:     []tag.Key{KeyClientMethod, KeyClientStatus},
+	}
+
+	ClientRoundtripLatencyDistribution = &view.View{
+		Name:        "opencensus.io/http/client/roundtrip_latency",
+		Measure:     ClientRoundtripLatency,
+		Aggregation: DefaultLatencyDistribution,
+		Description: "End-to-end latency, by HTTP method and response status",
+		TagKeys:     []tag.Key{KeyClientMethod, KeyClientStatus},
+	}
+
+	ClientCompletedCount = &view.View{
+		Name:        "opencensus.io/http/client/completed_count",
+		Measure:     ClientRoundtripLatency,
+		Aggregation: view.Count(),
+		Description: "Count of completed requests, by HTTP method and response status",
+		TagKeys:     []tag.Key{KeyClientMethod, KeyClientStatus},
+	}
+)
+
+// Deprecated: Old client Views.
+var (
+	// Deprecated: No direct replacement, but see ClientCompletedCount.
+	ClientRequestCountView = &view.View{
+		Name:        "opencensus.io/http/client/request_count",
+		Description: "Count of HTTP requests started",
+		Measure:     ClientRequestCount,
+		Aggregation: view.Count(),
+	}
+
+	// Deprecated: Use ClientSentBytesDistribution.
+	ClientRequestBytesView = &view.View{
+		Name:        "opencensus.io/http/client/request_bytes",
+		Description: "Size distribution of HTTP request body",
+		Measure:     ClientSentBytes,
+		Aggregation: DefaultSizeDistribution,
+	}
+
+	// Deprecated: Use ClientReceivedBytesDistribution instead.
+	ClientResponseBytesView = &view.View{
+		Name:        "opencensus.io/http/client/response_bytes",
+		Description: "Size distribution of HTTP response body",
+		Measure:     ClientReceivedBytes,
+		Aggregation: DefaultSizeDistribution,
+	}
+
+	// Deprecated: Use ClientRoundtripLatencyDistribution instead.
+	ClientLatencyView = &view.View{
+		Name:        "opencensus.io/http/client/latency",
+		Description: "Latency distribution of HTTP requests",
+		Measure:     ClientRoundtripLatency,
+		Aggregation: DefaultLatencyDistribution,
+	}
+
+	// Deprecated: Use ClientCompletedCount instead.
+	ClientRequestCountByMethod = &view.View{
+		Name:        "opencensus.io/http/client/request_count_by_method",
+		Description: "Client request count by HTTP method",
+		TagKeys:     []tag.Key{Method},
+		Measure:     ClientSentBytes,
+		Aggregation: view.Count(),
+	}
+
+	// Deprecated: Use ClientCompletedCount instead.
+	ClientResponseCountByStatusCode = &view.View{
+		Name:        "opencensus.io/http/client/response_count_by_status_code",
+		Description: "Client response count by status code",
+		TagKeys:     []tag.Key{StatusCode},
+		Measure:     ClientRoundtripLatency,
+		Aggregation: view.Count(),
+	}
+)
+
+// Package ochttp provides some convenience views for server measures.
+// You still need to register these views for data to actually be collected.
+var (
+	ServerRequestCountView = &view.View{
+		Name:        "opencensus.io/http/server/request_count",
+		Description: "Count of HTTP requests started",
+		Measure:     ServerRequestCount,
+		Aggregation: view.Count(),
+	}
+
+	ServerRequestBytesView = &view.View{
+		Name:        "opencensus.io/http/server/request_bytes",
+		Description: "Size distribution of HTTP request body",
+		Measure:     ServerRequestBytes,
+		Aggregation: DefaultSizeDistribution,
+	}
+
+	ServerResponseBytesView = &view.View{
+		Name:        "opencensus.io/http/server/response_bytes",
+		Description: "Size distribution of HTTP response body",
+		Measure:     ServerResponseBytes,
+		Aggregation: DefaultSizeDistribution,
+	}
+
+	ServerLatencyView = &view.View{
+		Name:        "opencensus.io/http/server/latency",
+		Description: "Latency distribution of HTTP requests",
+		Measure:     ServerLatency,
+		Aggregation: DefaultLatencyDistribution,
+	}
+
+	ServerRequestCountByMethod = &view.View{
+		Name:        "opencensus.io/http/server/request_count_by_method",
+		Description: "Server request count by HTTP method",
+		TagKeys:     []tag.Key{Method},
+		Measure:     ServerRequestCount,
+		Aggregation: view.Count(),
+	}
+
+	ServerResponseCountByStatusCode = &view.View{
+		Name:        "opencensus.io/http/server/response_count_by_status_code",
+		Description: "Server response count by status code",
+		TagKeys:     []tag.Key{StatusCode},
+		Measure:     ServerLatency,
+		Aggregation: view.Count(),
+	}
+)
+
+// DefaultClientViews are the default client views provided by this package.
+// Deprecated: No replacement. Register the views you would like individually.
+var DefaultClientViews = []*view.View{
+	ClientRequestCountView,
+	ClientRequestBytesView,
+	ClientResponseBytesView,
+	ClientLatencyView,
+	ClientRequestCountByMethod,
+	ClientResponseCountByStatusCode,
+}
+
+// DefaultServerViews are the default server views provided by this package.
+// Deprecated: No replacement. Register the views you would like individually.
+var DefaultServerViews = []*view.View{
+	ServerRequestCountView,
+	ServerRequestBytesView,
+	ServerResponseBytesView,
+	ServerLatencyView,
+	ServerRequestCountByMethod,
+	ServerResponseCountByStatusCode,
+}

vendor/go.opencensus.io/plugin/ochttp/trace.go

@@ -0,0 +1,244 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptrace"
+
+	"go.opencensus.io/plugin/ochttp/propagation/b3"
+	"go.opencensus.io/trace"
+	"go.opencensus.io/trace/propagation"
+)
+
+// TODO(jbd): Add godoc examples.
+
+var defaultFormat propagation.HTTPFormat = &b3.HTTPFormat{}
+
+// Attributes recorded on the span for the requests.
+// Only trace exporters will need them.
+const (
+	HostAttribute       = "http.host"
+	MethodAttribute     = "http.method"
+	PathAttribute       = "http.path"
+	URLAttribute        = "http.url"
+	UserAgentAttribute  = "http.user_agent"
+	StatusCodeAttribute = "http.status_code"
+)
+
+type traceTransport struct {
+	base           http.RoundTripper
+	startOptions   trace.StartOptions
+	format         propagation.HTTPFormat
+	formatSpanName func(*http.Request) string
+	newClientTrace func(*http.Request, *trace.Span) *httptrace.ClientTrace
+}
+
+// TODO(jbd): Add message events for request and response size.
+
+// RoundTrip creates a trace.Span and inserts it into the outgoing request's headers.
+// The created span can follow a parent span, if a parent is presented in
+// the request's context.
+func (t *traceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	name := t.formatSpanName(req)
+	// TODO(jbd): Discuss whether we want to prefix
+	// outgoing requests with Sent.
+	ctx, span := trace.StartSpan(req.Context(), name,
+		trace.WithSampler(t.startOptions.Sampler),
+		trace.WithSpanKind(trace.SpanKindClient))
+
+	if t.newClientTrace != nil {
+		req = req.WithContext(httptrace.WithClientTrace(ctx, t.newClientTrace(req, span)))
+	} else {
+		req = req.WithContext(ctx)
+	}
+
+	if t.format != nil {
+		// SpanContextToRequest will modify its Request argument, which is
+		// contrary to the contract for http.RoundTripper, so we need to
+		// pass it a copy of the Request.
+		// However, the Request struct itself was already copied by
+		// the WithContext calls above and so we just need to copy the header.
+		header := make(http.Header)
+		for k, v := range req.Header {
+			header[k] = v
+		}
+		req.Header = header
+		t.format.SpanContextToRequest(span.SpanContext(), req)
+	}
+
+	span.AddAttributes(requestAttrs(req)...)
+	resp, err := t.base.RoundTrip(req)
+	if err != nil {
+		span.SetStatus(trace.Status{Code: trace.StatusCodeUnknown, Message: err.Error()})
+		span.End()
+		return resp, err
+	}
+
+	span.AddAttributes(responseAttrs(resp)...)
+	span.SetStatus(TraceStatus(resp.StatusCode, resp.Status))
+
+	// span.End() will be invoked after
+	// a read from resp.Body returns io.EOF or when
+	// resp.Body.Close() is invoked.
+	bt := &bodyTracker{rc: resp.Body, span: span}
+	resp.Body = wrappedBody(bt, resp.Body)
+	return resp, err
+}
+
+// bodyTracker wraps a response.Body and invokes
+// trace.EndSpan on encountering io.EOF on reading
+// the body of the original response.
+type bodyTracker struct {
+	rc   io.ReadCloser
+	span *trace.Span
+}
+
+var _ io.ReadCloser = (*bodyTracker)(nil)
+
+func (bt *bodyTracker) Read(b []byte) (int, error) {
+	n, err := bt.rc.Read(b)
+
+	switch err {
+	case nil:
+		return n, nil
+	case io.EOF:
+		bt.span.End()
+	default:
+		// For all other errors, set the span status
+		bt.span.SetStatus(trace.Status{
+			// Code 2 is the error code for Internal server error.
+			Code:    2,
+			Message: err.Error(),
+		})
+	}
+	return n, err
+}
+
+func (bt *bodyTracker) Close() error {
+	// Invoking endSpan on Close will help catch the cases
+	// in which a read returned a non-nil error, we set the
+	// span status but didn't end the span.
+	bt.span.End()
+	return bt.rc.Close()
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t *traceTransport) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := t.base.(canceler); ok {
+		cr.CancelRequest(req)
+	}
+}
+
+func spanNameFromURL(req *http.Request) string {
+	return req.URL.Path
+}
+
+func requestAttrs(r *http.Request) []trace.Attribute {
+	userAgent := r.UserAgent()
+
+	attrs := make([]trace.Attribute, 0, 5)
+	attrs = append(attrs,
+		trace.StringAttribute(PathAttribute, r.URL.Path),
+		trace.StringAttribute(URLAttribute, r.URL.String()),
+		trace.StringAttribute(HostAttribute, r.Host),
+		trace.StringAttribute(MethodAttribute, r.Method),
+	)
+
+	if userAgent != "" {
+		attrs = append(attrs, trace.StringAttribute(UserAgentAttribute, userAgent))
+	}
+
+	return attrs
+}
+
+func responseAttrs(resp *http.Response) []trace.Attribute {
+	return []trace.Attribute{
+		trace.Int64Attribute(StatusCodeAttribute, int64(resp.StatusCode)),
+	}
+}
+
+// TraceStatus is a utility to convert the HTTP status code to a trace.Status that
+// represents the outcome as closely as possible.
+func TraceStatus(httpStatusCode int, statusLine string) trace.Status {
+	var code int32
+	if httpStatusCode < 200 || httpStatusCode >= 400 {
+		code = trace.StatusCodeUnknown
+	}
+	switch httpStatusCode {
+	case 499:
+		code = trace.StatusCodeCancelled
+	case http.StatusBadRequest:
+		code = trace.StatusCodeInvalidArgument
+	case http.StatusUnprocessableEntity:
+		code = trace.StatusCodeInvalidArgument
+	case http.StatusGatewayTimeout:
+		code = trace.StatusCodeDeadlineExceeded
+	case http.StatusNotFound:
+		code = trace.StatusCodeNotFound
+	case http.StatusForbidden:
+		code = trace.StatusCodePermissionDenied
+	case http.StatusUnauthorized: // 401 is actually unauthenticated.
+		code = trace.StatusCodeUnauthenticated
+	case http.StatusTooManyRequests:
+		code = trace.StatusCodeResourceExhausted
+	case http.StatusNotImplemented:
+		code = trace.StatusCodeUnimplemented
+	case http.StatusServiceUnavailable:
+		code = trace.StatusCodeUnavailable
+	case http.StatusOK:
+		code = trace.StatusCodeOK
+	case http.StatusConflict:
+		code = trace.StatusCodeAlreadyExists
+	}
+
+	return trace.Status{Code: code, Message: codeToStr[code]}
+}
+
+var codeToStr = map[int32]string{
+	trace.StatusCodeOK:                 `OK`,
+	trace.StatusCodeCancelled:          `CANCELLED`,
+	trace.StatusCodeUnknown:            `UNKNOWN`,
+	trace.StatusCodeInvalidArgument:    `INVALID_ARGUMENT`,
+	trace.StatusCodeDeadlineExceeded:   `DEADLINE_EXCEEDED`,
+	trace.StatusCodeNotFound:           `NOT_FOUND`,
+	trace.StatusCodeAlreadyExists:      `ALREADY_EXISTS`,
+	trace.StatusCodePermissionDenied:   `PERMISSION_DENIED`,
+	trace.StatusCodeResourceExhausted:  `RESOURCE_EXHAUSTED`,
+	trace.StatusCodeFailedPrecondition: `FAILED_PRECONDITION`,
+	trace.StatusCodeAborted:            `ABORTED`,
+	trace.StatusCodeOutOfRange:         `OUT_OF_RANGE`,
+	trace.StatusCodeUnimplemented:      `UNIMPLEMENTED`,
+	trace.StatusCodeInternal:           `INTERNAL`,
+	trace.StatusCodeUnavailable:        `UNAVAILABLE`,
+	trace.StatusCodeDataLoss:           `DATA_LOSS`,
+	trace.StatusCodeUnauthenticated:    `UNAUTHENTICATED`,
+}
+
+func isHealthEndpoint(path string) bool {
+	// Health checking is pretty frequent and
+	// traces collected for health endpoints
+	// can be extremely noisy and expensive.
+	// Disable canonical health checking endpoints
+	// like /healthz and /_ah/health for now.
+	if path == "/healthz" || path == "/_ah/health" {
+		return true
+	}
+	return false
+}

vendor/go.opencensus.io/plugin/ochttp/wrapped_body.go

@@ -0,0 +1,44 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+	"io"
+)
+
+// wrappedBody returns a wrapped version of the original
+// Body and only implements the same combination of additional
+// interfaces as the original.
+func wrappedBody(wrapper io.ReadCloser, body io.ReadCloser) io.ReadCloser {
+	var (
+		wr, i0 = body.(io.Writer)
+	)
+	switch {
+	case !i0:
+		return struct {
+			io.ReadCloser
+		}{wrapper}
+
+	case i0:
+		return struct {
+			io.ReadCloser
+			io.Writer
+		}{wrapper, wr}
+	default:
+		return struct {
+			io.ReadCloser
+		}{wrapper}
+	}
+}

vendor/go.opencensus.io/resource/resource.go

@@ -0,0 +1,164 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package resource provides functionality for resource, which capture
+// identifying information about the entities for which signals are exported.
+package resource
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Environment variables used by FromEnv to decode a resource.
+const (
+	EnvVarType   = "OC_RESOURCE_TYPE"
+	EnvVarLabels = "OC_RESOURCE_LABELS"
+)
+
+// Resource describes an entity about which identifying information and metadata is exposed.
+// For example, a type "k8s.io/container" may hold labels describing the pod name and namespace.
+type Resource struct {
+	Type   string
+	Labels map[string]string
+}
+
+// EncodeLabels encodes a labels map to a string as provided via the OC_RESOURCE_LABELS environment variable.
+func EncodeLabels(labels map[string]string) string {
+	sortedKeys := make([]string, 0, len(labels))
+	for k := range labels {
+		sortedKeys = append(sortedKeys, k)
+	}
+	sort.Strings(sortedKeys)
+
+	s := ""
+	for i, k := range sortedKeys {
+		if i > 0 {
+			s += ","
+		}
+		s += k + "=" + strconv.Quote(labels[k])
+	}
+	return s
+}
+
+var labelRegex = regexp.MustCompile(`^\s*([[:ascii:]]{1,256}?)=("[[:ascii:]]{0,256}?")\s*,`)
+
+// DecodeLabels decodes a serialized label map as used in the OC_RESOURCE_LABELS variable.
+// A list of labels of the form `<key1>="<value1>",<key2>="<value2>",...` is accepted.
+// Domain names and paths are accepted as label keys.
+// Most users will want to use FromEnv instead.
+func DecodeLabels(s string) (map[string]string, error) {
+	m := map[string]string{}
+	// Ensure a trailing comma, which allows us to keep the regex simpler
+	s = strings.TrimRight(strings.TrimSpace(s), ",") + ","
+
+	for len(s) > 0 {
+		match := labelRegex.FindStringSubmatch(s)
+		if len(match) == 0 {
+			return nil, fmt.Errorf("invalid label formatting, remainder: %s", s)
+		}
+		v := match[2]
+		if v == "" {
+			v = match[3]
+		} else {
+			var err error
+			if v, err = strconv.Unquote(v); err != nil {
+				return nil, fmt.Errorf("invalid label formatting, remainder: %s, err: %s", s, err)
+			}
+		}
+		m[match[1]] = v
+
+		s = s[len(match[0]):]
+	}
+	return m, nil
+}
+
+// FromEnv is a detector that loads resource information from the OC_RESOURCE_TYPE
+// and OC_RESOURCE_labelS environment variables.
+func FromEnv(context.Context) (*Resource, error) {
+	res := &Resource{
+		Type: strings.TrimSpace(os.Getenv(EnvVarType)),
+	}
+	labels := strings.TrimSpace(os.Getenv(EnvVarLabels))
+	if labels == "" {
+		return res, nil
+	}
+	var err error
+	if res.Labels, err = DecodeLabels(labels); err != nil {
+		return nil, err
+	}
+	return res, nil
+}
+
+var _ Detector = FromEnv
+
+// merge resource information from b into a. In case of a collision, a takes precedence.
+func merge(a, b *Resource) *Resource {
+	if a == nil {
+		return b
+	}
+	if b == nil {
+		return a
+	}
+	res := &Resource{
+		Type:   a.Type,
+		Labels: map[string]string{},
+	}
+	if res.Type == "" {
+		res.Type = b.Type
+	}
+	for k, v := range b.Labels {
+		res.Labels[k] = v
+	}
+	// Labels from resource a overwrite labels from resource b.
+	for k, v := range a.Labels {
+		res.Labels[k] = v
+	}
+	return res
+}
+
+// Detector attempts to detect resource information.
+// If the detector cannot find resource information, the returned resource is nil but no
+// error is returned.
+// An error is only returned on unexpected failures.
+type Detector func(context.Context) (*Resource, error)
+
+// MultiDetector returns a Detector that calls all input detectors in order and
+// merges each result with the previous one. In case a type of label key is already set,
+// the first set value is takes precedence.
+// It returns on the first error that a sub-detector encounters.
+func MultiDetector(detectors ...Detector) Detector {
+	return func(ctx context.Context) (*Resource, error) {
+		return detectAll(ctx, detectors...)
+	}
+}
+
+// detectall calls all input detectors sequentially an merges each result with the previous one.
+// It returns on the first error that a sub-detector encounters.
+func detectAll(ctx context.Context, detectors ...Detector) (*Resource, error) {
+	var res *Resource
+	for _, d := range detectors {
+		r, err := d(ctx)
+		if err != nil {
+			return nil, err
+		}
+		res = merge(res, r)
+	}
+	return res, nil
+}

