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

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

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)
+}