Fix goroutine leak on logs -f with no output

Also noticed potential hang when only stdout or stderr are used with
follow=1

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

api/server/server.go

@@ -597,6 +597,11 @@ func (s *Server) getContainersLogs(version version.Version, w http.ResponseWrite
 		since = time.Unix(s, 0)
 	}
 
+	var closeNotifier <-chan bool
+	if notifier, ok := w.(http.CloseNotifier); ok {
+		closeNotifier = notifier.CloseNotify()
+	}
+
 	logsConfig := &daemon.ContainerLogsConfig{
 		Follow:     boolValue(r, "follow"),
 		Timestamps: boolValue(r, "timestamps"),
@@ -605,6 +610,7 @@ func (s *Server) getContainersLogs(version version.Version, w http.ResponseWrite
 		UseStdout:  stdout,
 		UseStderr:  stderr,
 		OutStream:  ioutils.NewWriteFlusher(w),
+		Stop:       closeNotifier,
 	}
 
 	if err := s.daemon.ContainerLogs(vars["name"], logsConfig); err != nil {

daemon/logs.go

@@ -25,6 +25,7 @@ type ContainerLogsConfig struct {
 	Since                time.Time
 	UseStdout, UseStderr bool
 	OutStream            io.Writer
+	Stop                 <-chan bool
 }
 
 func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) error {
@@ -119,7 +120,8 @@ func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) er
 	}
 
 	if config.Follow && container.IsRunning() {
-		chErr := make(chan error)
+		chErrStderr := make(chan error)
+		chErrStdout := make(chan error)
 		var stdoutPipe, stderrPipe io.ReadCloser
 
 		// write an empty chunk of data (this is to ensure that the
@@ -131,7 +133,7 @@ func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) er
 			stdoutPipe = container.StdoutLogPipe()
 			go func() {
 				logrus.Debug("logs: stdout stream begin")
-				chErr <- jsonlog.WriteLog(stdoutPipe, outStream, format, config.Since)
+				chErrStdout <- jsonlog.WriteLog(stdoutPipe, outStream, format, config.Since)
 				logrus.Debug("logs: stdout stream end")
 			}()
 		}
@@ -139,19 +141,33 @@ func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) er
 			stderrPipe = container.StderrLogPipe()
 			go func() {
 				logrus.Debug("logs: stderr stream begin")
-				chErr <- jsonlog.WriteLog(stderrPipe, errStream, format, config.Since)
+				chErrStderr <- jsonlog.WriteLog(stderrPipe, errStream, format, config.Since)
 				logrus.Debug("logs: stderr stream end")
 			}()
 		}
 
-		err = <-chErr
+		select {
-		if stdoutPipe != nil {
+		case err = <-chErrStderr:
-			stdoutPipe.Close()
+			if stdoutPipe != nil {
+				stdoutPipe.Close()
+				<-chErrStdout
+			}
+		case err = <-chErrStdout:
+			if stderrPipe != nil {
+				stderrPipe.Close()
+				<-chErrStderr
+			}
+		case <-config.Stop:
+			if stdoutPipe != nil {
+				stdoutPipe.Close()
+				<-chErrStdout
+			}
+			if stderrPipe != nil {
+				stderrPipe.Close()
+				<-chErrStderr
+			}
+			return nil
 		}
-		if stderrPipe != nil {
-			stderrPipe.Close()
-		}
-		<-chErr // wait for 2nd goroutine to exit, otherwise bad things will happen
 
 		if err != nil && err != io.EOF && err != io.ErrClosedPipe {
 			if e, ok := err.(*net.OpError); ok && e.Err != syscall.EPIPE {

integration-cli/docker_cli_logs_test.go

@@ -425,3 +425,44 @@ func (s *DockerSuite) TestLogsFollowGoroutinesWithStdout(c *check.C) {
 		}
 	}
 }
+
+func (s *DockerSuite) TestLogsFollowGoroutinesNoOutput(c *check.C) {
+	out, _ := dockerCmd(c, "run", "-d", "busybox", "/bin/sh", "-c", "while true; do sleep 2; done")
+	id := strings.TrimSpace(out)
+	c.Assert(waitRun(id), check.IsNil)
+
+	type info struct {
+		NGoroutines int
+	}
+	getNGoroutines := func() int {
+		var i info
+		status, b, err := sockRequest("GET", "/info", nil)
+		c.Assert(err, check.IsNil)
+		c.Assert(status, check.Equals, 200)
+		c.Assert(json.Unmarshal(b, &i), check.IsNil)
+		return i.NGoroutines
+	}
+
+	nroutines := getNGoroutines()
+
+	cmd := exec.Command(dockerBinary, "logs", "-f", id)
+	c.Assert(cmd.Start(), check.IsNil)
+	time.Sleep(200 * time.Millisecond)
+	c.Assert(cmd.Process.Kill(), check.IsNil)
+
+	// NGoroutines is not updated right away, so we need to wait before failing
+	t := time.After(30 * time.Second)
+	for {
+		select {
+		case <-t:
+			if n := getNGoroutines(); n > nroutines {
+				c.Fatalf("leaked goroutines: expected less than or equal to %d, got: %d", nroutines, n)
+			}
+		default:
+			if n := getNGoroutines(); n <= nroutines {
+				return
+			}
+			time.Sleep(200 * time.Millisecond)
+		}
+	}
+}