vendor/go.opencensus.io/stats/doc.go

@@ -0,0 +1,69 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+/*
+Package stats contains support for OpenCensus stats recording.
+
+OpenCensus allows users to create typed measures, record measurements,
+aggregate the collected data, and export the aggregated data.
+
+Measures
+
+A measure represents a type of data point to be tracked and recorded.
+For example, latency, request Mb/s, and response Mb/s are measures
+to collect from a server.
+
+Measure constructors such as Int64 and Float64 automatically
+register the measure by the given name. Each registered measure needs
+to be unique by name. Measures also have a description and a unit.
+
+Libraries can define and export measures. Application authors can then
+create views and collect and break down measures by the tags they are
+interested in.
+
+Recording measurements
+
+Measurement is a data point to be collected for a measure. For example,
+for a latency (ms) measure, 100 is a measurement that represents a 100ms
+latency event. Measurements are created from measures with
+the current context. Tags from the current context are recorded with the
+measurements if they are any.
+
+Recorded measurements are dropped immediately if no views are registered for them.
+There is usually no need to conditionally enable and disable
+recording to reduce cost. Recording of measurements is cheap.
+
+Libraries can always record measurements, and applications can later decide
+on which measurements they want to collect by registering views. This allows
+libraries to turn on the instrumentation by default.
+
+Exemplars
+
+For a given recorded measurement, the associated exemplar is a diagnostic map
+that gives more information about the measurement.
+
+When aggregated using a Distribution aggregation, an exemplar is kept for each
+bucket in the Distribution. This allows you to easily find an example of a
+measurement that fell into each bucket.
+
+For example, if you also use the OpenCensus trace package and you
+record a measurement with a context that contains a sampled trace span,
+then the trace span will be added to the exemplar associated with the measurement.
+
+When exported to a supporting back end, you should be able to easily navigate
+to example traces that fell into each bucket in the Distribution.
+
+*/
+package stats // import "go.opencensus.io/stats"

vendor/go.opencensus.io/stats/internal/record.go

@@ -0,0 +1,25 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"go.opencensus.io/tag"
+)
+
+// DefaultRecorder will be called for each Record call.
+var DefaultRecorder func(tags *tag.Map, measurement interface{}, attachments map[string]interface{})
+
+// SubscriptionReporter reports when a view subscribed with a measure.
+var SubscriptionReporter func(measure string)

vendor/go.opencensus.io/stats/measure.go

@@ -0,0 +1,109 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package stats
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// Measure represents a single numeric value to be tracked and recorded.
+// For example, latency, request bytes, and response bytes could be measures
+// to collect from a server.
+//
+// Measures by themselves have no outside effects. In order to be exported,
+// the measure needs to be used in a View. If no Views are defined over a
+// measure, there is very little cost in recording it.
+type Measure interface {
+	// Name returns the name of this measure.
+	//
+	// Measure names are globally unique (among all libraries linked into your program).
+	// We recommend prefixing the measure name with a domain name relevant to your
+	// project or application.
+	//
+	// Measure names are never sent over the wire or exported to backends.
+	// They are only used to create Views.
+	Name() string
+
+	// Description returns the human-readable description of this measure.
+	Description() string
+
+	// Unit returns the units for the values this measure takes on.
+	//
+	// Units are encoded according to the case-sensitive abbreviations from the
+	// Unified Code for Units of Measure: http://unitsofmeasure.org/ucum.html
+	Unit() string
+}
+
+// measureDescriptor is the untyped descriptor associated with each measure.
+// Int64Measure and Float64Measure wrap measureDescriptor to provide typed
+// recording APIs.
+// Two Measures with the same name will have the same measureDescriptor.
+type measureDescriptor struct {
+	subs int32 // access atomically
+
+	name        string
+	description string
+	unit        string
+}
+
+func (m *measureDescriptor) subscribe() {
+	atomic.StoreInt32(&m.subs, 1)
+}
+
+func (m *measureDescriptor) subscribed() bool {
+	return atomic.LoadInt32(&m.subs) == 1
+}
+
+var (
+	mu       sync.RWMutex
+	measures = make(map[string]*measureDescriptor)
+)
+
+func registerMeasureHandle(name, desc, unit string) *measureDescriptor {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if stored, ok := measures[name]; ok {
+		return stored
+	}
+	m := &measureDescriptor{
+		name:        name,
+		description: desc,
+		unit:        unit,
+	}
+	measures[name] = m
+	return m
+}
+
+// Measurement is the numeric value measured when recording stats. Each measure
+// provides methods to create measurements of their kind. For example, Int64Measure
+// provides M to convert an int64 into a measurement.
+type Measurement struct {
+	v    float64
+	m    Measure
+	desc *measureDescriptor
+}
+
+// Value returns the value of the Measurement as a float64.
+func (m Measurement) Value() float64 {
+	return m.v
+}
+
+// Measure returns the Measure from which this Measurement was created.
+func (m Measurement) Measure() Measure {
+	return m.m
+}

vendor/go.opencensus.io/stats/measure_float64.go

@@ -0,0 +1,55 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package stats
+
+// Float64Measure is a measure for float64 values.
+type Float64Measure struct {
+	desc *measureDescriptor
+}
+
+// M creates a new float64 measurement.
+// Use Record to record measurements.
+func (m *Float64Measure) M(v float64) Measurement {
+	return Measurement{
+		m:    m,
+		desc: m.desc,
+		v:    v,
+	}
+}
+
+// Float64 creates a new measure for float64 values.
+//
+// See the documentation for interface Measure for more guidance on the
+// parameters of this function.
+func Float64(name, description, unit string) *Float64Measure {
+	mi := registerMeasureHandle(name, description, unit)
+	return &Float64Measure{mi}
+}
+
+// Name returns the name of the measure.
+func (m *Float64Measure) Name() string {
+	return m.desc.name
+}
+
+// Description returns the description of the measure.
+func (m *Float64Measure) Description() string {
+	return m.desc.description
+}
+
+// Unit returns the unit of the measure.
+func (m *Float64Measure) Unit() string {
+	return m.desc.unit
+}

vendor/go.opencensus.io/stats/measure_int64.go

@@ -0,0 +1,55 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package stats
+
+// Int64Measure is a measure for int64 values.
+type Int64Measure struct {
+	desc *measureDescriptor
+}
+
+// M creates a new int64 measurement.
+// Use Record to record measurements.
+func (m *Int64Measure) M(v int64) Measurement {
+	return Measurement{
+		m:    m,
+		desc: m.desc,
+		v:    float64(v),
+	}
+}
+
+// Int64 creates a new measure for int64 values.
+//
+// See the documentation for interface Measure for more guidance on the
+// parameters of this function.
+func Int64(name, description, unit string) *Int64Measure {
+	mi := registerMeasureHandle(name, description, unit)
+	return &Int64Measure{mi}
+}
+
+// Name returns the name of the measure.
+func (m *Int64Measure) Name() string {
+	return m.desc.name
+}
+
+// Description returns the description of the measure.
+func (m *Int64Measure) Description() string {
+	return m.desc.description
+}
+
+// Unit returns the unit of the measure.
+func (m *Int64Measure) Unit() string {
+	return m.desc.unit
+}

vendor/go.opencensus.io/stats/record.go

@@ -0,0 +1,137 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package stats
+
+import (
+	"context"
+
+	"go.opencensus.io/metric/metricdata"
+	"go.opencensus.io/stats/internal"
+	"go.opencensus.io/tag"
+)
+
+func init() {
+	internal.SubscriptionReporter = func(measure string) {
+		mu.Lock()
+		measures[measure].subscribe()
+		mu.Unlock()
+	}
+}
+
+// Recorder provides an interface for exporting measurement information from
+// the static Record method by using the WithRecorder option.
+type Recorder interface {
+	// Record records a set of measurements associated with the given tags and attachments.
+	// The second argument is a `[]Measurement`.
+	Record(*tag.Map, interface{}, map[string]interface{})
+}
+
+type recordOptions struct {
+	attachments  metricdata.Attachments
+	mutators     []tag.Mutator
+	measurements []Measurement
+	recorder     Recorder
+}
+
+// WithAttachments applies provided exemplar attachments.
+func WithAttachments(attachments metricdata.Attachments) Options {
+	return func(ro *recordOptions) {
+		ro.attachments = attachments
+	}
+}
+
+// WithTags applies provided tag mutators.
+func WithTags(mutators ...tag.Mutator) Options {
+	return func(ro *recordOptions) {
+		ro.mutators = mutators
+	}
+}
+
+// WithMeasurements applies provided measurements.
+func WithMeasurements(measurements ...Measurement) Options {
+	return func(ro *recordOptions) {
+		ro.measurements = measurements
+	}
+}
+
+// WithRecorder records the measurements to the specified `Recorder`, rather
+// than to the global metrics recorder.
+func WithRecorder(meter Recorder) Options {
+	return func(ro *recordOptions) {
+		ro.recorder = meter
+	}
+}
+
+// Options apply changes to recordOptions.
+type Options func(*recordOptions)
+
+func createRecordOption(ros ...Options) *recordOptions {
+	o := &recordOptions{}
+	for _, ro := range ros {
+		ro(o)
+	}
+	return o
+}
+
+// Record records one or multiple measurements with the same context at once.
+// If there are any tags in the context, measurements will be tagged with them.
+func Record(ctx context.Context, ms ...Measurement) {
+	RecordWithOptions(ctx, WithMeasurements(ms...))
+}
+
+// RecordWithTags records one or multiple measurements at once.
+//
+// Measurements will be tagged with the tags in the context mutated by the mutators.
+// RecordWithTags is useful if you want to record with tag mutations but don't want
+// to propagate the mutations in the context.
+func RecordWithTags(ctx context.Context, mutators []tag.Mutator, ms ...Measurement) error {
+	return RecordWithOptions(ctx, WithTags(mutators...), WithMeasurements(ms...))
+}
+
+// RecordWithOptions records measurements from the given options (if any) against context
+// and tags and attachments in the options (if any).
+// If there are any tags in the context, measurements will be tagged with them.
+func RecordWithOptions(ctx context.Context, ros ...Options) error {
+	o := createRecordOption(ros...)
+	if len(o.measurements) == 0 {
+		return nil
+	}
+	recorder := internal.DefaultRecorder
+	if o.recorder != nil {
+		recorder = o.recorder.Record
+	}
+	if recorder == nil {
+		return nil
+	}
+	record := false
+	for _, m := range o.measurements {
+		if m.desc.subscribed() {
+			record = true
+			break
+		}
+	}
+	if !record {
+		return nil
+	}
+	if len(o.mutators) > 0 {
+		var err error
+		if ctx, err = tag.New(ctx, o.mutators...); err != nil {
+			return err
+		}
+	}
+	recorder(tag.FromContext(ctx), o.measurements, o.attachments)
+	return nil
+}

vendor/go.opencensus.io/stats/units.go

@@ -0,0 +1,26 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package stats
+
+// Units are encoded according to the case-sensitive abbreviations from the
+// Unified Code for Units of Measure: http://unitsofmeasure.org/ucum.html
+const (
+	UnitNone          = "1" // Deprecated: Use UnitDimensionless.
+	UnitDimensionless = "1"
+	UnitBytes         = "By"
+	UnitMilliseconds  = "ms"
+	UnitSeconds       = "s"
+)

vendor/go.opencensus.io/stats/view/aggregation.go

@@ -0,0 +1,121 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+// AggType represents the type of aggregation function used on a View.
+type AggType int
+
+// All available aggregation types.
+const (
+	AggTypeNone         AggType = iota // no aggregation; reserved for future use.
+	AggTypeCount                       // the count aggregation, see Count.
+	AggTypeSum                         // the sum aggregation, see Sum.
+	AggTypeDistribution                // the distribution aggregation, see Distribution.
+	AggTypeLastValue                   // the last value aggregation, see LastValue.
+)
+
+func (t AggType) String() string {
+	return aggTypeName[t]
+}
+
+var aggTypeName = map[AggType]string{
+	AggTypeNone:         "None",
+	AggTypeCount:        "Count",
+	AggTypeSum:          "Sum",
+	AggTypeDistribution: "Distribution",
+	AggTypeLastValue:    "LastValue",
+}
+
+// Aggregation represents a data aggregation method. Use one of the functions:
+// Count, Sum, or Distribution to construct an Aggregation.
+type Aggregation struct {
+	Type    AggType   // Type is the AggType of this Aggregation.
+	Buckets []float64 // Buckets are the bucket endpoints if this Aggregation represents a distribution, see Distribution.
+
+	newData func() AggregationData
+}
+
+var (
+	aggCount = &Aggregation{
+		Type: AggTypeCount,
+		newData: func() AggregationData {
+			return &CountData{}
+		},
+	}
+	aggSum = &Aggregation{
+		Type: AggTypeSum,
+		newData: func() AggregationData {
+			return &SumData{}
+		},
+	}
+)
+
+// Count indicates that data collected and aggregated
+// with this method will be turned into a count value.
+// For example, total number of accepted requests can be
+// aggregated by using Count.
+func Count() *Aggregation {
+	return aggCount
+}
+
+// Sum indicates that data collected and aggregated
+// with this method will be summed up.
+// For example, accumulated request bytes can be aggregated by using
+// Sum.
+func Sum() *Aggregation {
+	return aggSum
+}
+
+// Distribution indicates that the desired aggregation is
+// a histogram distribution.
+//
+// A distribution aggregation may contain a histogram of the values in the
+// population. The bucket boundaries for that histogram are described
+// by the bounds. This defines len(bounds)+1 buckets.
+//
+// If len(bounds) >= 2 then the boundaries for bucket index i are:
+//
+//     [-infinity, bounds[i]) for i = 0
+//     [bounds[i-1], bounds[i]) for 0 < i < length
+//     [bounds[i-1], +infinity) for i = length
+//
+// If len(bounds) is 0 then there is no histogram associated with the
+// distribution. There will be a single bucket with boundaries
+// (-infinity, +infinity).
+//
+// If len(bounds) is 1 then there is no finite buckets, and that single
+// element is the common boundary of the overflow and underflow buckets.
+func Distribution(bounds ...float64) *Aggregation {
+	agg := &Aggregation{
+		Type:    AggTypeDistribution,
+		Buckets: bounds,
+	}
+	agg.newData = func() AggregationData {
+		return newDistributionData(agg)
+	}
+	return agg
+}
+
+// LastValue only reports the last value recorded using this
+// aggregation. All other measurements will be dropped.
+func LastValue() *Aggregation {
+	return &Aggregation{
+		Type: AggTypeLastValue,
+		newData: func() AggregationData {
+			return &LastValueData{}
+		},
+	}
+}

