client: add extended http client for making omaha api requests

Supports encoding/decoding omaha xml and retrying on transient failures.

omaha/client/http.go

@@ -0,0 +1,78 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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 client
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/coreos/go-omaha/omaha"
+)
+
+const (
+	defaultTimeout = 90 * time.Second
+	defaultTries   = 7
+)
+
+// httpClient extends the standard http.Client to support xml encoding
+// and decoding as well as automatic retries on transient failures.
+type httpClient struct {
+	http.Client
+}
+
+func newHTTPClient() *httpClient {
+	return &httpClient{http.Client{
+		Timeout: defaultTimeout,
+	}}
+}
+
+// doPost sends a single HTTP POST, returning a parsed omaha response.
+func (hc *httpClient) doPost(url string, reqBody []byte) (*omaha.Response, error) {
+	resp, err := hc.Post(url, "text/xml; charset=utf-8", bytes.NewReader(reqBody))
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	contentType := resp.Header.Get("Content-Type")
+	return omaha.ParseResponse(contentType, resp.Body)
+}
+
+// Omaha encodes and sends an omaha request, retrying on any transient errors.
+func (hc *httpClient) Omaha(url string, req *omaha.Request) (resp *omaha.Response, err error) {
+	buf := bytes.NewBufferString(xml.Header)
+	enc := xml.NewEncoder(buf)
+	if err := enc.Encode(req); err != nil {
+		return nil, fmt.Errorf("omaha: failed to encode request: %v", err)
+	}
+
+	for i := 0; i < defaultTries; i++ {
+		resp, err = hc.doPost(url, buf.Bytes())
+		if neterr, ok := err.(net.Error); ok && neterr.Temporary() {
+			// TODO(marineam): add exponential backoff
+			continue
+		}
+		break
+	}
+	if err != nil {
+		return nil, fmt.Errorf("omaha: request failed: %v", err)
+	}
+
+	return resp, nil
+}

omaha/client/http_test.go

@@ -0,0 +1,57 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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 client
+
+import (
+	"testing"
+
+	"github.com/coreos/go-omaha/omaha"
+)
+
+const (
+	sampleRequest = `<?xml version="1.0" encoding="UTF-8"?>
+<request protocol="3.0" version="ChromeOSUpdateEngine-0.1.0.0" updaterversion="ChromeOSUpdateEngine-0.1.0.0" installsource="ondemandupdate" ismachine="1">
+<os version="Indy" platform="Chrome OS" sp="ForcedUpdate_x86_64"></os>
+<app appid="{87efface-864d-49a5-9bb3-4b050a7c227a}" bootid="{7D52A1CC-7066-40F0-91C7-7CB6A871BFDE}" machineid="{8BDE4C4D-9083-4D61-B41C-3253212C0C37}" oem="ec3000" version="ForcedUpdate" track="dev-channel" from_track="developer-build" lang="en-US" board="amd64-generic" hardware_class="" delta_okay="false" >
+<ping active="1" a="-1" r="-1"></ping>
+<updatecheck targetversionprefix=""></updatecheck>
+<event eventtype="3" eventresult="2" previousversion=""></event>
+</app>
+</request>
+`
+)
+
+func TestHTTPClientDoPost(t *testing.T) {
+	s, err := omaha.NewTrivialServer("127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s.Destroy()
+	go s.Serve()
+
+	c := newHTTPClient()
+	url := "http://" + s.Addr().String() + "/v1/update/"
+
+	resp, err := c.doPost(url, []byte(sampleRequest))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(resp.Apps) != 1 {
+		t.Fatalf("Should be 1 app, not %d", len(resp.Apps))
+	}
+	if resp.Apps[0].Status != omaha.AppOK {
+		t.Fatalf("Bad apps status: %q", resp.Apps[0].Status)
+	}
+}