Application default credentials for Stackdriver (#501)

Author: Ramon Nogueira

exporter/stackdriver/example_test.go

@@ -33,6 +33,8 @@ func Example() {
 
 	// Export to Stackdriver Monitoring.
 	view.RegisterExporter(exporter)
+	// Subscribe views to see stats in Stackdriver Monitoring
+	view.Subscribe(ochttp.ClientLatencyView, ochttp.ClientResponseBytesView)
 
 	// Export to Stackdriver Trace.
 	trace.RegisterExporter(exporter)

exporter/stackdriver/stackdriver.go

@@ -22,10 +22,15 @@
 package stackdriver // import "go.opencensus.io/exporter/stackdriver"
 
 import (
+	"context"
+	"errors"
+	"fmt"
 	"time"
 
+	traceapi "cloud.google.com/go/trace/apiv2"
 	"go.opencensus.io/stats/view"
 	"go.opencensus.io/trace"
+	"golang.org/x/oauth2/google"
 	"google.golang.org/api/option"
 	monitoredrespb "google.golang.org/genproto/googleapis/api/monitoredres"
 )
@@ -34,10 +39,12 @@ import (
 type Options struct {
 	// ProjectID is the identifier of the Stackdriver
 	// project the user is uploading the stats data to.
+	// If not set, this will default to your "Application Default Credentials".
+	// For details see: https://developers.google.com/accounts/docs/application-default-credentials
 	ProjectID string
 
 	// OnError is the hook to be called when there is
-	// an error occurred when uploading the stats data.
+	// an error uploading the stats or tracing data.
 	// If no custom hook is set, errors are logged.
 	// Optional.
 	OnError func(err error)
@@ -76,6 +83,16 @@ type Exporter struct {
 // NewExporter creates a new Exporter that implements both stats.Exporter and
 // trace.Exporter.
 func NewExporter(o Options) (*Exporter, error) {
+	if o.ProjectID == "" {
+		creds, err := google.FindDefaultCredentials(context.Background(), traceapi.DefaultAuthScopes()...)
+		if err != nil {
+			return nil, fmt.Errorf("stackdriver: %v", err)
+		}
+		if creds.ProjectID == "" {
+			return nil, errors.New("stackdriver: no project found with application default credentials")
+		}
+		o.ProjectID = creds.ProjectID
+	}
 	se, err := newStatsExporter(o)
 	if err != nil {
 		return nil, err

exporter/stackdriver/stackdriver_test.go

@@ -0,0 +1,79 @@
+// 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 stackdriver
+
+import (
+	"context"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"go.opencensus.io/plugin/ochttp"
+	"go.opencensus.io/stats/view"
+	"go.opencensus.io/trace"
+	"golang.org/x/net/context/ctxhttp"
+)
+
+func TestExport(t *testing.T) {
+	projectID, ok := os.LookupEnv("STACKDRIVER_TEST_PROJECT_ID")
+	if !ok {
+		t.Skip("STACKDRIVER_TEST_PROJECT_ID not set")
+	}
+
+	exporter, err := NewExporter(Options{ProjectID: projectID})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer exporter.Flush()
+
+	trace.RegisterExporter(exporter)
+	defer trace.UnregisterExporter(exporter)
+	view.RegisterExporter(exporter)
+	defer view.UnregisterExporter(exporter)
+
+	trace.SetDefaultSampler(trace.AlwaysSample())
+
+	span := trace.NewSpan("custom-span", nil, trace.StartOptions{})
+	time.Sleep(10 * time.Millisecond)
+	span.End()
+
+	// Test HTTP spans
+
+	handler := http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		time.Sleep(150 * time.Millisecond) // do work
+		rw.Write([]byte("Hello, world!"))
+	})
+	server := httptest.NewServer(&ochttp.Handler{Handler: handler})
+	defer server.Close()
+
+	ctx := context.Background()
+	client := &http.Client{
+		Transport: &ochttp.Transport{},
+	}
+	resp, err := ctxhttp.Get(ctx, client, server.URL+"/test/123?abc=xyz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want, got := "Hello, world!", string(body); want != got {
+		t.Fatalf("resp.Body = %q; want %q", want, got)
+	}
+}