vendor/go.opencensus.io/stats/view/aggregation_data.go

@@ -0,0 +1,293 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"math"
+	"time"
+
+	"go.opencensus.io/metric/metricdata"
+)
+
+// AggregationData represents an aggregated value from a collection.
+// They are reported on the view data during exporting.
+// Mosts users won't directly access aggregration data.
+type AggregationData interface {
+	isAggregationData() bool
+	addSample(v float64, attachments map[string]interface{}, t time.Time)
+	clone() AggregationData
+	equal(other AggregationData) bool
+	toPoint(t metricdata.Type, time time.Time) metricdata.Point
+}
+
+const epsilon = 1e-9
+
+// CountData is the aggregated data for the Count aggregation.
+// A count aggregation processes data and counts the recordings.
+//
+// Most users won't directly access count data.
+type CountData struct {
+	Value int64
+}
+
+func (a *CountData) isAggregationData() bool { return true }
+
+func (a *CountData) addSample(_ float64, _ map[string]interface{}, _ time.Time) {
+	a.Value = a.Value + 1
+}
+
+func (a *CountData) clone() AggregationData {
+	return &CountData{Value: a.Value}
+}
+
+func (a *CountData) equal(other AggregationData) bool {
+	a2, ok := other.(*CountData)
+	if !ok {
+		return false
+	}
+
+	return a.Value == a2.Value
+}
+
+func (a *CountData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
+	switch metricType {
+	case metricdata.TypeCumulativeInt64:
+		return metricdata.NewInt64Point(t, a.Value)
+	default:
+		panic("unsupported metricdata.Type")
+	}
+}
+
+// SumData is the aggregated data for the Sum aggregation.
+// A sum aggregation processes data and sums up the recordings.
+//
+// Most users won't directly access sum data.
+type SumData struct {
+	Value float64
+}
+
+func (a *SumData) isAggregationData() bool { return true }
+
+func (a *SumData) addSample(v float64, _ map[string]interface{}, _ time.Time) {
+	a.Value += v
+}
+
+func (a *SumData) clone() AggregationData {
+	return &SumData{Value: a.Value}
+}
+
+func (a *SumData) equal(other AggregationData) bool {
+	a2, ok := other.(*SumData)
+	if !ok {
+		return false
+	}
+	return math.Pow(a.Value-a2.Value, 2) < epsilon
+}
+
+func (a *SumData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
+	switch metricType {
+	case metricdata.TypeCumulativeInt64:
+		return metricdata.NewInt64Point(t, int64(a.Value))
+	case metricdata.TypeCumulativeFloat64:
+		return metricdata.NewFloat64Point(t, a.Value)
+	default:
+		panic("unsupported metricdata.Type")
+	}
+}
+
+// DistributionData is the aggregated data for the
+// Distribution aggregation.
+//
+// Most users won't directly access distribution data.
+//
+// For a distribution with N bounds, the associated DistributionData will have
+// N+1 buckets.
+type DistributionData struct {
+	Count           int64   // number of data points aggregated
+	Min             float64 // minimum value in the distribution
+	Max             float64 // max value in the distribution
+	Mean            float64 // mean of the distribution
+	SumOfSquaredDev float64 // sum of the squared deviation from the mean
+	CountPerBucket  []int64 // number of occurrences per bucket
+	// ExemplarsPerBucket is slice the same length as CountPerBucket containing
+	// an exemplar for the associated bucket, or nil.
+	ExemplarsPerBucket []*metricdata.Exemplar
+	bounds             []float64 // histogram distribution of the values
+}
+
+func newDistributionData(agg *Aggregation) *DistributionData {
+	bucketCount := len(agg.Buckets) + 1
+	return &DistributionData{
+		CountPerBucket:     make([]int64, bucketCount),
+		ExemplarsPerBucket: make([]*metricdata.Exemplar, bucketCount),
+		bounds:             agg.Buckets,
+		Min:                math.MaxFloat64,
+		Max:                math.SmallestNonzeroFloat64,
+	}
+}
+
+// Sum returns the sum of all samples collected.
+func (a *DistributionData) Sum() float64 { return a.Mean * float64(a.Count) }
+
+func (a *DistributionData) variance() float64 {
+	if a.Count <= 1 {
+		return 0
+	}
+	return a.SumOfSquaredDev / float64(a.Count-1)
+}
+
+func (a *DistributionData) isAggregationData() bool { return true }
+
+// TODO(songy23): support exemplar attachments.
+func (a *DistributionData) addSample(v float64, attachments map[string]interface{}, t time.Time) {
+	if v < a.Min {
+		a.Min = v
+	}
+	if v > a.Max {
+		a.Max = v
+	}
+	a.Count++
+	a.addToBucket(v, attachments, t)
+
+	if a.Count == 1 {
+		a.Mean = v
+		return
+	}
+
+	oldMean := a.Mean
+	a.Mean = a.Mean + (v-a.Mean)/float64(a.Count)
+	a.SumOfSquaredDev = a.SumOfSquaredDev + (v-oldMean)*(v-a.Mean)
+}
+
+func (a *DistributionData) addToBucket(v float64, attachments map[string]interface{}, t time.Time) {
+	var count *int64
+	var i int
+	var b float64
+	for i, b = range a.bounds {
+		if v < b {
+			count = &a.CountPerBucket[i]
+			break
+		}
+	}
+	if count == nil { // Last bucket.
+		i = len(a.bounds)
+		count = &a.CountPerBucket[i]
+	}
+	*count++
+	if exemplar := getExemplar(v, attachments, t); exemplar != nil {
+		a.ExemplarsPerBucket[i] = exemplar
+	}
+}
+
+func getExemplar(v float64, attachments map[string]interface{}, t time.Time) *metricdata.Exemplar {
+	if len(attachments) == 0 {
+		return nil
+	}
+	return &metricdata.Exemplar{
+		Value:       v,
+		Timestamp:   t,
+		Attachments: attachments,
+	}
+}
+
+func (a *DistributionData) clone() AggregationData {
+	c := *a
+	c.CountPerBucket = append([]int64(nil), a.CountPerBucket...)
+	c.ExemplarsPerBucket = append([]*metricdata.Exemplar(nil), a.ExemplarsPerBucket...)
+	return &c
+}
+
+func (a *DistributionData) equal(other AggregationData) bool {
+	a2, ok := other.(*DistributionData)
+	if !ok {
+		return false
+	}
+	if a2 == nil {
+		return false
+	}
+	if len(a.CountPerBucket) != len(a2.CountPerBucket) {
+		return false
+	}
+	for i := range a.CountPerBucket {
+		if a.CountPerBucket[i] != a2.CountPerBucket[i] {
+			return false
+		}
+	}
+	return a.Count == a2.Count && a.Min == a2.Min && a.Max == a2.Max && math.Pow(a.Mean-a2.Mean, 2) < epsilon && math.Pow(a.variance()-a2.variance(), 2) < epsilon
+}
+
+func (a *DistributionData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
+	switch metricType {
+	case metricdata.TypeCumulativeDistribution:
+		buckets := []metricdata.Bucket{}
+		for i := 0; i < len(a.CountPerBucket); i++ {
+			buckets = append(buckets, metricdata.Bucket{
+				Count:    a.CountPerBucket[i],
+				Exemplar: a.ExemplarsPerBucket[i],
+			})
+		}
+		bucketOptions := &metricdata.BucketOptions{Bounds: a.bounds}
+
+		val := &metricdata.Distribution{
+			Count:                 a.Count,
+			Sum:                   a.Sum(),
+			SumOfSquaredDeviation: a.SumOfSquaredDev,
+			BucketOptions:         bucketOptions,
+			Buckets:               buckets,
+		}
+		return metricdata.NewDistributionPoint(t, val)
+
+	default:
+		// TODO: [rghetia] when we have a use case for TypeGaugeDistribution.
+		panic("unsupported metricdata.Type")
+	}
+}
+
+// LastValueData returns the last value recorded for LastValue aggregation.
+type LastValueData struct {
+	Value float64
+}
+
+func (l *LastValueData) isAggregationData() bool {
+	return true
+}
+
+func (l *LastValueData) addSample(v float64, _ map[string]interface{}, _ time.Time) {
+	l.Value = v
+}
+
+func (l *LastValueData) clone() AggregationData {
+	return &LastValueData{l.Value}
+}
+
+func (l *LastValueData) equal(other AggregationData) bool {
+	a2, ok := other.(*LastValueData)
+	if !ok {
+		return false
+	}
+	return l.Value == a2.Value
+}
+
+func (l *LastValueData) toPoint(metricType metricdata.Type, t time.Time) metricdata.Point {
+	switch metricType {
+	case metricdata.TypeGaugeInt64:
+		return metricdata.NewInt64Point(t, int64(l.Value))
+	case metricdata.TypeGaugeFloat64:
+		return metricdata.NewFloat64Point(t, l.Value)
+	default:
+		panic("unsupported metricdata.Type")
+	}
+}

vendor/go.opencensus.io/stats/view/collector.go

@@ -0,0 +1,86 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"sort"
+	"time"
+
+	"go.opencensus.io/internal/tagencoding"
+	"go.opencensus.io/tag"
+)
+
+type collector struct {
+	// signatures holds the aggregations values for each unique tag signature
+	// (values for all keys) to its aggregator.
+	signatures map[string]AggregationData
+	// Aggregation is the description of the aggregation to perform for this
+	// view.
+	a *Aggregation
+}
+
+func (c *collector) addSample(s string, v float64, attachments map[string]interface{}, t time.Time) {
+	aggregator, ok := c.signatures[s]
+	if !ok {
+		aggregator = c.a.newData()
+		c.signatures[s] = aggregator
+	}
+	aggregator.addSample(v, attachments, t)
+}
+
+// collectRows returns a snapshot of the collected Row values.
+func (c *collector) collectedRows(keys []tag.Key) []*Row {
+	rows := make([]*Row, 0, len(c.signatures))
+	for sig, aggregator := range c.signatures {
+		tags := decodeTags([]byte(sig), keys)
+		row := &Row{Tags: tags, Data: aggregator.clone()}
+		rows = append(rows, row)
+	}
+	return rows
+}
+
+func (c *collector) clearRows() {
+	c.signatures = make(map[string]AggregationData)
+}
+
+// encodeWithKeys encodes the map by using values
+// only associated with the keys provided.
+func encodeWithKeys(m *tag.Map, keys []tag.Key) []byte {
+	vb := &tagencoding.Values{
+		Buffer: make([]byte, len(keys)),
+	}
+	for _, k := range keys {
+		v, _ := m.Value(k)
+		vb.WriteValue([]byte(v))
+	}
+	return vb.Bytes()
+}
+
+// decodeTags decodes tags from the buffer and
+// orders them by the keys.
+func decodeTags(buf []byte, keys []tag.Key) []tag.Tag {
+	vb := &tagencoding.Values{Buffer: buf}
+	var tags []tag.Tag
+	for _, k := range keys {
+		v := vb.ReadValue()
+		if v != nil {
+			tags = append(tags, tag.Tag{Key: k, Value: string(v)})
+		}
+	}
+	vb.ReadIndex = 0
+	sort.Slice(tags, func(i, j int) bool { return tags[i].Key.Name() < tags[j].Key.Name() })
+	return tags
+}

vendor/go.opencensus.io/stats/view/doc.go

@@ -0,0 +1,47 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// Package view contains support for collecting and exposing aggregates over stats.
+//
+// In order to collect measurements, views need to be defined and registered.
+// A view allows recorded measurements to be filtered and aggregated.
+//
+// All recorded measurements can be grouped by a list of tags.
+//
+// OpenCensus provides several aggregation methods: Count, Distribution and Sum.
+//
+// Count only counts the number of measurement points recorded.
+// Distribution provides statistical summary of the aggregated data by counting
+// how many recorded measurements fall into each bucket.
+// Sum adds up the measurement values.
+// LastValue just keeps track of the most recently recorded measurement value.
+// All aggregations are cumulative.
+//
+// Views can be registered and unregistered at any time during program execution.
+//
+// Libraries can define views but it is recommended that in most cases registering
+// views be left up to applications.
+//
+// Exporting
+//
+// Collected and aggregated data can be exported to a metric collection
+// backend by registering its exporter.
+//
+// Multiple exporters can be registered to upload the data to various
+// different back ends.
+package view // import "go.opencensus.io/stats/view"
+
+// TODO(acetechnologist): Add a link to the language independent OpenCensus
+// spec when it is available.

vendor/go.opencensus.io/stats/view/export.go

@@ -0,0 +1,45 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package view
+
+// Exporter exports the collected records as view data.
+//
+// The ExportView method should return quickly; if an
+// Exporter takes a significant amount of time to
+// process a Data, that work should be done on another goroutine.
+//
+// It is safe to assume that ExportView will not be called concurrently from
+// multiple goroutines.
+//
+// The Data should not be modified.
+type Exporter interface {
+	ExportView(viewData *Data)
+}
+
+// RegisterExporter registers an exporter.
+// Collected data will be reported via all the
+// registered exporters. Once you no longer
+// want data to be exported, invoke UnregisterExporter
+// with the previously registered exporter.
+//
+// Binaries can register exporters, libraries shouldn't register exporters.
+func RegisterExporter(e Exporter) {
+	defaultWorker.RegisterExporter(e)
+}
+
+// UnregisterExporter unregisters an exporter.
+func UnregisterExporter(e Exporter) {
+	defaultWorker.UnregisterExporter(e)
+}

vendor/go.opencensus.io/stats/view/view.go

@@ -0,0 +1,221 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"reflect"
+	"sort"
+	"sync/atomic"
+	"time"
+
+	"go.opencensus.io/metric/metricdata"
+	"go.opencensus.io/stats"
+	"go.opencensus.io/tag"
+)
+
+// View allows users to aggregate the recorded stats.Measurements.
+// Views need to be passed to the Register function before data will be
+// collected and sent to Exporters.
+type View struct {
+	Name        string // Name of View. Must be unique. If unset, will default to the name of the Measure.
+	Description string // Description is a human-readable description for this view.
+
+	// TagKeys are the tag keys describing the grouping of this view.
+	// A single Row will be produced for each combination of associated tag values.
+	TagKeys []tag.Key
+
+	// Measure is a stats.Measure to aggregate in this view.
+	Measure stats.Measure
+
+	// Aggregation is the aggregation function to apply to the set of Measurements.
+	Aggregation *Aggregation
+}
+
+// WithName returns a copy of the View with a new name. This is useful for
+// renaming views to cope with limitations placed on metric names by various
+// backends.
+func (v *View) WithName(name string) *View {
+	vNew := *v
+	vNew.Name = name
+	return &vNew
+}
+
+// same compares two views and returns true if they represent the same aggregation.
+func (v *View) same(other *View) bool {
+	if v == other {
+		return true
+	}
+	if v == nil {
+		return false
+	}
+	return reflect.DeepEqual(v.Aggregation, other.Aggregation) &&
+		v.Measure.Name() == other.Measure.Name()
+}
+
+// ErrNegativeBucketBounds error returned if histogram contains negative bounds.
+//
+// Deprecated: this should not be public.
+var ErrNegativeBucketBounds = errors.New("negative bucket bounds not supported")
+
+// canonicalize canonicalizes v by setting explicit
+// defaults for Name and Description and sorting the TagKeys
+func (v *View) canonicalize() error {
+	if v.Measure == nil {
+		return fmt.Errorf("cannot register view %q: measure not set", v.Name)
+	}
+	if v.Aggregation == nil {
+		return fmt.Errorf("cannot register view %q: aggregation not set", v.Name)
+	}
+	if v.Name == "" {
+		v.Name = v.Measure.Name()
+	}
+	if v.Description == "" {
+		v.Description = v.Measure.Description()
+	}
+	if err := checkViewName(v.Name); err != nil {
+		return err
+	}
+	sort.Slice(v.TagKeys, func(i, j int) bool {
+		return v.TagKeys[i].Name() < v.TagKeys[j].Name()
+	})
+	sort.Float64s(v.Aggregation.Buckets)
+	for _, b := range v.Aggregation.Buckets {
+		if b < 0 {
+			return ErrNegativeBucketBounds
+		}
+	}
+	// drop 0 bucket silently.
+	v.Aggregation.Buckets = dropZeroBounds(v.Aggregation.Buckets...)
+
+	return nil
+}
+
+func dropZeroBounds(bounds ...float64) []float64 {
+	for i, bound := range bounds {
+		if bound > 0 {
+			return bounds[i:]
+		}
+	}
+	return []float64{}
+}
+
+// viewInternal is the internal representation of a View.
+type viewInternal struct {
+	view             *View  // view is the canonicalized View definition associated with this view.
+	subscribed       uint32 // 1 if someone is subscribed and data need to be exported, use atomic to access
+	collector        *collector
+	metricDescriptor *metricdata.Descriptor
+}
+
+func newViewInternal(v *View) (*viewInternal, error) {
+	return &viewInternal{
+		view:             v,
+		collector:        &collector{make(map[string]AggregationData), v.Aggregation},
+		metricDescriptor: viewToMetricDescriptor(v),
+	}, nil
+}
+
+func (v *viewInternal) subscribe() {
+	atomic.StoreUint32(&v.subscribed, 1)
+}
+
+func (v *viewInternal) unsubscribe() {
+	atomic.StoreUint32(&v.subscribed, 0)
+}
+
+// isSubscribed returns true if the view is exporting
+// data by subscription.
+func (v *viewInternal) isSubscribed() bool {
+	return atomic.LoadUint32(&v.subscribed) == 1
+}
+
+func (v *viewInternal) clearRows() {
+	v.collector.clearRows()
+}
+
+func (v *viewInternal) collectedRows() []*Row {
+	return v.collector.collectedRows(v.view.TagKeys)
+}
+
+func (v *viewInternal) addSample(m *tag.Map, val float64, attachments map[string]interface{}, t time.Time) {
+	if !v.isSubscribed() {
+		return
+	}
+	sig := string(encodeWithKeys(m, v.view.TagKeys))
+	v.collector.addSample(sig, val, attachments, t)
+}
+
+// A Data is a set of rows about usage of the single measure associated
+// with the given view. Each row is specific to a unique set of tags.
+type Data struct {
+	View       *View
+	Start, End time.Time
+	Rows       []*Row
+}
+
+// Row is the collected value for a specific set of key value pairs a.k.a tags.
+type Row struct {
+	Tags []tag.Tag
+	Data AggregationData
+}
+
+func (r *Row) String() string {
+	var buffer bytes.Buffer
+	buffer.WriteString("{ ")
+	buffer.WriteString("{ ")
+	for _, t := range r.Tags {
+		buffer.WriteString(fmt.Sprintf("{%v %v}", t.Key.Name(), t.Value))
+	}
+	buffer.WriteString(" }")
+	buffer.WriteString(fmt.Sprintf("%v", r.Data))
+	buffer.WriteString(" }")
+	return buffer.String()
+}
+
+// Equal returns true if both rows are equal. Tags are expected to be ordered
+// by the key name. Even if both rows have the same tags but the tags appear in
+// different orders it will return false.
+func (r *Row) Equal(other *Row) bool {
+	if r == other {
+		return true
+	}
+	return reflect.DeepEqual(r.Tags, other.Tags) && r.Data.equal(other.Data)
+}
+
+const maxNameLength = 255
+
+// Returns true if the given string contains only printable characters.
+func isPrintable(str string) bool {
+	for _, r := range str {
+		if !(r >= ' ' && r <= '~') {
+			return false
+		}
+	}
+	return true
+}
+
+func checkViewName(name string) error {
+	if len(name) > maxNameLength {
+		return fmt.Errorf("view name cannot be larger than %v", maxNameLength)
+	}
+	if !isPrintable(name) {
+		return fmt.Errorf("view name needs to be an ASCII string")
+	}
+	return nil
+}

