Add test for stdout scanner race with runner.Wait() (#300)

client_test.go

@@ -28,10 +28,12 @@ import (
 
 func TestClient(t *testing.T) {
 	process := helperProcess("mock")
+	logger := &trackingLogger{Logger: hclog.Default()}
 	c := NewClient(&ClientConfig{
 		Cmd:             process,
 		HandshakeConfig: testHandshake,
 		Plugins:         testPluginMap,
+		Logger:          logger,
 	})
 	defer c.Kill()
 
@@ -61,6 +63,9 @@ func TestClient(t *testing.T) {
 	if !c.killed() {
 		t.Fatal("Client should have failed")
 	}
+
+	// One error for connection refused, one for plugin exited.
+	assertLines(t, logger.errorLogs, 2)
 }
 
 // This tests a bug where Kill would start
@@ -112,19 +117,19 @@ func TestClient_killStart(t *testing.T) {
 }
 
 func TestClient_testCleanup(t *testing.T) {
-	// Create a temporary dir to store the result file
-	td := t.TempDir()
-	defer os.RemoveAll(td)
+	t.Parallel()
 
 	// Create a path that the helper process will write on cleanup
-	path := filepath.Join(td, "output")
+	path := filepath.Join(t.TempDir(), "output")
 
 	// Test the cleanup
 	process := helperProcess("cleanup", path)
+	logger := &trackingLogger{Logger: hclog.Default()}
 	c := NewClient(&ClientConfig{
 		Cmd:             process,
 		HandshakeConfig: testHandshake,
 		Plugins:         testPluginMap,
+		Logger:          logger,
 	})
 
 	// Grab the client so the process starts
@@ -140,6 +145,61 @@ func TestClient_testCleanup(t *testing.T) {
 	if _, err := os.Stat(path); err != nil {
 		t.Fatalf("err: %s", err)
 	}
+
+	assertLines(t, logger.errorLogs, 0)
+}
+
+func TestClient_noStdoutScannerRace(t *testing.T) {
+	t.Parallel()
+
+	process := helperProcess("test-grpc")
+	logger := &trackingLogger{Logger: hclog.Default()}
+	c := NewClient(&ClientConfig{
+		RunnerFunc: func(l hclog.Logger, cmd *exec.Cmd, tmpDir string) (runner.Runner, error) {
+			process.Env = append(process.Env, cmd.Env...)
+			concreteRunner, err := cmdrunner.NewCmdRunner(l, process)
+			if err != nil {
+				return nil, err
+			}
+			// Inject a delay before calling .Read() method on the command's
+			// stdout reader. This ensures that if there is a race between the
+			// stdout scanner loop reading stdout and runner.Wait() closing
+			// stdout, .Wait() will win and trigger a scanner error in the logs.
+			return &delayedStdoutCmdRunner{concreteRunner}, nil
+		},
+		HandshakeConfig:  testHandshake,
+		Plugins:          testGRPCPluginMap,
+		AllowedProtocols: []Protocol{ProtocolGRPC},
+		Logger:           logger,
+	})
+
+	// Grab the client so the process starts
+	if _, err := c.Client(); err != nil {
+		c.Kill()
+		t.Fatalf("err: %s", err)
+	}
+
+	// Kill it gracefully
+	c.Kill()
+
+	assertLines(t, logger.errorLogs, 0)
+}
+
+type delayedStdoutCmdRunner struct {
+	*cmdrunner.CmdRunner
+}
+
+func (m *delayedStdoutCmdRunner) Stdout() io.ReadCloser {
+	return &delayedReader{m.CmdRunner.Stdout()}
+}
+
+type delayedReader struct {
+	io.ReadCloser
+}
+
+func (d *delayedReader) Read(p []byte) (n int, err error) {
+	time.Sleep(100 * time.Millisecond)
+	return d.ReadCloser.Read(p)
 }
 
 func TestClient_testInterface(t *testing.T) {
@@ -1563,3 +1623,23 @@ func TestClient_logStderrParseJSON(t *testing.T) {
 		}
 	}
 }
+
+type trackingLogger struct {
+	hclog.Logger
+	errorLogs []string
+}
+
+func (l *trackingLogger) Error(msg string, args ...interface{}) {
+	l.errorLogs = append(l.errorLogs, fmt.Sprintf("%s: %v", msg, args))
+	l.Logger.Error(msg, args...)
+}
+
+func assertLines(t *testing.T, lines []string, expected int) {
+	t.Helper()
+	if len(lines) != expected {
+		t.Errorf("expected %d, got %d", expected, len(lines))
+		for _, log := range lines {
+			t.Error(log)
+		}
+	}
+}