[exporter/signalfx] Fix memory leaks (open-telemetry#31772)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Changes in PR:

1. Add correlation client Shutdown function that blocks on the
waitgroup. This is the main fix of this PR that should fix the leaking
goroutines.
2. Re-organize the shutdown process of the apm client correlation test
suite to properly synchronize the shutting down process.
3. Fix typo
4. Only block request sender until context is cancelled. The request
processor is shutdown when the context is cancelled, so this would
result in `Shutdown` waiting forever, since the request would never be
processed.
5. Enable goleak in some more packages.

**Note**: This is contains the exact same contents as
open-telemetry#30887,
but change number 4 is new, and should resolve the test issue the
original PR was causing.

**Link to tracking Issue:**
Resolves
open-telemetry#30864

open-telemetry#30438

**Testing:** <Describe what testing was performed and which tests were
added.>
All existing tests are passing, as well as added goleak checks. I'm
going to run this a number of times to try to help ensure it's not flaky
anymore.

.chloggen/goleak_signalfx_correlations.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: signalfxexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix memory leak in shutdown
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [30864, 30438]
+
+# (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/signalfxexporter/internal/apm/correlations/client.go

@@ -44,6 +44,7 @@ type CorrelationClient interface {
 	Delete(*Correlation, SuccessfulDeleteCB)
 	Get(dimName string, dimValue string, cb SuccessfulGetCB)
 	Start()
+	Shutdown()
 }
 
 type request struct {
@@ -387,3 +388,9 @@ func (cc *Client) Start() {
 	go cc.processChan()
 	go cc.processRetryChan()
 }
+
+// Shutdown the client. This will block until the context's cancel
+// function is complete.
+func (cc *Client) Shutdown() {
+	cc.wg.Wait()
+}

exporter/signalfxexporter/internal/apm/correlations/client_test.go

@@ -124,18 +124,14 @@ func makeHandler(t *testing.T, corCh chan<- *request, forcedRespCode *atomic.Val
 	})
 }
 
-func setup(t *testing.T) (CorrelationClient, chan *request, *atomic.Value, *atomic.Value, context.CancelFunc) {
+func setup(t *testing.T) (CorrelationClient, *httptest.Server, chan *request, *atomic.Value, *atomic.Value, context.CancelFunc, context.Context) {
 	serverCh := make(chan *request, 100)
 
 	var forcedRespCode atomic.Value
 	var forcedRespPayload atomic.Value
 	server := httptest.NewServer(makeHandler(t, serverCh, &forcedRespCode, &forcedRespPayload))
 
 	ctx, cancel := context.WithCancel(context.Background())
-	go func() {
-		<-ctx.Done()
-		server.Close()
-	}()
 
 	serverURL, err := url.Parse(server.URL)
 	if err != nil {
@@ -176,13 +172,20 @@ func setup(t *testing.T) (CorrelationClient, chan *request, *atomic.Value, *atom
 	}
 	client.Start()
 
-	return client, serverCh, &forcedRespCode, &forcedRespPayload, cancel
+	return client, server, serverCh, &forcedRespCode, &forcedRespPayload, cancel, ctx
+}
+
+func teardown(ctx context.Context, client CorrelationClient, server *httptest.Server, serverCh chan *request, cancel context.CancelFunc) {
+	close(serverCh)
+	cancel()
+	<-ctx.Done()
+	client.Shutdown()
+	server.Close()
 }
 
 func TestCorrelationClient(t *testing.T) {
-	client, serverCh, forcedRespCode, forcedRespPayload, cancel := setup(t)
-	defer close(serverCh)
-	defer cancel()
+	client, server, serverCh, forcedRespCode, forcedRespPayload, cancel, ctx := setup(t)
+	defer teardown(ctx, client, server, serverCh, cancel)
 
 	for _, correlationType := range []Type{Service, Environment} {
 		for _, op := range []string{http.MethodPut, http.MethodDelete} {
@@ -242,7 +245,7 @@ func TestCorrelationClient(t *testing.T) {
 		client.Correlate(testData, CorrelateCB(func(_ *Correlation, _ error) {}))
 		// sending the testData twice tests deduplication, since the 500 status
 		// will trigger retries, and the requests should be deduped and the
-		// TotalRertriedUpdates should still only be 5
+		// TotalRetriedUpdates should still only be 5
 		client.Correlate(testData, CorrelateCB(func(_ *Correlation, _ error) {}))
 
 		cors := waitForCors(serverCh, 1, 4)

exporter/signalfxexporter/internal/apm/correlations/package_test.go

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

exporter/signalfxexporter/internal/apm/requests/sender.go

@@ -48,8 +48,14 @@ func (rs *ReqSender) Send(req *http.Request) {
 			go rs.processRequests()
 		}
 
-		// Block until we can get through a request
-		rs.requests <- req
+		// Block until we can get the request through, or until the context is cancelled. The request processor
+		// shuts down when the context has been cancelled, so there's no value added to keep blocking. Blocking
+		// forever results in Shutdown never completing.
+		select {
+		case <-rs.ctx.Done():
+			return
+		case rs.requests <- req:
+		}
 	}
 }
 

exporter/signalfxexporter/internal/apm/tracetracker/tracker_test.go

@@ -85,7 +85,8 @@ type correlationTestClient struct {
 	correlateCounter int64
 }
 
-func (c *correlationTestClient) Start() { /*no-op*/ }
+func (c *correlationTestClient) Start()    { /*no-op*/ }
+func (c *correlationTestClient) Shutdown() { /*no-op*/ }
 func (c *correlationTestClient) Get(_ string, dimValue string, cb correlations.SuccessfulGetCB) {
 	atomic.AddInt64(&c.getCounter, 1)
 	go func() {

exporter/signalfxexporter/internal/correlation/correlation.go

@@ -137,6 +137,7 @@ func (cor *Tracker) Shutdown(_ context.Context) error {
 	if cor != nil {
 		if cor.correlation != nil {
 			cor.correlation.cancel()
+			cor.correlation.CorrelationClient.Shutdown()
 		}
 
 		if cor.pTicker != nil {

exporter/signalfxexporter/internal/correlation/correlation_test.go

@@ -86,6 +86,8 @@ func TestTrackerStart(t *testing.T) {
 			} else {
 				require.NoError(t, err)
 			}
+
+			assert.NoError(t, tracker.Shutdown(context.Background()))
 		})
 	}
 }

exporter/signalfxexporter/internal/correlation/package_test.go

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