vendor/go.opencensus.io/stats/view/view_to_metric.go

@@ -0,0 +1,152 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"time"
+
+	"go.opencensus.io/resource"
+
+	"go.opencensus.io/metric/metricdata"
+	"go.opencensus.io/stats"
+)
+
+func getUnit(unit string) metricdata.Unit {
+	switch unit {
+	case "1":
+		return metricdata.UnitDimensionless
+	case "ms":
+		return metricdata.UnitMilliseconds
+	case "By":
+		return metricdata.UnitBytes
+	}
+	return metricdata.UnitDimensionless
+}
+
+func getType(v *View) metricdata.Type {
+	m := v.Measure
+	agg := v.Aggregation
+
+	switch agg.Type {
+	case AggTypeSum:
+		switch m.(type) {
+		case *stats.Int64Measure:
+			return metricdata.TypeCumulativeInt64
+		case *stats.Float64Measure:
+			return metricdata.TypeCumulativeFloat64
+		default:
+			panic("unexpected measure type")
+		}
+	case AggTypeDistribution:
+		return metricdata.TypeCumulativeDistribution
+	case AggTypeLastValue:
+		switch m.(type) {
+		case *stats.Int64Measure:
+			return metricdata.TypeGaugeInt64
+		case *stats.Float64Measure:
+			return metricdata.TypeGaugeFloat64
+		default:
+			panic("unexpected measure type")
+		}
+	case AggTypeCount:
+		switch m.(type) {
+		case *stats.Int64Measure:
+			return metricdata.TypeCumulativeInt64
+		case *stats.Float64Measure:
+			return metricdata.TypeCumulativeInt64
+		default:
+			panic("unexpected measure type")
+		}
+	default:
+		panic("unexpected aggregation type")
+	}
+}
+
+func getLabelKeys(v *View) []metricdata.LabelKey {
+	labelKeys := []metricdata.LabelKey{}
+	for _, k := range v.TagKeys {
+		labelKeys = append(labelKeys, metricdata.LabelKey{Key: k.Name()})
+	}
+	return labelKeys
+}
+
+func viewToMetricDescriptor(v *View) *metricdata.Descriptor {
+	return &metricdata.Descriptor{
+		Name:        v.Name,
+		Description: v.Description,
+		Unit:        convertUnit(v),
+		Type:        getType(v),
+		LabelKeys:   getLabelKeys(v),
+	}
+}
+
+func convertUnit(v *View) metricdata.Unit {
+	switch v.Aggregation.Type {
+	case AggTypeCount:
+		return metricdata.UnitDimensionless
+	default:
+		return getUnit(v.Measure.Unit())
+	}
+}
+
+func toLabelValues(row *Row, expectedKeys []metricdata.LabelKey) []metricdata.LabelValue {
+	labelValues := []metricdata.LabelValue{}
+	tagMap := make(map[string]string)
+	for _, tag := range row.Tags {
+		tagMap[tag.Key.Name()] = tag.Value
+	}
+
+	for _, key := range expectedKeys {
+		if val, ok := tagMap[key.Key]; ok {
+			labelValues = append(labelValues, metricdata.NewLabelValue(val))
+		} else {
+			labelValues = append(labelValues, metricdata.LabelValue{})
+		}
+	}
+	return labelValues
+}
+
+func rowToTimeseries(v *viewInternal, row *Row, now time.Time, startTime time.Time) *metricdata.TimeSeries {
+	return &metricdata.TimeSeries{
+		Points:      []metricdata.Point{row.Data.toPoint(v.metricDescriptor.Type, now)},
+		LabelValues: toLabelValues(row, v.metricDescriptor.LabelKeys),
+		StartTime:   startTime,
+	}
+}
+
+func viewToMetric(v *viewInternal, r *resource.Resource, now time.Time, startTime time.Time) *metricdata.Metric {
+	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
+		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {
+		startTime = time.Time{}
+	}
+
+	rows := v.collectedRows()
+	if len(rows) == 0 {
+		return nil
+	}
+
+	ts := []*metricdata.TimeSeries{}
+	for _, row := range rows {
+		ts = append(ts, rowToTimeseries(v, row, now, startTime))
+	}
+
+	m := &metricdata.Metric{
+		Descriptor: *v.metricDescriptor,
+		TimeSeries: ts,
+		Resource:   r,
+	}
+	return m
+}

vendor/go.opencensus.io/stats/view/worker.go

@@ -0,0 +1,413 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"go.opencensus.io/resource"
+
+	"go.opencensus.io/metric/metricdata"
+	"go.opencensus.io/metric/metricproducer"
+	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/internal"
+	"go.opencensus.io/tag"
+)
+
+func init() {
+	defaultWorker = NewMeter().(*worker)
+	go defaultWorker.start()
+	internal.DefaultRecorder = record
+}
+
+type measureRef struct {
+	measure string
+	views   map[*viewInternal]struct{}
+}
+
+type worker struct {
+	measures   map[string]*measureRef
+	views      map[string]*viewInternal
+	startTimes map[*viewInternal]time.Time
+
+	timer      *time.Ticker
+	c          chan command
+	quit, done chan bool
+	mu         sync.RWMutex
+	r          *resource.Resource
+
+	exportersMu sync.RWMutex
+	exporters   map[Exporter]struct{}
+}
+
+// Meter defines an interface which allows a single process to maintain
+// multiple sets of metrics exports (intended for the advanced case where a
+// single process wants to report metrics about multiple objects, such as
+// multiple databases or HTTP services).
+//
+// Note that this is an advanced use case, and the static functions in this
+// module should cover the common use cases.
+type Meter interface {
+	stats.Recorder
+	// Find returns a registered view associated with this name.
+	// If no registered view is found, nil is returned.
+	Find(name string) *View
+	// Register begins collecting data for the given views.
+	// Once a view is registered, it reports data to the registered exporters.
+	Register(views ...*View) error
+	// Unregister the given views. Data will not longer be exported for these views
+	// after Unregister returns.
+	// It is not necessary to unregister from views you expect to collect for the
+	// duration of your program execution.
+	Unregister(views ...*View)
+	// SetReportingPeriod sets the interval between reporting aggregated views in
+	// the program. If duration is less than or equal to zero, it enables the
+	// default behavior.
+	//
+	// Note: each exporter makes different promises about what the lowest supported
+	// duration is. For example, the Stackdriver exporter recommends a value no
+	// lower than 1 minute. Consult each exporter per your needs.
+	SetReportingPeriod(time.Duration)
+
+	// RegisterExporter registers an exporter.
+	// Collected data will be reported via all the
+	// registered exporters. Once you no longer
+	// want data to be exported, invoke UnregisterExporter
+	// with the previously registered exporter.
+	//
+	// Binaries can register exporters, libraries shouldn't register exporters.
+	RegisterExporter(Exporter)
+	// UnregisterExporter unregisters an exporter.
+	UnregisterExporter(Exporter)
+	// SetResource may be used to set the Resource associated with this registry.
+	// This is intended to be used in cases where a single process exports metrics
+	// for multiple Resources, typically in a multi-tenant situation.
+	SetResource(*resource.Resource)
+
+	// Start causes the Meter to start processing Record calls and aggregating
+	// statistics as well as exporting data.
+	Start()
+	// Stop causes the Meter to stop processing calls and terminate data export.
+	Stop()
+
+	// RetrieveData gets a snapshot of the data collected for the the view registered
+	// with the given name. It is intended for testing only.
+	RetrieveData(viewName string) ([]*Row, error)
+}
+
+var _ Meter = (*worker)(nil)
+
+var defaultWorker *worker
+
+var defaultReportingDuration = 10 * time.Second
+
+// Find returns a registered view associated with this name.
+// If no registered view is found, nil is returned.
+func Find(name string) (v *View) {
+	return defaultWorker.Find(name)
+}
+
+// Find returns a registered view associated with this name.
+// If no registered view is found, nil is returned.
+func (w *worker) Find(name string) (v *View) {
+	req := &getViewByNameReq{
+		name: name,
+		c:    make(chan *getViewByNameResp),
+	}
+	w.c <- req
+	resp := <-req.c
+	return resp.v
+}
+
+// Register begins collecting data for the given views.
+// Once a view is registered, it reports data to the registered exporters.
+func Register(views ...*View) error {
+	return defaultWorker.Register(views...)
+}
+
+// Register begins collecting data for the given views.
+// Once a view is registered, it reports data to the registered exporters.
+func (w *worker) Register(views ...*View) error {
+	req := &registerViewReq{
+		views: views,
+		err:   make(chan error),
+	}
+	w.c <- req
+	return <-req.err
+}
+
+// Unregister the given views. Data will not longer be exported for these views
+// after Unregister returns.
+// It is not necessary to unregister from views you expect to collect for the
+// duration of your program execution.
+func Unregister(views ...*View) {
+	defaultWorker.Unregister(views...)
+}
+
+// Unregister the given views. Data will not longer be exported for these views
+// after Unregister returns.
+// It is not necessary to unregister from views you expect to collect for the
+// duration of your program execution.
+func (w *worker) Unregister(views ...*View) {
+	names := make([]string, len(views))
+	for i := range views {
+		names[i] = views[i].Name
+	}
+	req := &unregisterFromViewReq{
+		views: names,
+		done:  make(chan struct{}),
+	}
+	w.c <- req
+	<-req.done
+}
+
+// RetrieveData gets a snapshot of the data collected for the the view registered
+// with the given name. It is intended for testing only.
+func RetrieveData(viewName string) ([]*Row, error) {
+	return defaultWorker.RetrieveData(viewName)
+}
+
+// RetrieveData gets a snapshot of the data collected for the the view registered
+// with the given name. It is intended for testing only.
+func (w *worker) RetrieveData(viewName string) ([]*Row, error) {
+	req := &retrieveDataReq{
+		now: time.Now(),
+		v:   viewName,
+		c:   make(chan *retrieveDataResp),
+	}
+	w.c <- req
+	resp := <-req.c
+	return resp.rows, resp.err
+}
+
+func record(tags *tag.Map, ms interface{}, attachments map[string]interface{}) {
+	defaultWorker.Record(tags, ms, attachments)
+}
+
+// Record records a set of measurements ms associated with the given tags and attachments.
+func (w *worker) Record(tags *tag.Map, ms interface{}, attachments map[string]interface{}) {
+	req := &recordReq{
+		tm:          tags,
+		ms:          ms.([]stats.Measurement),
+		attachments: attachments,
+		t:           time.Now(),
+	}
+	w.c <- req
+}
+
+// SetReportingPeriod sets the interval between reporting aggregated views in
+// the program. If duration is less than or equal to zero, it enables the
+// default behavior.
+//
+// Note: each exporter makes different promises about what the lowest supported
+// duration is. For example, the Stackdriver exporter recommends a value no
+// lower than 1 minute. Consult each exporter per your needs.
+func SetReportingPeriod(d time.Duration) {
+	defaultWorker.SetReportingPeriod(d)
+}
+
+// SetReportingPeriod sets the interval between reporting aggregated views in
+// the program. If duration is less than or equal to zero, it enables the
+// default behavior.
+//
+// Note: each exporter makes different promises about what the lowest supported
+// duration is. For example, the Stackdriver exporter recommends a value no
+// lower than 1 minute. Consult each exporter per your needs.
+func (w *worker) SetReportingPeriod(d time.Duration) {
+	// TODO(acetechnologist): ensure that the duration d is more than a certain
+	// value. e.g. 1s
+	req := &setReportingPeriodReq{
+		d: d,
+		c: make(chan bool),
+	}
+	w.c <- req
+	<-req.c // don't return until the timer is set to the new duration.
+}
+
+// NewMeter constructs a Meter instance. You should only need to use this if
+// you need to separate out Measurement recordings and View aggregations within
+// a single process.
+func NewMeter() Meter {
+	return &worker{
+		measures:   make(map[string]*measureRef),
+		views:      make(map[string]*viewInternal),
+		startTimes: make(map[*viewInternal]time.Time),
+		timer:      time.NewTicker(defaultReportingDuration),
+		c:          make(chan command, 1024),
+		quit:       make(chan bool),
+		done:       make(chan bool),
+
+		exporters: make(map[Exporter]struct{}),
+	}
+}
+
+// SetResource associates all data collected by this Meter with the specified
+// resource. This resource is reported when using metricexport.ReadAndExport;
+// it is not provided when used with ExportView/RegisterExporter, because that
+// interface does not provide a means for reporting the Resource.
+func (w *worker) SetResource(r *resource.Resource) {
+	w.r = r
+}
+
+func (w *worker) Start() {
+	go w.start()
+}
+
+func (w *worker) start() {
+	prodMgr := metricproducer.GlobalManager()
+	prodMgr.AddProducer(w)
+
+	for {
+		select {
+		case cmd := <-w.c:
+			cmd.handleCommand(w)
+		case <-w.timer.C:
+			w.reportUsage()
+		case <-w.quit:
+			w.timer.Stop()
+			close(w.c)
+			w.done <- true
+			return
+		}
+	}
+}
+
+func (w *worker) Stop() {
+	prodMgr := metricproducer.GlobalManager()
+	prodMgr.DeleteProducer(w)
+
+	w.quit <- true
+	<-w.done
+}
+
+func (w *worker) getMeasureRef(name string) *measureRef {
+	if mr, ok := w.measures[name]; ok {
+		return mr
+	}
+	mr := &measureRef{
+		measure: name,
+		views:   make(map[*viewInternal]struct{}),
+	}
+	w.measures[name] = mr
+	return mr
+}
+
+func (w *worker) tryRegisterView(v *View) (*viewInternal, error) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	vi, err := newViewInternal(v)
+	if err != nil {
+		return nil, err
+	}
+	if x, ok := w.views[vi.view.Name]; ok {
+		if !x.view.same(vi.view) {
+			return nil, fmt.Errorf("cannot register view %q; a different view with the same name is already registered", v.Name)
+		}
+
+		// the view is already registered so there is nothing to do and the
+		// command is considered successful.
+		return x, nil
+	}
+	w.views[vi.view.Name] = vi
+	w.startTimes[vi] = time.Now()
+	ref := w.getMeasureRef(vi.view.Measure.Name())
+	ref.views[vi] = struct{}{}
+	return vi, nil
+}
+
+func (w *worker) unregisterView(v *viewInternal) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	delete(w.views, v.view.Name)
+	delete(w.startTimes, v)
+	if measure := w.measures[v.view.Measure.Name()]; measure != nil {
+		delete(measure.views, v)
+	}
+}
+
+func (w *worker) reportView(v *viewInternal) {
+	if !v.isSubscribed() {
+		return
+	}
+	rows := v.collectedRows()
+	viewData := &Data{
+		View:  v.view,
+		Start: w.startTimes[v],
+		End:   time.Now(),
+		Rows:  rows,
+	}
+	w.exportersMu.Lock()
+	defer w.exportersMu.Unlock()
+	for e := range w.exporters {
+		e.ExportView(viewData)
+	}
+}
+
+func (w *worker) reportUsage() {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	for _, v := range w.views {
+		w.reportView(v)
+	}
+}
+
+func (w *worker) toMetric(v *viewInternal, now time.Time) *metricdata.Metric {
+	if !v.isSubscribed() {
+		return nil
+	}
+
+	var startTime time.Time
+	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
+		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {
+		startTime = time.Time{}
+	} else {
+		startTime = w.startTimes[v]
+	}
+
+	return viewToMetric(v, w.r, now, startTime)
+}
+
+// Read reads all view data and returns them as metrics.
+// It is typically invoked by metric reader to export stats in metric format.
+func (w *worker) Read() []*metricdata.Metric {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	now := time.Now()
+	metrics := make([]*metricdata.Metric, 0, len(w.views))
+	for _, v := range w.views {
+		metric := w.toMetric(v, now)
+		if metric != nil {
+			metrics = append(metrics, metric)
+		}
+	}
+	return metrics
+}
+
+func (w *worker) RegisterExporter(e Exporter) {
+	w.exportersMu.Lock()
+	defer w.exportersMu.Unlock()
+
+	w.exporters[e] = struct{}{}
+}
+
+func (w *worker) UnregisterExporter(e Exporter) {
+	w.exportersMu.Lock()
+	defer w.exportersMu.Unlock()
+
+	delete(w.exporters, e)
+}

vendor/go.opencensus.io/stats/view/worker_commands.go

@@ -0,0 +1,186 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package view
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"go.opencensus.io/stats"
+	"go.opencensus.io/stats/internal"
+	"go.opencensus.io/tag"
+)
+
+type command interface {
+	handleCommand(w *worker)
+}
+
+// getViewByNameReq is the command to get a view given its name.
+type getViewByNameReq struct {
+	name string
+	c    chan *getViewByNameResp
+}
+
+type getViewByNameResp struct {
+	v *View
+}
+
+func (cmd *getViewByNameReq) handleCommand(w *worker) {
+	v := w.views[cmd.name]
+	if v == nil {
+		cmd.c <- &getViewByNameResp{nil}
+		return
+	}
+	cmd.c <- &getViewByNameResp{v.view}
+}
+
+// registerViewReq is the command to register a view.
+type registerViewReq struct {
+	views []*View
+	err   chan error
+}
+
+func (cmd *registerViewReq) handleCommand(w *worker) {
+	for _, v := range cmd.views {
+		if err := v.canonicalize(); err != nil {
+			cmd.err <- err
+			return
+		}
+	}
+	var errstr []string
+	for _, view := range cmd.views {
+		vi, err := w.tryRegisterView(view)
+		if err != nil {
+			errstr = append(errstr, fmt.Sprintf("%s: %v", view.Name, err))
+			continue
+		}
+		internal.SubscriptionReporter(view.Measure.Name())
+		vi.subscribe()
+	}
+	if len(errstr) > 0 {
+		cmd.err <- errors.New(strings.Join(errstr, "\n"))
+	} else {
+		cmd.err <- nil
+	}
+}
+
+// unregisterFromViewReq is the command to unregister to a view. Has no
+// impact on the data collection for client that are pulling data from the
+// library.
+type unregisterFromViewReq struct {
+	views []string
+	done  chan struct{}
+}
+
+func (cmd *unregisterFromViewReq) handleCommand(w *worker) {
+	for _, name := range cmd.views {
+		vi, ok := w.views[name]
+		if !ok {
+			continue
+		}
+
+		// Report pending data for this view before removing it.
+		w.reportView(vi)
+
+		vi.unsubscribe()
+		if !vi.isSubscribed() {
+			// this was the last subscription and view is not collecting anymore.
+			// The collected data can be cleared.
+			vi.clearRows()
+		}
+		w.unregisterView(vi)
+	}
+	cmd.done <- struct{}{}
+}
+
+// retrieveDataReq is the command to retrieve data for a view.
+type retrieveDataReq struct {
+	now time.Time
+	v   string
+	c   chan *retrieveDataResp
+}
+
+type retrieveDataResp struct {
+	rows []*Row
+	err  error
+}
+
+func (cmd *retrieveDataReq) handleCommand(w *worker) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	vi, ok := w.views[cmd.v]
+	if !ok {
+		cmd.c <- &retrieveDataResp{
+			nil,
+			fmt.Errorf("cannot retrieve data; view %q is not registered", cmd.v),
+		}
+		return
+	}
+
+	if !vi.isSubscribed() {
+		cmd.c <- &retrieveDataResp{
+			nil,
+			fmt.Errorf("cannot retrieve data; view %q has no subscriptions or collection is not forcibly started", cmd.v),
+		}
+		return
+	}
+	cmd.c <- &retrieveDataResp{
+		vi.collectedRows(),
+		nil,
+	}
+}
+
+// recordReq is the command to record data related to multiple measures
+// at once.
+type recordReq struct {
+	tm          *tag.Map
+	ms          []stats.Measurement
+	attachments map[string]interface{}
+	t           time.Time
+}
+
+func (cmd *recordReq) handleCommand(w *worker) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	for _, m := range cmd.ms {
+		if (m == stats.Measurement{}) { // not registered
+			continue
+		}
+		ref := w.getMeasureRef(m.Measure().Name())
+		for v := range ref.views {
+			v.addSample(cmd.tm, m.Value(), cmd.attachments, cmd.t)
+		}
+	}
+}
+
+// setReportingPeriodReq is the command to modify the duration between
+// reporting the collected data to the registered clients.
+type setReportingPeriodReq struct {
+	d time.Duration
+	c chan bool
+}
+
+func (cmd *setReportingPeriodReq) handleCommand(w *worker) {
+	w.timer.Stop()
+	if cmd.d <= 0 {
+		w.timer = time.NewTicker(defaultReportingDuration)
+	} else {
+		w.timer = time.NewTicker(cmd.d)
+	}
+	cmd.c <- true
+}

