Fix flakiness in TestManager_NoDeadlock (#4104)

pkg/component/runtime/manager_fake_input_test.go

@@ -1307,35 +1307,11 @@ LOOP:
 	require.Equal(t, context.Canceled, err, "Run should return with context canceled, got %v", err.Error())
 }
 
-func (suite *FakeInputSuite) TestManager_NoDeadlock() {
-	t := suite.T()
-	// NOTE: This is a long-running test that spams the runtime managers `Update` function to try and
-	// trigger a deadlock. This test takes 2 minutes to run trying to re-produce issue:
-	// https://github.com/elastic/elastic-agent/issues/2691
-
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
-
-	ai, _ := info.NewAgentInfo(ctx, true)
-	m, err := NewManager(newDebugLogger(t), newDebugLogger(t), "localhost:0", ai, apmtest.DiscardTracer, newTestMonitoringMgr(), configuration.DefaultGRPCConfig())
-	require.NoError(t, err)
-	errCh := make(chan error)
-	go func() {
-		err := m.Run(ctx)
-		if errors.Is(err, context.Canceled) {
-			err = nil
-		}
-		errCh <- err
-	}()
-
-	waitCtx, waitCancel := context.WithTimeout(ctx, 1*time.Second)
-	defer waitCancel()
-	if err := waitForReady(waitCtx, m); err != nil {
-		require.NoError(t, err)
-	}
-
+// A component that can be fed to Manager.Update, with an index to allow
+// looping with distinct configurations at each step.
+func noDeadlockTestComponent(t *testing.T, index int) component.Component {
 	binaryPath := testBinary(t, "component")
-	comp := component.Component{
+	return component.Component{
 		ID: "fake-default",
 		InputSpec: &component.InputRuntimeSpec{
 			InputType:  "fake",
@@ -1351,99 +1327,92 @@ func (suite *FakeInputSuite) TestManager_NoDeadlock() {
 				Config: component.MustExpectedConfig(map[string]interface{}{
 					"type":    "fake",
 					"state":   int(client.UnitStateHealthy),
-					"message": "Fake Healthy",
+					"message": fmt.Sprintf("Fake Healthy %d", index),
 				}),
 			},
 		},
 	}
+}
 
-	updatedCh := make(chan time.Time)
-	updatedErr := make(chan error)
-	updatedCtx, updatedCancel := context.WithCancel(context.Background())
-	defer updatedCancel()
+func (suite *FakeInputSuite) TestManager_NoDeadlock() {
+	t := suite.T()
+	// NOTE: This is a long-running test that spams the runtime managers `Update` function to try and
+	// trigger a deadlock. This test takes 2 minutes to run trying to re-produce issue:
+	// https://github.com/elastic/elastic-agent/issues/2691
+
+	// How long to run the test
+	testDuration := 2 * time.Minute
+
+	// How long without an update before we report it as a deadlock
+	maxUpdateInterval := 15 * time.Second
+
+	// Create the runtime manager
+	ai, _ := info.NewAgentInfo(context.Background(), true)
+	m, err := NewManager(newDebugLogger(t), newDebugLogger(t), "localhost:0", ai, apmtest.DiscardTracer, newTestMonitoringMgr(), configuration.DefaultGRPCConfig())
+	require.NoError(t, err)
+
+	// Start the runtime manager in a goroutine, passing its termination state
+	// to managerResultChan.
+	managerCtx, managerCancel := context.WithCancel(context.Background())
+	defer managerCancel()
+	managerResultChan := make(chan error)
 	go func() {
-		// spam update on component trying to cause a deadlock
-		comp := comp
-		i := 0
-		for {
-			if updatedCtx.Err() != nil {
-				return
-			}
-			updatedComp := comp
-			updatedComp.Units = make([]component.Unit, 1)
-			updatedComp.Units[0] = component.Unit{
-				ID:       "fake-input",
-				Type:     client.UnitTypeInput,
-				LogLevel: client.UnitLogLevelError, // test log will get spammed with the constant updates (error to prevent spam)
-				Config: component.MustExpectedConfig(map[string]interface{}{
-					"type":    "fake",
-					"state":   int(client.UnitStateHealthy),
-					"message": fmt.Sprintf("Fake Healthy %d", i),
-				}),
-			}
-			i += 1
-			comp = updatedComp
-			m.Update(component.Model{Components: []component.Component{updatedComp}})
-			err := <-m.errCh
-			if err != nil {
-				updatedErr <- err
-				return
-			}
-			updatedCh <- time.Now()
-		}
+		managerResultChan <- m.Run(managerCtx)
 	}()
 
