fix(controller): race condition in handleSigterm() test

Fix a race condition between the signal handler setup and the signal
send in the test for handleSigterm()

Author: vflaux

controller/execute.go

@@ -100,7 +100,7 @@ func Execute() {
 	ctx, cancel := context.WithCancel(context.Background())
 
 	go serveMetrics(cfg.MetricsAddress)
-	go handleSigterm(cancel)
+	setupSigtermHandler(cancel)
 
 	endpointsSource, err := buildSource(ctx, cfg)
 	if err != nil {
@@ -470,14 +470,23 @@ func createDomainFilter(cfg *externaldns.Config) *endpoint.DomainFilter {
 
 // handleSigterm listens for a SIGTERM signal and triggers the provided cancel function
 // to gracefully terminate the application. It logs a message when the signal is received.
-func handleSigterm(cancel func()) {
+// The setupCh channel is used to signal when the signal handler is ready to receive signals.
+func handleSigterm(cancel func(), setupCh chan struct{}) {
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGTERM)
+	close(setupCh)
 	<-signals
 	log.Info("Received SIGTERM. Terminating...")
 	cancel()
 }
 
+// setupSigtermHandler initializes the SIGTERM handler in a separate goroutine and waits for it to be ready.
+func setupSigtermHandler(cancel func()) {
+	setupCh := make(chan struct{})
+	go handleSigterm(cancel, setupCh)
+	<-setupCh
+}
+
 // serveMetrics starts an HTTP server that serves health and metrics endpoints.
 // The /healthz endpoint returns a 200 OK status to indicate the service is healthy.
 // The /metrics endpoint serves Prometheus metrics.

controller/execute_test.go

@@ -189,7 +189,7 @@ func TestCreateDomainFilter(t *testing.T) {
 	}
 }
 
-func TestHandleSigterm(t *testing.T) {
+func TestSetupSigterm(t *testing.T) {
 	cancelCalled := make(chan bool, 1)
 	cancel := func() {
 		cancelCalled <- true
@@ -199,20 +199,26 @@ func TestHandleSigterm(t *testing.T) {
 	log.SetOutput(&logOutput)
 	defer log.SetOutput(os.Stderr)
 
-	go handleSigterm(cancel)
+	setupSigtermHandler(cancel)
 
 	// Simulate sending a SIGTERM signal
 	sigChan := make(chan os.Signal, 1)
 	signal.Notify(sigChan, syscall.SIGTERM)
 	err := syscall.Kill(syscall.Getpid(), syscall.SIGTERM)
 	assert.NoError(t, err)
 
+	// Wait for the signal to be received
+	select {
+	case sig := <-sigChan:
+		assert.Equal(t, syscall.SIGTERM, sig)
+	case <-time.After(1 * time.Second):
+		t.Fatal("signal was not recieved")
+	}
+
 	// Wait for the cancel function to be called
 	select {
 	case <-cancelCalled:
 		assert.Contains(t, logOutput.String(), "Received SIGTERM. Terminating...")
-	case sig := <-sigChan:
-		assert.Equal(t, syscall.SIGTERM, sig)
 	case <-time.After(1 * time.Second):
 		t.Fatal("cancel function was not called")
 	}