vendor/go.opencensus.io/tag/context.go

@@ -0,0 +1,43 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package tag
+
+import (
+	"context"
+)
+
+// FromContext returns the tag map stored in the context.
+func FromContext(ctx context.Context) *Map {
+	// The returned tag map shouldn't be mutated.
+	ts := ctx.Value(mapCtxKey)
+	if ts == nil {
+		return nil
+	}
+	return ts.(*Map)
+}
+
+// NewContext creates a new context with the given tag map.
+// To propagate a tag map to downstream methods and downstream RPCs, add a tag map
+// to the current context. NewContext will return a copy of the current context,
+// and put the tag map into the returned one.
+// If there is already a tag map in the current context, it will be replaced with m.
+func NewContext(ctx context.Context, m *Map) context.Context {
+	return context.WithValue(ctx, mapCtxKey, m)
+}
+
+type ctxKey struct{}
+
+var mapCtxKey = ctxKey{}

vendor/go.opencensus.io/tag/doc.go

@@ -0,0 +1,26 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+/*
+Package tag contains OpenCensus tags.
+
+Tags are key-value pairs. Tags provide additional cardinality to
+the OpenCensus instrumentation data.
+
+Tags can be propagated on the wire and in the same
+process via context.Context. Encode and Decode should be
+used to represent tags into their binary propagation form.
+*/
+package tag // import "go.opencensus.io/tag"

vendor/go.opencensus.io/tag/key.go

@@ -0,0 +1,44 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package tag
+
+// Key represents a tag key.
+type Key struct {
+	name string
+}
+
+// NewKey creates or retrieves a string key identified by name.
+// Calling NewKey more than once with the same name returns the same key.
+func NewKey(name string) (Key, error) {
+	if !checkKeyName(name) {
+		return Key{}, errInvalidKeyName
+	}
+	return Key{name: name}, nil
+}
+
+// MustNewKey returns a key with the given name, and panics if name is an invalid key name.
+func MustNewKey(name string) Key {
+	k, err := NewKey(name)
+	if err != nil {
+		panic(err)
+	}
+	return k
+}
+
+// Name returns the name of the key.
+func (k Key) Name() string {
+	return k.name
+}

vendor/go.opencensus.io/tag/map.go

@@ -0,0 +1,229 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package tag
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"sort"
+)
+
+// Tag is a key value pair that can be propagated on wire.
+type Tag struct {
+	Key   Key
+	Value string
+}
+
+type tagContent struct {
+	value string
+	m     metadatas
+}
+
+// Map is a map of tags. Use New to create a context containing
+// a new Map.
+type Map struct {
+	m map[Key]tagContent
+}
+
+// Value returns the value for the key if a value for the key exists.
+func (m *Map) Value(k Key) (string, bool) {
+	if m == nil {
+		return "", false
+	}
+	v, ok := m.m[k]
+	return v.value, ok
+}
+
+func (m *Map) String() string {
+	if m == nil {
+		return "nil"
+	}
+	keys := make([]Key, 0, len(m.m))
+	for k := range m.m {
+		keys = append(keys, k)
+	}
+	sort.Slice(keys, func(i, j int) bool { return keys[i].Name() < keys[j].Name() })
+
+	var buffer bytes.Buffer
+	buffer.WriteString("{ ")
+	for _, k := range keys {
+		buffer.WriteString(fmt.Sprintf("{%v %v}", k.name, m.m[k]))
+	}
+	buffer.WriteString(" }")
+	return buffer.String()
+}
+
+func (m *Map) insert(k Key, v string, md metadatas) {
+	if _, ok := m.m[k]; ok {
+		return
+	}
+	m.m[k] = tagContent{value: v, m: md}
+}
+
+func (m *Map) update(k Key, v string, md metadatas) {
+	if _, ok := m.m[k]; ok {
+		m.m[k] = tagContent{value: v, m: md}
+	}
+}
+
+func (m *Map) upsert(k Key, v string, md metadatas) {
+	m.m[k] = tagContent{value: v, m: md}
+}
+
+func (m *Map) delete(k Key) {
+	delete(m.m, k)
+}
+
+func newMap() *Map {
+	return &Map{m: make(map[Key]tagContent)}
+}
+
+// Mutator modifies a tag map.
+type Mutator interface {
+	Mutate(t *Map) (*Map, error)
+}
+
+// Insert returns a mutator that inserts a
+// value associated with k. If k already exists in the tag map,
+// mutator doesn't update the value.
+// Metadata applies metadata to the tag. It is optional.
+// Metadatas are applied in the order in which it is provided.
+// If more than one metadata updates the same attribute then
+// the update from the last metadata prevails.
+func Insert(k Key, v string, mds ...Metadata) Mutator {
+	return &mutator{
+		fn: func(m *Map) (*Map, error) {
+			if !checkValue(v) {
+				return nil, errInvalidValue
+			}
+			m.insert(k, v, createMetadatas(mds...))
+			return m, nil
+		},
+	}
+}
+
+// Update returns a mutator that updates the
+// value of the tag associated with k with v. If k doesn't
+// exists in the tag map, the mutator doesn't insert the value.
+// Metadata applies metadata to the tag. It is optional.
+// Metadatas are applied in the order in which it is provided.
+// If more than one metadata updates the same attribute then
+// the update from the last metadata prevails.
+func Update(k Key, v string, mds ...Metadata) Mutator {
+	return &mutator{
+		fn: func(m *Map) (*Map, error) {
+			if !checkValue(v) {
+				return nil, errInvalidValue
+			}
+			m.update(k, v, createMetadatas(mds...))
+			return m, nil
+		},
+	}
+}
+
+// Upsert returns a mutator that upserts the
+// value of the tag associated with k with v. It inserts the
+// value if k doesn't exist already. It mutates the value
+// if k already exists.
+// Metadata applies metadata to the tag. It is optional.
+// Metadatas are applied in the order in which it is provided.
+// If more than one metadata updates the same attribute then
+// the update from the last metadata prevails.
+func Upsert(k Key, v string, mds ...Metadata) Mutator {
+	return &mutator{
+		fn: func(m *Map) (*Map, error) {
+			if !checkValue(v) {
+				return nil, errInvalidValue
+			}
+			m.upsert(k, v, createMetadatas(mds...))
+			return m, nil
+		},
+	}
+}
+
+func createMetadatas(mds ...Metadata) metadatas {
+	var metas metadatas
+	if len(mds) > 0 {
+		for _, md := range mds {
+			if md != nil {
+				md(&metas)
+			}
+		}
+	} else {
+		WithTTL(TTLUnlimitedPropagation)(&metas)
+	}
+	return metas
+
+}
+
+// Delete returns a mutator that deletes
+// the value associated with k.
+func Delete(k Key) Mutator {
+	return &mutator{
+		fn: func(m *Map) (*Map, error) {
+			m.delete(k)
+			return m, nil
+		},
+	}
+}
+
+// New returns a new context that contains a tag map
+// originated from the incoming context and modified
+// with the provided mutators.
+func New(ctx context.Context, mutator ...Mutator) (context.Context, error) {
+	m := newMap()
+	orig := FromContext(ctx)
+	if orig != nil {
+		for k, v := range orig.m {
+			if !checkKeyName(k.Name()) {
+				return ctx, fmt.Errorf("key:%q: %v", k, errInvalidKeyName)
+			}
+			if !checkValue(v.value) {
+				return ctx, fmt.Errorf("key:%q value:%q: %v", k.Name(), v, errInvalidValue)
+			}
+			m.insert(k, v.value, v.m)
+		}
+	}
+	var err error
+	for _, mod := range mutator {
+		m, err = mod.Mutate(m)
+		if err != nil {
+			return ctx, err
+		}
+	}
+	return NewContext(ctx, m), nil
+}
+
+// Do is similar to pprof.Do: a convenience for installing the tags
+// from the context as Go profiler labels. This allows you to
+// correlated runtime profiling with stats.
+//
+// It converts the key/values from the given map to Go profiler labels
+// and calls pprof.Do.
+//
+// Do is going to do nothing if your Go version is below 1.9.
+func Do(ctx context.Context, f func(ctx context.Context)) {
+	do(ctx, f)
+}
+
+type mutator struct {
+	fn func(t *Map) (*Map, error)
+}
+
+func (m *mutator) Mutate(t *Map) (*Map, error) {
+	return m.fn(t)
+}

vendor/go.opencensus.io/tag/map_codec.go

@@ -0,0 +1,239 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package tag
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// KeyType defines the types of keys allowed. Currently only keyTypeString is
+// supported.
+type keyType byte
+
+const (
+	keyTypeString keyType = iota
+	keyTypeInt64
+	keyTypeTrue
+	keyTypeFalse
+
+	tagsVersionID = byte(0)
+)
+
+type encoderGRPC struct {
+	buf               []byte
+	writeIdx, readIdx int
+}
+
+// writeKeyString writes the fieldID '0' followed by the key string and value
+// string.
+func (eg *encoderGRPC) writeTagString(k, v string) {
+	eg.writeByte(byte(keyTypeString))
+	eg.writeStringWithVarintLen(k)
+	eg.writeStringWithVarintLen(v)
+}
+
+func (eg *encoderGRPC) writeTagUint64(k string, i uint64) {
+	eg.writeByte(byte(keyTypeInt64))
+	eg.writeStringWithVarintLen(k)
+	eg.writeUint64(i)
+}
+
+func (eg *encoderGRPC) writeTagTrue(k string) {
+	eg.writeByte(byte(keyTypeTrue))
+	eg.writeStringWithVarintLen(k)
+}
+
+func (eg *encoderGRPC) writeTagFalse(k string) {
+	eg.writeByte(byte(keyTypeFalse))
+	eg.writeStringWithVarintLen(k)
+}
+
+func (eg *encoderGRPC) writeBytesWithVarintLen(bytes []byte) {
+	length := len(bytes)
+
+	eg.growIfRequired(binary.MaxVarintLen64 + length)
+	eg.writeIdx += binary.PutUvarint(eg.buf[eg.writeIdx:], uint64(length))
+	copy(eg.buf[eg.writeIdx:], bytes)
+	eg.writeIdx += length
+}
+
+func (eg *encoderGRPC) writeStringWithVarintLen(s string) {
+	length := len(s)
+
+	eg.growIfRequired(binary.MaxVarintLen64 + length)
+	eg.writeIdx += binary.PutUvarint(eg.buf[eg.writeIdx:], uint64(length))
+	copy(eg.buf[eg.writeIdx:], s)
+	eg.writeIdx += length
+}
+
+func (eg *encoderGRPC) writeByte(v byte) {
+	eg.growIfRequired(1)
+	eg.buf[eg.writeIdx] = v
+	eg.writeIdx++
+}
+
+func (eg *encoderGRPC) writeUint32(i uint32) {
+	eg.growIfRequired(4)
+	binary.LittleEndian.PutUint32(eg.buf[eg.writeIdx:], i)
+	eg.writeIdx += 4
+}
+
+func (eg *encoderGRPC) writeUint64(i uint64) {
+	eg.growIfRequired(8)
+	binary.LittleEndian.PutUint64(eg.buf[eg.writeIdx:], i)
+	eg.writeIdx += 8
+}
+
+func (eg *encoderGRPC) readByte() byte {
+	b := eg.buf[eg.readIdx]
+	eg.readIdx++
+	return b
+}
+
+func (eg *encoderGRPC) readUint32() uint32 {
+	i := binary.LittleEndian.Uint32(eg.buf[eg.readIdx:])
+	eg.readIdx += 4
+	return i
+}
+
+func (eg *encoderGRPC) readUint64() uint64 {
+	i := binary.LittleEndian.Uint64(eg.buf[eg.readIdx:])
+	eg.readIdx += 8
+	return i
+}
+
+func (eg *encoderGRPC) readBytesWithVarintLen() ([]byte, error) {
+	if eg.readEnded() {
+		return nil, fmt.Errorf("unexpected end while readBytesWithVarintLen '%x' starting at idx '%v'", eg.buf, eg.readIdx)
+	}
+	length, valueStart := binary.Uvarint(eg.buf[eg.readIdx:])
+	if valueStart <= 0 {
+		return nil, fmt.Errorf("unexpected end while readBytesWithVarintLen '%x' starting at idx '%v'", eg.buf, eg.readIdx)
+	}
+
+	valueStart += eg.readIdx
+	valueEnd := valueStart + int(length)
+	if valueEnd > len(eg.buf) {
+		return nil, fmt.Errorf("malformed encoding: length:%v, upper:%v, maxLength:%v", length, valueEnd, len(eg.buf))
+	}
+
+	eg.readIdx = valueEnd
+	return eg.buf[valueStart:valueEnd], nil
+}
+
+func (eg *encoderGRPC) readStringWithVarintLen() (string, error) {
+	bytes, err := eg.readBytesWithVarintLen()
+	if err != nil {
+		return "", err
+	}
+	return string(bytes), nil
+}
+
+func (eg *encoderGRPC) growIfRequired(expected int) {
+	if len(eg.buf)-eg.writeIdx < expected {
+		tmp := make([]byte, 2*(len(eg.buf)+1)+expected)
+		copy(tmp, eg.buf)
+		eg.buf = tmp
+	}
+}
+
+func (eg *encoderGRPC) readEnded() bool {
+	return eg.readIdx >= len(eg.buf)
+}
+
+func (eg *encoderGRPC) bytes() []byte {
+	return eg.buf[:eg.writeIdx]
+}
+
+// Encode encodes the tag map into a []byte. It is useful to propagate
+// the tag maps on wire in binary format.
+func Encode(m *Map) []byte {
+	if m == nil {
+		return nil
+	}
+	eg := &encoderGRPC{
+		buf: make([]byte, len(m.m)),
+	}
+	eg.writeByte(tagsVersionID)
+	for k, v := range m.m {
+		if v.m.ttl.ttl == valueTTLUnlimitedPropagation {
+			eg.writeByte(byte(keyTypeString))
+			eg.writeStringWithVarintLen(k.name)
+			eg.writeBytesWithVarintLen([]byte(v.value))
+		}
+	}
+	return eg.bytes()
+}
+
+// Decode decodes the given []byte into a tag map.
+func Decode(bytes []byte) (*Map, error) {
+	ts := newMap()
+	err := DecodeEach(bytes, ts.upsert)
+	if err != nil {
+		// no partial failures
+		return nil, err
+	}
+	return ts, nil
+}
+
+// DecodeEach decodes the given serialized tag map, calling handler for each
+// tag key and value decoded.
+func DecodeEach(bytes []byte, fn func(key Key, val string, md metadatas)) error {
+	eg := &encoderGRPC{
+		buf: bytes,
+	}
+	if len(eg.buf) == 0 {
+		return nil
+	}
+
+	version := eg.readByte()
+	if version > tagsVersionID {
+		return fmt.Errorf("cannot decode: unsupported version: %q; supports only up to: %q", version, tagsVersionID)
+	}
+
+	for !eg.readEnded() {
+		typ := keyType(eg.readByte())
+
+		if typ != keyTypeString {
+			return fmt.Errorf("cannot decode: invalid key type: %q", typ)
+		}
+
+		k, err := eg.readBytesWithVarintLen()
+		if err != nil {
+			return err
+		}
+
+		v, err := eg.readBytesWithVarintLen()
+		if err != nil {
+			return err
+		}
+
+		key, err := NewKey(string(k))
+		if err != nil {
+			return err
+		}
+		val := string(v)
+		if !checkValue(val) {
+			return errInvalidValue
+		}
+		fn(key, val, createMetadatas(WithTTL(TTLUnlimitedPropagation)))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

vendor/go.opencensus.io/tag/metadata.go

@@ -0,0 +1,52 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package tag
+
+const (
+	// valueTTLNoPropagation prevents tag from propagating.
+	valueTTLNoPropagation = 0
+
+	// valueTTLUnlimitedPropagation allows tag to propagate without any limits on number of hops.
+	valueTTLUnlimitedPropagation = -1
+)
+
+// TTL is metadata that specifies number of hops a tag can propagate.
+// Details about TTL metadata is specified at https://github.com/census-instrumentation/opencensus-specs/blob/master/tags/TagMap.md#tagmetadata
+type TTL struct {
+	ttl int
+}
+
+var (
+	// TTLUnlimitedPropagation is TTL metadata that allows tag to propagate without any limits on number of hops.
+	TTLUnlimitedPropagation = TTL{ttl: valueTTLUnlimitedPropagation}
+
+	// TTLNoPropagation is TTL metadata that prevents tag from propagating.
+	TTLNoPropagation = TTL{ttl: valueTTLNoPropagation}
+)
+
+type metadatas struct {
+	ttl TTL
+}
+
+// Metadata applies metadatas specified by the function.
+type Metadata func(*metadatas)
+
+// WithTTL applies metadata with provided ttl.
+func WithTTL(ttl TTL) Metadata {
+	return func(m *metadatas) {
+		m.ttl = ttl
+	}
+}

vendor/go.opencensus.io/tag/profile_19.go

@@ -0,0 +1,31 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.9
+
+package tag
+
+import (
+	"context"
+	"runtime/pprof"
+)
+
+func do(ctx context.Context, f func(ctx context.Context)) {
+	m := FromContext(ctx)
+	keyvals := make([]string, 0, 2*len(m.m))
+	for k, v := range m.m {
+		keyvals = append(keyvals, k.Name(), v.value)
+	}
+	pprof.Do(ctx, pprof.Labels(keyvals...), f)
+}

vendor/go.opencensus.io/tag/profile_not19.go

@@ -0,0 +1,23 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !go1.9
+
+package tag
+
+import "context"
+
+func do(ctx context.Context, f func(ctx context.Context)) {
+	f(ctx)
+}