-	deadlockErr := make(chan error)
+	// Wait for the manager to become active
+	timedWaitForReady(t, m, 1*time.Second)
+
+	// Start a goroutine to spam the manager update trying to cause
+	// a deadlock. When the test context finishes, the update loop
+	// closes updateResultChan to signal that it is done.
+	updateResultChan := make(chan error)
+	updateLoopCtx, updateLoopCancel := context.WithTimeout(context.Background(), testDuration)
+	defer updateLoopCancel()
 	go func() {
-		t := time.NewTimer(15 * time.Second)
-		defer t.Stop()
-		for {
-			select {
-			case <-updatedCtx.Done():
-				return
-			case <-updatedCh:
-				// update did occur
-				t.Reset(15 * time.Second)
-			case <-t.C:
-				// timeout hit waiting for another update to work
-				deadlockErr <- errors.New("hit deadlock")
+		defer close(updateResultChan)
+		for i := 0; updateLoopCtx.Err() == nil; i++ {
+			comp := noDeadlockTestComponent(t, i)
+			m.Update(component.Model{Components: []component.Component{comp}})
+			err := <-m.errCh
+			updateResultChan <- err
+			if err != nil {
+				// If the update gave an error, end the test
 				return
 			}
 		}
 	}()
 
-	defer drainErrChan(errCh)
-	defer drainErrChan(updatedErr)
-	defer drainErrChan(deadlockErr)
-
-	// wait 2 minutes for a deadlock to occur
-	endTimer := time.NewTimer(2 * time.Minute)
-	defer endTimer.Stop()
+	// The component state is being changed constantly. If updateTimeout
+	// triggers without any updates, report it as a deadlock.
+	updateTimeout := time.NewTicker(maxUpdateInterval)
+	defer updateTimeout.Stop()
 LOOP:
 	for {
 		select {
-		case <-endTimer.C:
-			// no deadlock after timeout (all good stop the component)
-			updatedCancel()
-			m.Update(component.Model{Components: []component.Component{}})
-			<-m.errCh // Don't care about the result of Update, just that it runs
-			break LOOP
-		case err := <-errCh:
-			require.NoError(t, err)
-		case err := <-updatedErr:
-			require.NoError(t, err)
-			break LOOP
-		case err := <-deadlockErr:
-			require.NoError(t, err)
-			break LOOP
+		case err, ok := <-updateResultChan:
+			if ok {
+				// update did occur
+				require.NoError(t, err)
+				updateTimeout.Reset(15 * time.Second)
+			} else {
+				// Update goroutine is terminating, test is over
+				break LOOP
+			}
+		case <-managerResultChan:
+			require.Fail(t, "Runtime manager terminated before test was over")
+		case <-updateTimeout.C:
+			require.Fail(t, "Timed out waiting for Manager.Update result")
 		}
 	}
-
-	updatedCancel()
-	cancel()
-
-	err = <-errCh
+	// Finished without a deadlock. Stop the component and shut down the manager.
+	m.Update(component.Model{Components: []component.Component{}})
+	err = <-m.errCh
 	require.NoError(t, err)
+
+	managerCancel()
+	err = <-managerResultChan
+	require.Equal(t, err, context.Canceled)
 }
 
 func (suite *FakeInputSuite) TestManager_Configure() {