[receiver/opencensusreceiver] Fix memory leak on shutdown (#31152)

The opencensus receiver opens a few servers on `Start`, each of which
use the context's cancel to signal shutdown. Without cancelling the
context, the goroutines were being leaked. This change properly cancels
the context and shutdowns the receiver's servers.

This also enables `goleak` checks on the opencensus receiver and
exporter. I realize the exporter is not technically related here, but
its tests were what alerted me to the leak in the receiver. The
`TestSendTraces` and `TestSendMetrics` tests in the exporter were
starting opencensus receivers and exporters, and failing on leaks.

The change here is test-only for the exporter, and a bug fix for the
receiver.

#30438

All existing tests are passing, as well as added `goleak` checks.

.chloggen/goleak_opencensuscomps.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: opencensusreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix memory leak on shutdown
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [31152]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

exporter/opencensusexporter/go.mod

@@ -21,6 +21,7 @@ require (
 	go.opentelemetry.io/collector/receiver v0.94.1
 	go.opentelemetry.io/otel/metric v1.23.0
 	go.opentelemetry.io/otel/trace v1.23.0
+	go.uber.org/goleak v1.3.0
 	google.golang.org/grpc v1.61.0
 )
 

exporter/opencensusexporter/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package opencensusexporter
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}

receiver/opencensusreceiver/opencensus.go

@@ -37,6 +37,7 @@ type ocReceiver struct {
 	gatewayMux         *gatewayruntime.ServeMux
 	corsOrigins        []string
 	grpcServerSettings configgrpc.ServerConfig
+	cancel             context.CancelFunc
 
 	traceReceiver   *octrace.Receiver
 	metricsReceiver *ocmetrics.Receiver
@@ -192,6 +193,10 @@ func (ocr *ocReceiver) Shutdown(context.Context) error {
 	// tests and code should be reactive in less than even 1second.
 	// ocr.serverGRPC.Stop()
 
+	if ocr.cancel != nil {
+		ocr.cancel()
+	}
+
 	return err
 }
 
@@ -213,7 +218,8 @@ func (ocr *ocReceiver) httpServer() *http.Server {
 
 func (ocr *ocReceiver) startServer() error {
 	// Register the grpc-gateway on the HTTP server mux
-	c := context.Background()
+	var c context.Context
+	c, ocr.cancel = context.WithCancel(context.Background())
 	opts := []grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())}
 	endpoint := ocr.ln.Addr().String()
 

receiver/opencensusreceiver/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package opencensusreceiver
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}