vendor/go.opencensus.io/tag/validate.go

@@ -0,0 +1,56 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tag
+
+import "errors"
+
+const (
+	maxKeyLength = 255
+
+	// valid are restricted to US-ASCII subset (range 0x20 (' ') to 0x7e ('~')).
+	validKeyValueMin = 32
+	validKeyValueMax = 126
+)
+
+var (
+	errInvalidKeyName = errors.New("invalid key name: only ASCII characters accepted; max length must be 255 characters")
+	errInvalidValue   = errors.New("invalid value: only ASCII characters accepted; max length must be 255 characters")
+)
+
+func checkKeyName(name string) bool {
+	if len(name) == 0 {
+		return false
+	}
+	if len(name) > maxKeyLength {
+		return false
+	}
+	return isASCII(name)
+}
+
+func isASCII(s string) bool {
+	for _, c := range s {
+		if (c < validKeyValueMin) || (c > validKeyValueMax) {
+			return false
+		}
+	}
+	return true
+}
+
+func checkValue(v string) bool {
+	if len(v) > maxKeyLength {
+		return false
+	}
+	return isASCII(v)
+}

vendor/go.opencensus.io/trace/basetypes.go

@@ -0,0 +1,119 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"fmt"
+	"time"
+)
+
+type (
+	// TraceID is a 16-byte identifier for a set of spans.
+	TraceID [16]byte
+
+	// SpanID is an 8-byte identifier for a single span.
+	SpanID [8]byte
+)
+
+func (t TraceID) String() string {
+	return fmt.Sprintf("%02x", t[:])
+}
+
+func (s SpanID) String() string {
+	return fmt.Sprintf("%02x", s[:])
+}
+
+// Annotation represents a text annotation with a set of attributes and a timestamp.
+type Annotation struct {
+	Time       time.Time
+	Message    string
+	Attributes map[string]interface{}
+}
+
+// Attribute represents a key-value pair on a span, link or annotation.
+// Construct with one of: BoolAttribute, Int64Attribute, or StringAttribute.
+type Attribute struct {
+	key   string
+	value interface{}
+}
+
+// BoolAttribute returns a bool-valued attribute.
+func BoolAttribute(key string, value bool) Attribute {
+	return Attribute{key: key, value: value}
+}
+
+// Int64Attribute returns an int64-valued attribute.
+func Int64Attribute(key string, value int64) Attribute {
+	return Attribute{key: key, value: value}
+}
+
+// Float64Attribute returns a float64-valued attribute.
+func Float64Attribute(key string, value float64) Attribute {
+	return Attribute{key: key, value: value}
+}
+
+// StringAttribute returns a string-valued attribute.
+func StringAttribute(key string, value string) Attribute {
+	return Attribute{key: key, value: value}
+}
+
+// LinkType specifies the relationship between the span that had the link
+// added, and the linked span.
+type LinkType int32
+
+// LinkType values.
+const (
+	LinkTypeUnspecified LinkType = iota // The relationship of the two spans is unknown.
+	LinkTypeChild                       // The linked span is a child of the current span.
+	LinkTypeParent                      // The linked span is the parent of the current span.
+)
+
+// Link represents a reference from one span to another span.
+type Link struct {
+	TraceID TraceID
+	SpanID  SpanID
+	Type    LinkType
+	// Attributes is a set of attributes on the link.
+	Attributes map[string]interface{}
+}
+
+// MessageEventType specifies the type of message event.
+type MessageEventType int32
+
+// MessageEventType values.
+const (
+	MessageEventTypeUnspecified MessageEventType = iota // Unknown event type.
+	MessageEventTypeSent                                // Indicates a sent RPC message.
+	MessageEventTypeRecv                                // Indicates a received RPC message.
+)
+
+// MessageEvent represents an event describing a message sent or received on the network.
+type MessageEvent struct {
+	Time                 time.Time
+	EventType            MessageEventType
+	MessageID            int64
+	UncompressedByteSize int64
+	CompressedByteSize   int64
+}
+
+// Status is the status of a Span.
+type Status struct {
+	// Code is a status code.  Zero indicates success.
+	//
+	// If Code will be propagated to Google APIs, it ideally should be a value from
+	// https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto .
+	Code    int32
+	Message string
+}

vendor/go.opencensus.io/trace/config.go

@@ -0,0 +1,86 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"sync"
+
+	"go.opencensus.io/trace/internal"
+)
+
+// Config represents the global tracing configuration.
+type Config struct {
+	// DefaultSampler is the default sampler used when creating new spans.
+	DefaultSampler Sampler
+
+	// IDGenerator is for internal use only.
+	IDGenerator internal.IDGenerator
+
+	// MaxAnnotationEventsPerSpan is max number of annotation events per span
+	MaxAnnotationEventsPerSpan int
+
+	// MaxMessageEventsPerSpan is max number of message events per span
+	MaxMessageEventsPerSpan int
+
+	// MaxAnnotationEventsPerSpan is max number of attributes per span
+	MaxAttributesPerSpan int
+
+	// MaxLinksPerSpan is max number of links per span
+	MaxLinksPerSpan int
+}
+
+var configWriteMu sync.Mutex
+
+const (
+	// DefaultMaxAnnotationEventsPerSpan is default max number of annotation events per span
+	DefaultMaxAnnotationEventsPerSpan = 32
+
+	// DefaultMaxMessageEventsPerSpan is default max number of message events per span
+	DefaultMaxMessageEventsPerSpan = 128
+
+	// DefaultMaxAttributesPerSpan is default max number of attributes per span
+	DefaultMaxAttributesPerSpan = 32
+
+	// DefaultMaxLinksPerSpan is default max number of links per span
+	DefaultMaxLinksPerSpan = 32
+)
+
+// ApplyConfig applies changes to the global tracing configuration.
+//
+// Fields not provided in the given config are going to be preserved.
+func ApplyConfig(cfg Config) {
+	configWriteMu.Lock()
+	defer configWriteMu.Unlock()
+	c := *config.Load().(*Config)
+	if cfg.DefaultSampler != nil {
+		c.DefaultSampler = cfg.DefaultSampler
+	}
+	if cfg.IDGenerator != nil {
+		c.IDGenerator = cfg.IDGenerator
+	}
+	if cfg.MaxAnnotationEventsPerSpan > 0 {
+		c.MaxAnnotationEventsPerSpan = cfg.MaxAnnotationEventsPerSpan
+	}
+	if cfg.MaxMessageEventsPerSpan > 0 {
+		c.MaxMessageEventsPerSpan = cfg.MaxMessageEventsPerSpan
+	}
+	if cfg.MaxAttributesPerSpan > 0 {
+		c.MaxAttributesPerSpan = cfg.MaxAttributesPerSpan
+	}
+	if cfg.MaxLinksPerSpan > 0 {
+		c.MaxLinksPerSpan = cfg.MaxLinksPerSpan
+	}
+	config.Store(&c)
+}

vendor/go.opencensus.io/trace/doc.go

@@ -0,0 +1,53 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/*
+Package trace contains support for OpenCensus distributed tracing.
+
+The following assumes a basic familiarity with OpenCensus concepts.
+See http://opencensus.io
+
+
+Exporting Traces
+
+To export collected tracing data, register at least one exporter. You can use
+one of the provided exporters or write your own.
+
+    trace.RegisterExporter(exporter)
+
+By default, traces will be sampled relatively rarely. To change the sampling
+frequency for your entire program, call ApplyConfig. Use a ProbabilitySampler
+to sample a subset of traces, or use AlwaysSample to collect a trace on every run:
+
+    trace.ApplyConfig(trace.Config{DefaultSampler: trace.AlwaysSample()})
+
+Be careful about using trace.AlwaysSample in a production application with
+significant traffic: a new trace will be started and exported for every request.
+
+Adding Spans to a Trace
+
+A trace consists of a tree of spans. In Go, the current span is carried in a
+context.Context.
+
+It is common to want to capture all the activity of a function call in a span. For
+this to work, the function must take a context.Context as a parameter. Add these two
+lines to the top of the function:
+
+    ctx, span := trace.StartSpan(ctx, "example.com/Run")
+    defer span.End()
+
+StartSpan will create a new top-level span if the context
+doesn't contain another span, otherwise it will create a child span.
+*/
+package trace // import "go.opencensus.io/trace"

vendor/go.opencensus.io/trace/evictedqueue.go

@@ -0,0 +1,38 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+type evictedQueue struct {
+	queue        []interface{}
+	capacity     int
+	droppedCount int
+}
+
+func newEvictedQueue(capacity int) *evictedQueue {
+	eq := &evictedQueue{
+		capacity: capacity,
+		queue:    make([]interface{}, 0),
+	}
+
+	return eq
+}
+
+func (eq *evictedQueue) add(value interface{}) {
+	if len(eq.queue) == eq.capacity {
+		eq.queue = eq.queue[1:]
+		eq.droppedCount++
+	}
+	eq.queue = append(eq.queue, value)
+}

vendor/go.opencensus.io/trace/export.go

@@ -0,0 +1,97 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// Exporter is a type for functions that receive sampled trace spans.
+//
+// The ExportSpan method should be safe for concurrent use and should return
+// quickly; if an Exporter takes a significant amount of time to process a
+// SpanData, that work should be done on another goroutine.
+//
+// The SpanData should not be modified, but a pointer to it can be kept.
+type Exporter interface {
+	ExportSpan(s *SpanData)
+}
+
+type exportersMap map[Exporter]struct{}
+
+var (
+	exporterMu sync.Mutex
+	exporters  atomic.Value
+)
+
+// RegisterExporter adds to the list of Exporters that will receive sampled
+// trace spans.
+//
+// Binaries can register exporters, libraries shouldn't register exporters.
+func RegisterExporter(e Exporter) {
+	exporterMu.Lock()
+	new := make(exportersMap)
+	if old, ok := exporters.Load().(exportersMap); ok {
+		for k, v := range old {
+			new[k] = v
+		}
+	}
+	new[e] = struct{}{}
+	exporters.Store(new)
+	exporterMu.Unlock()
+}
+
+// UnregisterExporter removes from the list of Exporters the Exporter that was
+// registered with the given name.
+func UnregisterExporter(e Exporter) {
+	exporterMu.Lock()
+	new := make(exportersMap)
+	if old, ok := exporters.Load().(exportersMap); ok {
+		for k, v := range old {
+			new[k] = v
+		}
+	}
+	delete(new, e)
+	exporters.Store(new)
+	exporterMu.Unlock()
+}
+
+// SpanData contains all the information collected by a Span.
+type SpanData struct {
+	SpanContext
+	ParentSpanID SpanID
+	SpanKind     int
+	Name         string
+	StartTime    time.Time
+	// The wall clock time of EndTime will be adjusted to always be offset
+	// from StartTime by the duration of the span.
+	EndTime time.Time
+	// The values of Attributes each have type string, bool, or int64.
+	Attributes    map[string]interface{}
+	Annotations   []Annotation
+	MessageEvents []MessageEvent
+	Status
+	Links                    []Link
+	HasRemoteParent          bool
+	DroppedAttributeCount    int
+	DroppedAnnotationCount   int
+	DroppedMessageEventCount int
+	DroppedLinkCount         int
+
+	// ChildSpanCount holds the number of child span created for this span.
+	ChildSpanCount int
+}

vendor/go.opencensus.io/trace/internal/internal.go

@@ -0,0 +1,22 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package internal provides trace internals.
+package internal
+
+// IDGenerator allows custom generators for TraceId and SpanId.
+type IDGenerator interface {
+	NewTraceID() [16]byte
+	NewSpanID() [8]byte
+}

vendor/go.opencensus.io/trace/lrumap.go

@@ -0,0 +1,61 @@
+// Copyright 2019, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"github.com/golang/groupcache/lru"
+)
+
+// A simple lru.Cache wrapper that tracks the keys of the current contents and
+// the cumulative number of evicted items.
+type lruMap struct {
+	cacheKeys    map[lru.Key]bool
+	cache        *lru.Cache
+	droppedCount int
+}
+
+func newLruMap(size int) *lruMap {
+	lm := &lruMap{
+		cacheKeys:    make(map[lru.Key]bool),
+		cache:        lru.New(size),
+		droppedCount: 0,
+	}
+	lm.cache.OnEvicted = func(key lru.Key, value interface{}) {
+		delete(lm.cacheKeys, key)
+		lm.droppedCount++
+	}
+	return lm
+}
+
+func (lm lruMap) len() int {
+	return lm.cache.Len()
+}
+
+func (lm lruMap) keys() []interface{} {
+	keys := make([]interface{}, len(lm.cacheKeys))
+	for k := range lm.cacheKeys {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+func (lm *lruMap) add(key, value interface{}) {
+	lm.cacheKeys[lru.Key(key)] = true
+	lm.cache.Add(lru.Key(key), value)
+}
+
+func (lm *lruMap) get(key interface{}) (interface{}, bool) {
+	return lm.cache.Get(key)
+}

vendor/go.opencensus.io/trace/propagation/propagation.go

@@ -0,0 +1,108 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package propagation implements the binary trace context format.
+package propagation // import "go.opencensus.io/trace/propagation"
+
+// TODO: link to external spec document.
+
+// BinaryFormat format:
+//
+// Binary value: <version_id><version_format>
+// version_id: 1 byte representing the version id.
+//
+// For version_id = 0:
+//
+// version_format: <field><field>
+// field_format: <field_id><field_format>
+//
+// Fields:
+//
+// TraceId: (field_id = 0, len = 16, default = "0000000000000000") - 16-byte array representing the trace_id.
+// SpanId: (field_id = 1, len = 8, default = "00000000") - 8-byte array representing the span_id.
+// TraceOptions: (field_id = 2, len = 1, default = "0") - 1-byte array representing the trace_options.
+//
+// Fields MUST be encoded using the field id order (smaller to higher).
+//
+// Valid value example:
+//
+// {0, 0, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 1, 97,
+// 98, 99, 100, 101, 102, 103, 104, 2, 1}
+//
+// version_id = 0;
+// trace_id = {64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79}
+// span_id = {97, 98, 99, 100, 101, 102, 103, 104};
+// trace_options = {1};
+
+import (
+	"net/http"
+
+	"go.opencensus.io/trace"
+)
+
+// Binary returns the binary format representation of a SpanContext.
+//
+// If sc is the zero value, Binary returns nil.
+func Binary(sc trace.SpanContext) []byte {
+	if sc == (trace.SpanContext{}) {
+		return nil
+	}
+	var b [29]byte
+	copy(b[2:18], sc.TraceID[:])
+	b[18] = 1
+	copy(b[19:27], sc.SpanID[:])
+	b[27] = 2
+	b[28] = uint8(sc.TraceOptions)
+	return b[:]
+}
+
+// FromBinary returns the SpanContext represented by b.
+//
+// If b has an unsupported version ID or contains no TraceID, FromBinary
+// returns with ok==false.
+func FromBinary(b []byte) (sc trace.SpanContext, ok bool) {
+	if len(b) == 0 || b[0] != 0 {
+		return trace.SpanContext{}, false
+	}
+	b = b[1:]
+	if len(b) >= 17 && b[0] == 0 {
+		copy(sc.TraceID[:], b[1:17])
+		b = b[17:]
+	} else {
+		return trace.SpanContext{}, false
+	}
+	if len(b) >= 9 && b[0] == 1 {
+		copy(sc.SpanID[:], b[1:9])
+		b = b[9:]
+	}
+	if len(b) >= 2 && b[0] == 2 {
+		sc.TraceOptions = trace.TraceOptions(b[1])
+	}
+	return sc, true
+}
+
+// HTTPFormat implementations propagate span contexts
+// in HTTP requests.
+//
+// SpanContextFromRequest extracts a span context from incoming
+// requests.
+//
+// SpanContextToRequest modifies the given request to include the given
+// span context.
+type HTTPFormat interface {
+	SpanContextFromRequest(req *http.Request) (sc trace.SpanContext, ok bool)
+	SpanContextToRequest(sc trace.SpanContext, req *http.Request)
+}
+
+// TODO(jbd): Find a more representative but short name for HTTPFormat.

