Make sure log pipes are closed

Pipes are still not closed (and goroutines leaked) if neither pipe is
used.

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

daemon/logs.go

@@ -5,9 +5,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
 	"os"
 	"strconv"
-	"sync"
+	"syscall"
 	"time"
 
 	"github.com/Sirupsen/logrus"
@@ -132,9 +133,10 @@ func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) er
 			}
 		}
 	}
+
 	if config.Follow && container.IsRunning() {
-		errors := make(chan error, 2)
-		wg := sync.WaitGroup{}
+		chErr := make(chan error)
+		var stdoutPipe, stderrPipe io.ReadCloser
 
 		// write an empty chunk of data (this is to ensure that the
 		// HTTP Response is sent immediatly, even if the container has
@@ -142,33 +144,36 @@ func (daemon *Daemon) ContainerLogs(name string, config *ContainerLogsConfig) er
 		outStream.Write(nil)
 
 		if config.UseStdout {
-			wg.Add(1)
-			stdoutPipe := container.StdoutLogPipe()
-			defer stdoutPipe.Close()
+			stdoutPipe = container.StdoutLogPipe()
 			go func() {
-				errors <- jsonlog.WriteLog(stdoutPipe, outStream, format, config.Since)
-				wg.Done()
+				logrus.Debug("logs: stdout stream begin")
+				chErr <- jsonlog.WriteLog(stdoutPipe, outStream, format, config.Since)
+				logrus.Debug("logs: stdout stream end")
 			}()
 		}
 		if config.UseStderr {
-			wg.Add(1)
-			stderrPipe := container.StderrLogPipe()
-			defer stderrPipe.Close()
+			stderrPipe = container.StderrLogPipe()
 			go func() {
-				errors <- jsonlog.WriteLog(stderrPipe, errStream, format, config.Since)
-				wg.Done()
+				logrus.Debug("logs: stderr stream begin")
+				chErr <- jsonlog.WriteLog(stderrPipe, errStream, format, config.Since)
+				logrus.Debug("logs: stderr stream end")
 			}()
 		}
 
-		wg.Wait()
-		close(errors)
+		err = <-chErr
+		if stdoutPipe != nil {
+			stdoutPipe.Close()
+		}
+		if stderrPipe != nil {
+			stderrPipe.Close()
+		}
+		<-chErr // wait for 2nd goroutine to exit, otherwise bad things will happen
 
-		for err := range errors {
-			if err != nil {
-				logrus.Errorf("%s", err)
+		if err != nil && err != io.EOF && err != io.ErrClosedPipe {
+			if e, ok := err.(*net.OpError); ok && e.Err != syscall.EPIPE {
+				logrus.Errorf("error streaming logs: %v", err)
 			}
 		}
-
 	}
 	return nil
 }

integration-cli/docker_cli_logs_test.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"encoding/json"
 	"fmt"
+	"io"
 	"os/exec"
 	"regexp"
 	"strconv"
@@ -393,3 +395,52 @@ func (s *DockerSuite) TestLogsFollowSlowStdoutConsumer(c *check.C) {
 	}
 
 }
+
+func (s *DockerSuite) TestLogsFollowGoroutinesWithStdout(c *check.C) {
+	out, _ := dockerCmd(c, "run", "-d", "busybox", "/bin/sh", "-c", "while true; do echo hello; 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)
+	r, w := io.Pipe()
+	cmd.Stdout = w
+	c.Assert(cmd.Start(), check.IsNil)
+
+	// Make sure pipe is written to
+	chErr := make(chan error)
+	go func() {
+		b := make([]byte, 1)
+		_, err := r.Read(b)
+		chErr <- err
+	}()
+	c.Assert(<-chErr, check.IsNil)
+	c.Assert(cmd.Process.Kill(), check.IsNil)
+
+	// NGoroutines is not updated right away, so we need to wait before failing
+	t := time.After(5 * time.Second)
+	for {
+		select {
+		case <-t:
+			c.Assert(nroutines, check.Equals, getNGoroutines())
+		default:
+			if nroutines == getNGoroutines() {
+				return
+			}
+			time.Sleep(100 * time.Millisecond)
+		}
+	}
+}

pkg/jsonlog/jsonlog.go

@@ -5,8 +5,6 @@ import (
 	"fmt"
 	"io"
 	"time"
-
-	"github.com/Sirupsen/logrus"
 )
 
 type JSONLog struct {
@@ -37,15 +35,16 @@ func WriteLog(src io.Reader, dst io.Writer, format string, since time.Time) erro
 	l := &JSONLog{}
 	for {
 		l.Reset()
-		if err := dec.Decode(l); err == io.EOF {
+		if err := dec.Decode(l); err != nil {
+			if err == io.EOF {
 				return nil
-		} else if err != nil {
-			logrus.Printf("Error streaming logs: %s", err)
+			}
 			return err
 		}
 		if !since.IsZero() && l.Created.Before(since) {
 			continue
 		}
+
 		line, err := l.Format(format)
 		if err != nil {
 			return err