[receiver/mongodbatlas] Fix memory leak (#32206)

**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.-->
The receiver was leaking goroutines by holding onto idle connections.
The solution is to reference the underlying `Transport` object, and call
`CloseIdleConnections` on it during shutdown.

This change also enables `goleak` on the MongoDB Atlas receiver to help
ensure no goroutines are being leaked.

**Link to tracking Issue:** <Issue number if applicable>
#30428

**Testing:** <Describe what testing was performed and which tests were
added.>
All existing tests are passing, as well as added `goleak` checks.

.chloggen/goleak_mongodbatlas.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: mongodbatlasreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix memory leak by closing idle connections on shutdown
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [32206]
+
+# (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: [user]

receiver/mongodbatlasreceiver/events.go

@@ -6,6 +6,7 @@ package mongodbatlasreceiver // import "github.com/open-telemetry/opentelemetry-
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -34,6 +35,7 @@ type eventsClient interface {
 	GetProjectEvents(ctx context.Context, groupID string, opts *internal.GetEventsOptions) (ret []*mongodbatlas.Event, nextPage bool, err error)
 	GetOrganization(ctx context.Context, orgID string) (*mongodbatlas.Organization, error)
 	GetOrganizationEvents(ctx context.Context, orgID string, opts *internal.GetEventsOptions) (ret []*mongodbatlas.Event, nextPage bool, err error)
+	Shutdown() error
 }
 
 type eventsReceiver struct {
@@ -97,7 +99,12 @@ func (er *eventsReceiver) Shutdown(ctx context.Context) error {
 	er.logger.Debug("Shutting down events receiver")
 	er.cancel()
 	er.wg.Wait()
-	return er.checkpoint(ctx)
+
+	var err []error
+	err = append(err, er.client.Shutdown())
+	err = append(err, er.checkpoint(ctx))
+
+	return errors.Join(err...)
 }
 
 func (er *eventsReceiver) startPolling(ctx context.Context) error {

receiver/mongodbatlasreceiver/events_test.go

@@ -164,16 +164,14 @@ func TestProjectGetFailure(t *testing.T) {
 	mClient := &mockEventsClient{}
 	mClient.On("GetProject", mock.Anything, "fake-project").Return(nil, fmt.Errorf("unable to get project: %d", http.StatusUnauthorized))
 	mClient.On("GetOrganization", mock.Anything, "fake-org").Return(nil, fmt.Errorf("unable to get org: %d", http.StatusUnauthorized))
+	mClient.setupMock(t)
+	r.client = mClient
 
-	err := r.Start(context.Background(), componenttest.NewNopHost(), storage.NewNopClient())
-	require.NoError(t, err)
-
+	require.NoError(t, r.Start(context.Background(), componenttest.NewNopHost(), storage.NewNopClient()))
 	require.Never(t, func() bool {
 		return sink.LogRecordCount() > 0
 	}, 2*time.Second, 500*time.Millisecond)
-
-	err = r.Shutdown(context.Background())
-	require.NoError(t, err)
+	require.NoError(t, r.Shutdown(context.Background()))
 }
 
 type mockEventsClient struct {
@@ -216,7 +214,12 @@ func (mec *mockEventsClient) loadTestEvents(t *testing.T, filename string) []*mo
 
 func (mec *mockEventsClient) GetProject(ctx context.Context, pID string) (*mongodbatlas.Project, error) {
 	args := mec.Called(ctx, pID)
-	return args.Get(0).(*mongodbatlas.Project), args.Error(1)
+	receivedProject := args.Get(0)
+	if receivedProject == nil {
+		return nil, args.Error(1)
+	}
+
+	return receivedProject.(*mongodbatlas.Project), args.Error(1)
 }
 
 func (mec *mockEventsClient) GetProjectEvents(ctx context.Context, pID string, opts *internal.GetEventsOptions) ([]*mongodbatlas.Event, bool, error) {
@@ -233,3 +236,7 @@ func (mec *mockEventsClient) GetOrganizationEvents(ctx context.Context, oID stri
 	args := mec.Called(ctx, oID, opts)
 	return args.Get(0).([]*mongodbatlas.Event), args.Bool(1), args.Error(2)
 }
+
+func (mec *mockEventsClient) Shutdown() error {
+	return nil
+}

receiver/mongodbatlasreceiver/internal/mongodb_atlas_client.go

@@ -123,6 +123,7 @@ func (rt *clientRoundTripper) RoundTrip(r *http.Request) (*http.Response, error)
 type MongoDBAtlasClient struct {
 	log          *zap.Logger
 	client       *mongodbatlas.Client
+	transport    *http.Transport
 	roundTripper *clientRoundTripper
 }
 
@@ -133,18 +134,21 @@ func NewMongoDBAtlasClient(
 	backoffConfig configretry.BackOffConfig,
 	log *zap.Logger,
 ) *MongoDBAtlasClient {
-	t := digest.NewTransport(publicKey, privateKey)
+	defaultTransporter := &http.Transport{}
+	t := digest.NewTransportWithHTTPTransport(publicKey, privateKey, defaultTransporter)
 	roundTripper := newClientRoundTripper(t, log, backoffConfig)
 	tc := &http.Client{Transport: roundTripper}
 	client := mongodbatlas.NewClient(tc)
 	return &MongoDBAtlasClient{
 		log,
 		client,
+		defaultTransporter,
 		roundTripper,
 	}
 }
 
 func (s *MongoDBAtlasClient) Shutdown() error {
+	s.transport.CloseIdleConnections()
 	return s.roundTripper.Shutdown()
 }
 

receiver/mongodbatlasreceiver/package_test.go

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

receiver/mongodbatlasreceiver/receiver_test.go

@@ -18,14 +18,18 @@ func TestDefaultConfig(t *testing.T) {
 	factory := NewFactory()
 	cfg := factory.CreateDefaultConfig()
 	require.Equal(t, cfg.(*Config).ControllerConfig.CollectionInterval, 3*time.Minute)
-	recv, err := createMetricsReceiver(context.Background(), receivertest.NewNopCreateSettings(), cfg, consumertest.NewNop())
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	recv, err := createMetricsReceiver(ctx, receivertest.NewNopCreateSettings(), cfg, consumertest.NewNop())
 	require.NoError(t, err)
 	require.NotNil(t, recv, "receiver creation failed")
 
-	err = recv.Start(context.Background(), componenttest.NewNopHost())
+	err = recv.Start(ctx, componenttest.NewNopHost())
 	require.NoError(t, err)
 
-	err = recv.Shutdown(context.Background())
+	err = recv.Shutdown(ctx)
 	require.NoError(t, err)
 }