vendor/go.opencensus.io/trace/sampling.go

@@ -0,0 +1,75 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"encoding/binary"
+)
+
+const defaultSamplingProbability = 1e-4
+
+// Sampler decides whether a trace should be sampled and exported.
+type Sampler func(SamplingParameters) SamplingDecision
+
+// SamplingParameters contains the values passed to a Sampler.
+type SamplingParameters struct {
+	ParentContext   SpanContext
+	TraceID         TraceID
+	SpanID          SpanID
+	Name            string
+	HasRemoteParent bool
+}
+
+// SamplingDecision is the value returned by a Sampler.
+type SamplingDecision struct {
+	Sample bool
+}
+
+// ProbabilitySampler returns a Sampler that samples a given fraction of traces.
+//
+// It also samples spans whose parents are sampled.
+func ProbabilitySampler(fraction float64) Sampler {
+	if !(fraction >= 0) {
+		fraction = 0
+	} else if fraction >= 1 {
+		return AlwaysSample()
+	}
+
+	traceIDUpperBound := uint64(fraction * (1 << 63))
+	return Sampler(func(p SamplingParameters) SamplingDecision {
+		if p.ParentContext.IsSampled() {
+			return SamplingDecision{Sample: true}
+		}
+		x := binary.BigEndian.Uint64(p.TraceID[0:8]) >> 1
+		return SamplingDecision{Sample: x < traceIDUpperBound}
+	})
+}
+
+// AlwaysSample returns a Sampler that samples every trace.
+// Be careful about using this sampler in a production application with
+// significant traffic: a new trace will be started and exported for every
+// request.
+func AlwaysSample() Sampler {
+	return func(p SamplingParameters) SamplingDecision {
+		return SamplingDecision{Sample: true}
+	}
+}
+
+// NeverSample returns a Sampler that samples no traces.
+func NeverSample() Sampler {
+	return func(p SamplingParameters) SamplingDecision {
+		return SamplingDecision{Sample: false}
+	}
+}

vendor/go.opencensus.io/trace/spanbucket.go

@@ -0,0 +1,130 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"time"
+)
+
+// samplePeriod is the minimum time between accepting spans in a single bucket.
+const samplePeriod = time.Second
+
+// defaultLatencies contains the default latency bucket bounds.
+// TODO: consider defaults, make configurable
+var defaultLatencies = [...]time.Duration{
+	10 * time.Microsecond,
+	100 * time.Microsecond,
+	time.Millisecond,
+	10 * time.Millisecond,
+	100 * time.Millisecond,
+	time.Second,
+	10 * time.Second,
+	time.Minute,
+}
+
+// bucket is a container for a set of spans for a particular error code or latency range.
+type bucket struct {
+	nextTime  time.Time   // next time we can accept a span
+	buffer    []*SpanData // circular buffer of spans
+	nextIndex int         // location next SpanData should be placed in buffer
+	overflow  bool        // whether the circular buffer has wrapped around
+}
+
+func makeBucket(bufferSize int) bucket {
+	return bucket{
+		buffer: make([]*SpanData, bufferSize),
+	}
+}
+
+// add adds a span to the bucket, if nextTime has been reached.
+func (b *bucket) add(s *SpanData) {
+	if s.EndTime.Before(b.nextTime) {
+		return
+	}
+	if len(b.buffer) == 0 {
+		return
+	}
+	b.nextTime = s.EndTime.Add(samplePeriod)
+	b.buffer[b.nextIndex] = s
+	b.nextIndex++
+	if b.nextIndex == len(b.buffer) {
+		b.nextIndex = 0
+		b.overflow = true
+	}
+}
+
+// size returns the number of spans in the bucket.
+func (b *bucket) size() int {
+	if b.overflow {
+		return len(b.buffer)
+	}
+	return b.nextIndex
+}
+
+// span returns the ith span in the bucket.
+func (b *bucket) span(i int) *SpanData {
+	if !b.overflow {
+		return b.buffer[i]
+	}
+	if i < len(b.buffer)-b.nextIndex {
+		return b.buffer[b.nextIndex+i]
+	}
+	return b.buffer[b.nextIndex+i-len(b.buffer)]
+}
+
+// resize changes the size of the bucket to n, keeping up to n existing spans.
+func (b *bucket) resize(n int) {
+	cur := b.size()
+	newBuffer := make([]*SpanData, n)
+	if cur < n {
+		for i := 0; i < cur; i++ {
+			newBuffer[i] = b.span(i)
+		}
+		b.buffer = newBuffer
+		b.nextIndex = cur
+		b.overflow = false
+		return
+	}
+	for i := 0; i < n; i++ {
+		newBuffer[i] = b.span(i + cur - n)
+	}
+	b.buffer = newBuffer
+	b.nextIndex = 0
+	b.overflow = true
+}
+
+// latencyBucket returns the appropriate bucket number for a given latency.
+func latencyBucket(latency time.Duration) int {
+	i := 0
+	for i < len(defaultLatencies) && latency >= defaultLatencies[i] {
+		i++
+	}
+	return i
+}
+
+// latencyBucketBounds returns the lower and upper bounds for a latency bucket
+// number.
+//
+// The lower bound is inclusive, the upper bound is exclusive (except for the
+// last bucket.)
+func latencyBucketBounds(index int) (lower time.Duration, upper time.Duration) {
+	if index == 0 {
+		return 0, defaultLatencies[index]
+	}
+	if index == len(defaultLatencies) {
+		return defaultLatencies[index-1], 1<<63 - 1
+	}
+	return defaultLatencies[index-1], defaultLatencies[index]
+}

vendor/go.opencensus.io/trace/spanstore.go

@@ -0,0 +1,306 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"sync"
+	"time"
+
+	"go.opencensus.io/internal"
+)
+
+const (
+	maxBucketSize     = 100000
+	defaultBucketSize = 10
+)
+
+var (
+	ssmu       sync.RWMutex // protects spanStores
+	spanStores = make(map[string]*spanStore)
+)
+
+// This exists purely to avoid exposing internal methods used by z-Pages externally.
+type internalOnly struct{}
+
+func init() {
+	//TODO(#412): remove
+	internal.Trace = &internalOnly{}
+}
+
+// ReportActiveSpans returns the active spans for the given name.
+func (i internalOnly) ReportActiveSpans(name string) []*SpanData {
+	s := spanStoreForName(name)
+	if s == nil {
+		return nil
+	}
+	var out []*SpanData
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for span := range s.active {
+		out = append(out, span.makeSpanData())
+	}
+	return out
+}
+
+// ReportSpansByError returns a sample of error spans.
+//
+// If code is nonzero, only spans with that status code are returned.
+func (i internalOnly) ReportSpansByError(name string, code int32) []*SpanData {
+	s := spanStoreForName(name)
+	if s == nil {
+		return nil
+	}
+	var out []*SpanData
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if code != 0 {
+		if b, ok := s.errors[code]; ok {
+			for _, sd := range b.buffer {
+				if sd == nil {
+					break
+				}
+				out = append(out, sd)
+			}
+		}
+	} else {
+		for _, b := range s.errors {
+			for _, sd := range b.buffer {
+				if sd == nil {
+					break
+				}
+				out = append(out, sd)
+			}
+		}
+	}
+	return out
+}
+
+// ConfigureBucketSizes sets the number of spans to keep per latency and error
+// bucket for different span names.
+func (i internalOnly) ConfigureBucketSizes(bcs []internal.BucketConfiguration) {
+	for _, bc := range bcs {
+		latencyBucketSize := bc.MaxRequestsSucceeded
+		if latencyBucketSize < 0 {
+			latencyBucketSize = 0
+		}
+		if latencyBucketSize > maxBucketSize {
+			latencyBucketSize = maxBucketSize
+		}
+		errorBucketSize := bc.MaxRequestsErrors
+		if errorBucketSize < 0 {
+			errorBucketSize = 0
+		}
+		if errorBucketSize > maxBucketSize {
+			errorBucketSize = maxBucketSize
+		}
+		spanStoreSetSize(bc.Name, latencyBucketSize, errorBucketSize)
+	}
+}
+
+// ReportSpansPerMethod returns a summary of what spans are being stored for each span name.
+func (i internalOnly) ReportSpansPerMethod() map[string]internal.PerMethodSummary {
+	out := make(map[string]internal.PerMethodSummary)
+	ssmu.RLock()
+	defer ssmu.RUnlock()
+	for name, s := range spanStores {
+		s.mu.Lock()
+		p := internal.PerMethodSummary{
+			Active: len(s.active),
+		}
+		for code, b := range s.errors {
+			p.ErrorBuckets = append(p.ErrorBuckets, internal.ErrorBucketSummary{
+				ErrorCode: code,
+				Size:      b.size(),
+			})
+		}
+		for i, b := range s.latency {
+			min, max := latencyBucketBounds(i)
+			p.LatencyBuckets = append(p.LatencyBuckets, internal.LatencyBucketSummary{
+				MinLatency: min,
+				MaxLatency: max,
+				Size:       b.size(),
+			})
+		}
+		s.mu.Unlock()
+		out[name] = p
+	}
+	return out
+}
+
+// ReportSpansByLatency returns a sample of successful spans.
+//
+// minLatency is the minimum latency of spans to be returned.
+// maxLatency, if nonzero, is the maximum latency of spans to be returned.
+func (i internalOnly) ReportSpansByLatency(name string, minLatency, maxLatency time.Duration) []*SpanData {
+	s := spanStoreForName(name)
+	if s == nil {
+		return nil
+	}
+	var out []*SpanData
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for i, b := range s.latency {
+		min, max := latencyBucketBounds(i)
+		if i+1 != len(s.latency) && max <= minLatency {
+			continue
+		}
+		if maxLatency != 0 && maxLatency < min {
+			continue
+		}
+		for _, sd := range b.buffer {
+			if sd == nil {
+				break
+			}
+			if minLatency != 0 || maxLatency != 0 {
+				d := sd.EndTime.Sub(sd.StartTime)
+				if d < minLatency {
+					continue
+				}
+				if maxLatency != 0 && d > maxLatency {
+					continue
+				}
+			}
+			out = append(out, sd)
+		}
+	}
+	return out
+}
+
+// spanStore keeps track of spans stored for a particular span name.
+//
+// It contains all active spans; a sample of spans for failed requests,
+// categorized by error code; and a sample of spans for successful requests,
+// bucketed by latency.
+type spanStore struct {
+	mu                     sync.Mutex // protects everything below.
+	active                 map[*Span]struct{}
+	errors                 map[int32]*bucket
+	latency                []bucket
+	maxSpansPerErrorBucket int
+}
+
+// newSpanStore creates a span store.
+func newSpanStore(name string, latencyBucketSize int, errorBucketSize int) *spanStore {
+	s := &spanStore{
+		active:                 make(map[*Span]struct{}),
+		latency:                make([]bucket, len(defaultLatencies)+1),
+		maxSpansPerErrorBucket: errorBucketSize,
+	}
+	for i := range s.latency {
+		s.latency[i] = makeBucket(latencyBucketSize)
+	}
+	return s
+}
+
+// spanStoreForName returns the spanStore for the given name.
+//
+// It returns nil if it doesn't exist.
+func spanStoreForName(name string) *spanStore {
+	var s *spanStore
+	ssmu.RLock()
+	s, _ = spanStores[name]
+	ssmu.RUnlock()
+	return s
+}
+
+// spanStoreForNameCreateIfNew returns the spanStore for the given name.
+//
+// It creates it if it didn't exist.
+func spanStoreForNameCreateIfNew(name string) *spanStore {
+	ssmu.RLock()
+	s, ok := spanStores[name]
+	ssmu.RUnlock()
+	if ok {
+		return s
+	}
+	ssmu.Lock()
+	defer ssmu.Unlock()
+	s, ok = spanStores[name]
+	if ok {
+		return s
+	}
+	s = newSpanStore(name, defaultBucketSize, defaultBucketSize)
+	spanStores[name] = s
+	return s
+}
+
+// spanStoreSetSize resizes the spanStore for the given name.
+//
+// It creates it if it didn't exist.
+func spanStoreSetSize(name string, latencyBucketSize int, errorBucketSize int) {
+	ssmu.RLock()
+	s, ok := spanStores[name]
+	ssmu.RUnlock()
+	if ok {
+		s.resize(latencyBucketSize, errorBucketSize)
+		return
+	}
+	ssmu.Lock()
+	defer ssmu.Unlock()
+	s, ok = spanStores[name]
+	if ok {
+		s.resize(latencyBucketSize, errorBucketSize)
+		return
+	}
+	s = newSpanStore(name, latencyBucketSize, errorBucketSize)
+	spanStores[name] = s
+}
+
+func (s *spanStore) resize(latencyBucketSize int, errorBucketSize int) {
+	s.mu.Lock()
+	for i := range s.latency {
+		s.latency[i].resize(latencyBucketSize)
+	}
+	for _, b := range s.errors {
+		b.resize(errorBucketSize)
+	}
+	s.maxSpansPerErrorBucket = errorBucketSize
+	s.mu.Unlock()
+}
+
+// add adds a span to the active bucket of the spanStore.
+func (s *spanStore) add(span *Span) {
+	s.mu.Lock()
+	s.active[span] = struct{}{}
+	s.mu.Unlock()
+}
+
+// finished removes a span from the active set, and adds a corresponding
+// SpanData to a latency or error bucket.
+func (s *spanStore) finished(span *Span, sd *SpanData) {
+	latency := sd.EndTime.Sub(sd.StartTime)
+	if latency < 0 {
+		latency = 0
+	}
+	code := sd.Status.Code
+
+	s.mu.Lock()
+	delete(s.active, span)
+	if code == 0 {
+		s.latency[latencyBucket(latency)].add(sd)
+	} else {
+		if s.errors == nil {
+			s.errors = make(map[int32]*bucket)
+		}
+		if b := s.errors[code]; b != nil {
+			b.add(sd)
+		} else {
+			b := makeBucket(s.maxSpansPerErrorBucket)
+			s.errors[code] = &b
+			b.add(sd)
+		}
+	}
+	s.mu.Unlock()
+}

vendor/go.opencensus.io/trace/status_codes.go

@@ -0,0 +1,37 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+// Status codes for use with Span.SetStatus. These correspond to the status
+// codes used by gRPC defined here: https://github.com/googleapis/googleapis/blob/master/google/rpc/code.proto
+const (
+	StatusCodeOK                 = 0
+	StatusCodeCancelled          = 1
+	StatusCodeUnknown            = 2
+	StatusCodeInvalidArgument    = 3
+	StatusCodeDeadlineExceeded   = 4
+	StatusCodeNotFound           = 5
+	StatusCodeAlreadyExists      = 6
+	StatusCodePermissionDenied   = 7
+	StatusCodeResourceExhausted  = 8
+	StatusCodeFailedPrecondition = 9
+	StatusCodeAborted            = 10
+	StatusCodeOutOfRange         = 11
+	StatusCodeUnimplemented      = 12
+	StatusCodeInternal           = 13
+	StatusCodeUnavailable        = 14
+	StatusCodeDataLoss           = 15
+	StatusCodeUnauthenticated    = 16
+)

vendor/go.opencensus.io/trace/trace.go

@@ -0,0 +1,598 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace
+
+import (
+	"context"
+	crand "crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"go.opencensus.io/internal"
+	"go.opencensus.io/trace/tracestate"
+)
+
+// Span represents a span of a trace.  It has an associated SpanContext, and
+// stores data accumulated while the span is active.
+//
+// Ideally users should interact with Spans by calling the functions in this
+// package that take a Context parameter.
+type Span struct {
+	// data contains information recorded about the span.
+	//
+	// It will be non-nil if we are exporting the span or recording events for it.
+	// Otherwise, data is nil, and the Span is simply a carrier for the
+	// SpanContext, so that the trace ID is propagated.
+	data        *SpanData
+	mu          sync.Mutex // protects the contents of *data (but not the pointer value.)
+	spanContext SpanContext
+
+	// lruAttributes are capped at configured limit. When the capacity is reached an oldest entry
+	// is removed to create room for a new entry.
+	lruAttributes *lruMap
+
+	// annotations are stored in FIFO queue capped by configured limit.
+	annotations *evictedQueue
+
+	// messageEvents are stored in FIFO queue capped by configured limit.
+	messageEvents *evictedQueue
+
+	// links are stored in FIFO queue capped by configured limit.
+	links *evictedQueue
+
+	// spanStore is the spanStore this span belongs to, if any, otherwise it is nil.
+	*spanStore
+	endOnce sync.Once
+
+	executionTracerTaskEnd func() // ends the execution tracer span
+}
+
+// IsRecordingEvents returns true if events are being recorded for this span.
+// Use this check to avoid computing expensive annotations when they will never
+// be used.
+func (s *Span) IsRecordingEvents() bool {
+	if s == nil {
+		return false
+	}
+	return s.data != nil
+}
+
+// TraceOptions contains options associated with a trace span.
+type TraceOptions uint32
+
+// IsSampled returns true if the span will be exported.
+func (sc SpanContext) IsSampled() bool {
+	return sc.TraceOptions.IsSampled()
+}
+
+// setIsSampled sets the TraceOptions bit that determines whether the span will be exported.
+func (sc *SpanContext) setIsSampled(sampled bool) {
+	if sampled {
+		sc.TraceOptions |= 1
+	} else {
+		sc.TraceOptions &= ^TraceOptions(1)
+	}
+}
+
+// IsSampled returns true if the span will be exported.
+func (t TraceOptions) IsSampled() bool {
+	return t&1 == 1
+}
+
+// SpanContext contains the state that must propagate across process boundaries.
+//
+// SpanContext is not an implementation of context.Context.
+// TODO: add reference to external Census docs for SpanContext.
+type SpanContext struct {
+	TraceID      TraceID
+	SpanID       SpanID
+	TraceOptions TraceOptions
+	Tracestate   *tracestate.Tracestate
+}
+
+type contextKey struct{}
+
+// FromContext returns the Span stored in a context, or nil if there isn't one.
+func FromContext(ctx context.Context) *Span {
+	s, _ := ctx.Value(contextKey{}).(*Span)
+	return s
+}
+
+// NewContext returns a new context with the given Span attached.
+func NewContext(parent context.Context, s *Span) context.Context {
+	return context.WithValue(parent, contextKey{}, s)
+}
+
+// All available span kinds. Span kind must be either one of these values.
+const (
+	SpanKindUnspecified = iota
+	SpanKindServer
+	SpanKindClient
+)
+
+// StartOptions contains options concerning how a span is started.
+type StartOptions struct {
+	// Sampler to consult for this Span. If provided, it is always consulted.
+	//
+	// If not provided, then the behavior differs based on whether
+	// the parent of this Span is remote, local, or there is no parent.
+	// In the case of a remote parent or no parent, the
+	// default sampler (see Config) will be consulted. Otherwise,
+	// when there is a non-remote parent, no new sampling decision will be made:
+	// we will preserve the sampling of the parent.
+	Sampler Sampler
+
+	// SpanKind represents the kind of a span. If none is set,
+	// SpanKindUnspecified is used.
+	SpanKind int
+}
+
+// StartOption apply changes to StartOptions.
+type StartOption func(*StartOptions)
+
+// WithSpanKind makes new spans to be created with the given kind.
+func WithSpanKind(spanKind int) StartOption {
+	return func(o *StartOptions) {
+		o.SpanKind = spanKind
+	}
+}
+
+// WithSampler makes new spans to be be created with a custom sampler.
+// Otherwise, the global sampler is used.
+func WithSampler(sampler Sampler) StartOption {
+	return func(o *StartOptions) {
+		o.Sampler = sampler
+	}
+}
+
+// StartSpan starts a new child span of the current span in the context. If
+// there is no span in the context, creates a new trace and span.
+//
+// Returned context contains the newly created span. You can use it to
+// propagate the returned span in process.
+func StartSpan(ctx context.Context, name string, o ...StartOption) (context.Context, *Span) {
+	var opts StartOptions
+	var parent SpanContext
+	if p := FromContext(ctx); p != nil {
+		p.addChild()
+		parent = p.spanContext
+	}
+	for _, op := range o {
+		op(&opts)
+	}
+	span := startSpanInternal(name, parent != SpanContext{}, parent, false, opts)
+
+	ctx, end := startExecutionTracerTask(ctx, name)
+	span.executionTracerTaskEnd = end
+	return NewContext(ctx, span), span
+}
+
+// StartSpanWithRemoteParent starts a new child span of the span from the given parent.
+//
+// If the incoming context contains a parent, it ignores. StartSpanWithRemoteParent is
+// preferred for cases where the parent is propagated via an incoming request.
+//
+// Returned context contains the newly created span. You can use it to
+// propagate the returned span in process.
+func StartSpanWithRemoteParent(ctx context.Context, name string, parent SpanContext, o ...StartOption) (context.Context, *Span) {
+	var opts StartOptions
+	for _, op := range o {
+		op(&opts)
+	}
+	span := startSpanInternal(name, parent != SpanContext{}, parent, true, opts)
+	ctx, end := startExecutionTracerTask(ctx, name)
+	span.executionTracerTaskEnd = end
+	return NewContext(ctx, span), span
+}
+
+func startSpanInternal(name string, hasParent bool, parent SpanContext, remoteParent bool, o StartOptions) *Span {
+	span := &Span{}
+	span.spanContext = parent
+
+	cfg := config.Load().(*Config)
+
+	if !hasParent {
+		span.spanContext.TraceID = cfg.IDGenerator.NewTraceID()
+	}
+	span.spanContext.SpanID = cfg.IDGenerator.NewSpanID()
+	sampler := cfg.DefaultSampler
+
+	if !hasParent || remoteParent || o.Sampler != nil {
+		// If this span is the child of a local span and no Sampler is set in the
+		// options, keep the parent's TraceOptions.
+		//
+		// Otherwise, consult the Sampler in the options if it is non-nil, otherwise
+		// the default sampler.
+		if o.Sampler != nil {
+			sampler = o.Sampler
+		}
+		span.spanContext.setIsSampled(sampler(SamplingParameters{
+			ParentContext:   parent,
+			TraceID:         span.spanContext.TraceID,
+			SpanID:          span.spanContext.SpanID,
+			Name:            name,
+			HasRemoteParent: remoteParent}).Sample)
+	}
+
+	if !internal.LocalSpanStoreEnabled && !span.spanContext.IsSampled() {
+		return span
+	}
+
+	span.data = &SpanData{
+		SpanContext:     span.spanContext,
+		StartTime:       time.Now(),
+		SpanKind:        o.SpanKind,
+		Name:            name,
+		HasRemoteParent: remoteParent,
+	}
+	span.lruAttributes = newLruMap(cfg.MaxAttributesPerSpan)
+	span.annotations = newEvictedQueue(cfg.MaxAnnotationEventsPerSpan)
+	span.messageEvents = newEvictedQueue(cfg.MaxMessageEventsPerSpan)
+	span.links = newEvictedQueue(cfg.MaxLinksPerSpan)
+
+	if hasParent {
+		span.data.ParentSpanID = parent.SpanID
+	}
+	if internal.LocalSpanStoreEnabled {
+		var ss *spanStore
+		ss = spanStoreForNameCreateIfNew(name)
+		if ss != nil {
+			span.spanStore = ss
+			ss.add(span)
+		}
+	}
+
+	return span
+}
+
+// End ends the span.
+func (s *Span) End() {
+	if s == nil {
+		return
+	}
+	if s.executionTracerTaskEnd != nil {
+		s.executionTracerTaskEnd()
+	}
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.endOnce.Do(func() {
+		exp, _ := exporters.Load().(exportersMap)
+		mustExport := s.spanContext.IsSampled() && len(exp) > 0
+		if s.spanStore != nil || mustExport {
+			sd := s.makeSpanData()
+			sd.EndTime = internal.MonotonicEndTime(sd.StartTime)
+			if s.spanStore != nil {
+				s.spanStore.finished(s, sd)
+			}
+			if mustExport {
+				for e := range exp {
+					e.ExportSpan(sd)
+				}
+			}
+		}
+	})
+}
+
+// makeSpanData produces a SpanData representing the current state of the Span.
+// It requires that s.data is non-nil.
+func (s *Span) makeSpanData() *SpanData {
+	var sd SpanData
+	s.mu.Lock()
+	sd = *s.data
+	if s.lruAttributes.len() > 0 {
+		sd.Attributes = s.lruAttributesToAttributeMap()
+		sd.DroppedAttributeCount = s.lruAttributes.droppedCount
+	}
+	if len(s.annotations.queue) > 0 {
+		sd.Annotations = s.interfaceArrayToAnnotationArray()
+		sd.DroppedAnnotationCount = s.annotations.droppedCount
+	}
+	if len(s.messageEvents.queue) > 0 {
+		sd.MessageEvents = s.interfaceArrayToMessageEventArray()
+		sd.DroppedMessageEventCount = s.messageEvents.droppedCount
+	}
+	if len(s.links.queue) > 0 {
+		sd.Links = s.interfaceArrayToLinksArray()
+		sd.DroppedLinkCount = s.links.droppedCount
+	}
+	s.mu.Unlock()
+	return &sd
+}
+
+// SpanContext returns the SpanContext of the span.
+func (s *Span) SpanContext() SpanContext {
+	if s == nil {
+		return SpanContext{}
+	}
+	return s.spanContext
+}
+
+// SetName sets the name of the span, if it is recording events.
+func (s *Span) SetName(name string) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.Name = name
+	s.mu.Unlock()
+}
+
+// SetStatus sets the status of the span, if it is recording events.
+func (s *Span) SetStatus(status Status) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.Status = status
+	s.mu.Unlock()
+}
+
+func (s *Span) interfaceArrayToLinksArray() []Link {
+	linksArr := make([]Link, 0, len(s.links.queue))
+	for _, value := range s.links.queue {
+		linksArr = append(linksArr, value.(Link))
+	}
+	return linksArr
+}
+
+func (s *Span) interfaceArrayToMessageEventArray() []MessageEvent {
+	messageEventArr := make([]MessageEvent, 0, len(s.messageEvents.queue))
+	for _, value := range s.messageEvents.queue {
+		messageEventArr = append(messageEventArr, value.(MessageEvent))
+	}
+	return messageEventArr
+}
+
+func (s *Span) interfaceArrayToAnnotationArray() []Annotation {
+	annotationArr := make([]Annotation, 0, len(s.annotations.queue))
+	for _, value := range s.annotations.queue {
+		annotationArr = append(annotationArr, value.(Annotation))
+	}
+	return annotationArr
+}
+
+func (s *Span) lruAttributesToAttributeMap() map[string]interface{} {
+	attributes := make(map[string]interface{}, s.lruAttributes.len())
+	for _, key := range s.lruAttributes.keys() {
+		value, ok := s.lruAttributes.get(key)
+		if ok {
+			keyStr := key.(string)
+			attributes[keyStr] = value
+		}
+	}
+	return attributes
+}
+
+func (s *Span) copyToCappedAttributes(attributes []Attribute) {
+	for _, a := range attributes {
+		s.lruAttributes.add(a.key, a.value)
+	}
+}
+
+func (s *Span) addChild() {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.data.ChildSpanCount++
+	s.mu.Unlock()
+}
+
+// AddAttributes sets attributes in the span.
+//
+// Existing attributes whose keys appear in the attributes parameter are overwritten.
+func (s *Span) AddAttributes(attributes ...Attribute) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.copyToCappedAttributes(attributes)
+	s.mu.Unlock()
+}
+
+// copyAttributes copies a slice of Attributes into a map.
+func copyAttributes(m map[string]interface{}, attributes []Attribute) {
+	for _, a := range attributes {
+		m[a.key] = a.value
+	}
+}
+
+func (s *Span) lazyPrintfInternal(attributes []Attribute, format string, a ...interface{}) {
+	now := time.Now()
+	msg := fmt.Sprintf(format, a...)
+	var m map[string]interface{}
+	s.mu.Lock()
+	if len(attributes) != 0 {
+		m = make(map[string]interface{}, len(attributes))
+		copyAttributes(m, attributes)
+	}
+	s.annotations.add(Annotation{
+		Time:       now,
+		Message:    msg,
+		Attributes: m,
+	})
+	s.mu.Unlock()
+}
+
+func (s *Span) printStringInternal(attributes []Attribute, str string) {
+	now := time.Now()
+	var a map[string]interface{}
+	s.mu.Lock()
+	if len(attributes) != 0 {
+		a = make(map[string]interface{}, len(attributes))
+		copyAttributes(a, attributes)
+	}
+	s.annotations.add(Annotation{
+		Time:       now,
+		Message:    str,
+		Attributes: a,
+	})
+	s.mu.Unlock()
+}
+
+// Annotate adds an annotation with attributes.
+// Attributes can be nil.
+func (s *Span) Annotate(attributes []Attribute, str string) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.printStringInternal(attributes, str)
+}
+
+// Annotatef adds an annotation with attributes.
+func (s *Span) Annotatef(attributes []Attribute, format string, a ...interface{}) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.lazyPrintfInternal(attributes, format, a...)
+}
+
+// AddMessageSendEvent adds a message send event to the span.
+//
+// messageID is an identifier for the message, which is recommended to be
+// unique in this span and the same between the send event and the receive
+// event (this allows to identify a message between the sender and receiver).
+// For example, this could be a sequence id.
+func (s *Span) AddMessageSendEvent(messageID, uncompressedByteSize, compressedByteSize int64) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	now := time.Now()
+	s.mu.Lock()
+	s.messageEvents.add(MessageEvent{
+		Time:                 now,
+		EventType:            MessageEventTypeSent,
+		MessageID:            messageID,
+		UncompressedByteSize: uncompressedByteSize,
+		CompressedByteSize:   compressedByteSize,
+	})
+	s.mu.Unlock()
+}
+
+// AddMessageReceiveEvent adds a message receive event to the span.
+//
+// messageID is an identifier for the message, which is recommended to be
+// unique in this span and the same between the send event and the receive
+// event (this allows to identify a message between the sender and receiver).
+// For example, this could be a sequence id.
+func (s *Span) AddMessageReceiveEvent(messageID, uncompressedByteSize, compressedByteSize int64) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	now := time.Now()
+	s.mu.Lock()
+	s.messageEvents.add(MessageEvent{
+		Time:                 now,
+		EventType:            MessageEventTypeRecv,
+		MessageID:            messageID,
+		UncompressedByteSize: uncompressedByteSize,
+		CompressedByteSize:   compressedByteSize,
+	})
+	s.mu.Unlock()
+}
+
+// AddLink adds a link to the span.
+func (s *Span) AddLink(l Link) {
+	if !s.IsRecordingEvents() {
+		return
+	}
+	s.mu.Lock()
+	s.links.add(l)
+	s.mu.Unlock()
+}
+
+func (s *Span) String() string {
+	if s == nil {
+		return "<nil>"
+	}
+	if s.data == nil {
+		return fmt.Sprintf("span %s", s.spanContext.SpanID)
+	}
+	s.mu.Lock()
+	str := fmt.Sprintf("span %s %q", s.spanContext.SpanID, s.data.Name)
+	s.mu.Unlock()
+	return str
+}
+
+var config atomic.Value // access atomically
+
+func init() {
+	gen := &defaultIDGenerator{}
+	// initialize traceID and spanID generators.
+	var rngSeed int64
+	for _, p := range []interface{}{
+		&rngSeed, &gen.traceIDAdd, &gen.nextSpanID, &gen.spanIDInc,
+	} {
+		binary.Read(crand.Reader, binary.LittleEndian, p)
+	}
+	gen.traceIDRand = rand.New(rand.NewSource(rngSeed))
+	gen.spanIDInc |= 1
+
+	config.Store(&Config{
+		DefaultSampler:             ProbabilitySampler(defaultSamplingProbability),
+		IDGenerator:                gen,
+		MaxAttributesPerSpan:       DefaultMaxAttributesPerSpan,
+		MaxAnnotationEventsPerSpan: DefaultMaxAnnotationEventsPerSpan,
+		MaxMessageEventsPerSpan:    DefaultMaxMessageEventsPerSpan,
+		MaxLinksPerSpan:            DefaultMaxLinksPerSpan,
+	})
+}
+
+type defaultIDGenerator struct {
+	sync.Mutex
+
+	// Please keep these as the first fields
+	// so that these 8 byte fields will be aligned on addresses
+	// divisible by 8, on both 32-bit and 64-bit machines when
+	// performing atomic increments and accesses.
+	// See:
+	// * https://github.com/census-instrumentation/opencensus-go/issues/587
+	// * https://github.com/census-instrumentation/opencensus-go/issues/865
+	// * https://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	nextSpanID uint64
+	spanIDInc  uint64
+
+	traceIDAdd  [2]uint64
+	traceIDRand *rand.Rand
+}
+
+// NewSpanID returns a non-zero span ID from a randomly-chosen sequence.
+func (gen *defaultIDGenerator) NewSpanID() [8]byte {
+	var id uint64
+	for id == 0 {
+		id = atomic.AddUint64(&gen.nextSpanID, gen.spanIDInc)
+	}
+	var sid [8]byte
+	binary.LittleEndian.PutUint64(sid[:], id)
+	return sid
+}
+
+// NewTraceID returns a non-zero trace ID from a randomly-chosen sequence.
+// mu should be held while this function is called.
+func (gen *defaultIDGenerator) NewTraceID() [16]byte {
+	var tid [16]byte
+	// Construct the trace ID from two outputs of traceIDRand, with a constant
+	// added to each half for additional entropy.
+	gen.Lock()
+	binary.LittleEndian.PutUint64(tid[0:8], gen.traceIDRand.Uint64()+gen.traceIDAdd[0])
+	binary.LittleEndian.PutUint64(tid[8:16], gen.traceIDRand.Uint64()+gen.traceIDAdd[1])
+	gen.Unlock()
+	return tid
+}

vendor/go.opencensus.io/trace/trace_go11.go

@@ -0,0 +1,32 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.11
+
+package trace
+
+import (
+	"context"
+	t "runtime/trace"
+)
+
+func startExecutionTracerTask(ctx context.Context, name string) (context.Context, func()) {
+	if !t.IsEnabled() {
+		// Avoid additional overhead if
+		// runtime/trace is not enabled.
+		return ctx, func() {}
+	}
+	nctx, task := t.NewTask(ctx, name)
+	return nctx, task.End
+}

vendor/go.opencensus.io/trace/trace_nongo11.go

@@ -0,0 +1,25 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !go1.11
+
+package trace
+
+import (
+	"context"
+)
+
+func startExecutionTracerTask(ctx context.Context, name string) (context.Context, func()) {
+	return ctx, func() {}
+}

vendor/go.opencensus.io/trace/tracestate/tracestate.go

@@ -0,0 +1,147 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package tracestate implements support for the Tracestate header of the
+// W3C TraceContext propagation format.
+package tracestate
+
+import (
+	"fmt"
+	"regexp"
+)
+
+const (
+	keyMaxSize       = 256
+	valueMaxSize     = 256
+	maxKeyValuePairs = 32
+)
+
+const (
+	keyWithoutVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,255}`
+	keyWithVendorFormat    = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}`
+	keyFormat              = `(` + keyWithoutVendorFormat + `)|(` + keyWithVendorFormat + `)`
+	valueFormat            = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]`
+)
+
+var keyValidationRegExp = regexp.MustCompile(`^(` + keyFormat + `)$`)
+var valueValidationRegExp = regexp.MustCompile(`^(` + valueFormat + `)$`)
+
+// Tracestate represents tracing-system specific context in a list of key-value pairs. Tracestate allows different
+// vendors propagate additional information and inter-operate with their legacy Id formats.
+type Tracestate struct {
+	entries []Entry
+}
+
+// Entry represents one key-value pair in a list of key-value pair of Tracestate.
+type Entry struct {
+	// Key is an opaque string up to 256 characters printable. It MUST begin with a lowercase letter,
+	// and can only contain lowercase letters a-z, digits 0-9, underscores _, dashes -, asterisks *, and
+	// forward slashes /.
+	Key string
+
+	// Value is an opaque string up to 256 characters printable ASCII RFC0020 characters (i.e., the
+	// range 0x20 to 0x7E) except comma , and =.
+	Value string
+}
+
+// Entries returns a slice of Entry.
+func (ts *Tracestate) Entries() []Entry {
+	if ts == nil {
+		return nil
+	}
+	return ts.entries
+}
+
+func (ts *Tracestate) remove(key string) *Entry {
+	for index, entry := range ts.entries {
+		if entry.Key == key {
+			ts.entries = append(ts.entries[:index], ts.entries[index+1:]...)
+			return &entry
+		}
+	}
+	return nil
+}
+
+func (ts *Tracestate) add(entries []Entry) error {
+	for _, entry := range entries {
+		ts.remove(entry.Key)
+	}
+	if len(ts.entries)+len(entries) > maxKeyValuePairs {
+		return fmt.Errorf("adding %d key-value pairs to current %d pairs exceeds the limit of %d",
+			len(entries), len(ts.entries), maxKeyValuePairs)
+	}
+	ts.entries = append(entries, ts.entries...)
+	return nil
+}
+
+func isValid(entry Entry) bool {
+	return keyValidationRegExp.MatchString(entry.Key) &&
+		valueValidationRegExp.MatchString(entry.Value)
+}
+
+func containsDuplicateKey(entries ...Entry) (string, bool) {
+	keyMap := make(map[string]int)
+	for _, entry := range entries {
+		if _, ok := keyMap[entry.Key]; ok {
+			return entry.Key, true
+		}
+		keyMap[entry.Key] = 1
+	}
+	return "", false
+}
+
+func areEntriesValid(entries ...Entry) (*Entry, bool) {
+	for _, entry := range entries {
+		if !isValid(entry) {
+			return &entry, false
+		}
+	}
+	return nil, true
+}
+
+// New creates a Tracestate object from a parent and/or entries (key-value pair).
+// Entries from the parent are copied if present. The entries passed to this function
+// are inserted in front of those copied from the parent. If an entry copied from the
+// parent contains the same key as one of the entry in entries then the entry copied
+// from the parent is removed. See add func.
+//
+// An error is returned with nil Tracestate if
+//  1. one or more entry in entries is invalid.
+//  2. two or more entries in the input entries have the same key.
+//  3. the number of entries combined from the parent and the input entries exceeds maxKeyValuePairs.
+//     (duplicate entry is counted only once).
+func New(parent *Tracestate, entries ...Entry) (*Tracestate, error) {
+	if parent == nil && len(entries) == 0 {
+		return nil, nil
+	}
+	if entry, ok := areEntriesValid(entries...); !ok {
+		return nil, fmt.Errorf("key-value pair {%s, %s} is invalid", entry.Key, entry.Value)
+	}
+
+	if key, duplicate := containsDuplicateKey(entries...); duplicate {
+		return nil, fmt.Errorf("contains duplicate keys (%s)", key)
+	}
+
+	tracestate := Tracestate{}
+
+	if parent != nil && len(parent.entries) > 0 {
+		tracestate.entries = append([]Entry{}, parent.entries...)
+	}
+
+	err := tracestate.add(entries)
+	if err != nil {
+		return nil, err
+	}
+	return &tracestate, nil
+}