BroadcastWriter refactoring

It became slightly faster and lighter
possibly fixes #5923 problems

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)

daemon/container.go

@@ -503,10 +503,10 @@ func (container *Container) cleanup() {
 			utils.Errorf("%s: Error close stdin: %s", container.ID, err)
 		}
 	}
-	if err := container.stdout.Close(); err != nil {
+	if err := container.stdout.Clean(); err != nil {
 		utils.Errorf("%s: Error close stdout: %s", container.ID, err)
 	}
-	if err := container.stderr.Close(); err != nil {
+	if err := container.stderr.Clean(); err != nil {
 		utils.Errorf("%s: Error close stderr: %s", container.ID, err)
 	}
 	if container.command != nil && container.command.Terminal != nil {

utils/broadcastwriter/broadcastwriter.go

@@ -10,12 +10,16 @@ import (
 	"github.com/dotcloud/docker/utils"
 )
 
+// BroadcastWriter accumulate multiple io.WriteCloser by stream.
 type BroadcastWriter struct {
 	sync.Mutex
 	buf     *bytes.Buffer
 	streams map[string](map[io.WriteCloser]struct{})
 }
 
+// AddWriter adds new io.WriteCloser for stream.
+// If stream is "", then all writes proceed as is. Otherwise every line from
+// input will be packed to serialized utils.JSONLog.
 func (w *BroadcastWriter) AddWriter(writer io.WriteCloser, stream string) {
 	w.Lock()
 	if _, ok := w.streams[stream]; !ok {
@@ -25,10 +29,11 @@ func (w *BroadcastWriter) AddWriter(writer io.WriteCloser, stream string) {
 	w.Unlock()
 }
 
+// Write writes bytes to all writers. Failed writers will be evicted during
+// this call.
 func (w *BroadcastWriter) Write(p []byte) (n int, err error) {
 	created := time.Now().UTC()
 	w.Lock()
-	defer w.Unlock()
 	if writers, ok := w.streams[""]; ok {
 		for sw := range writers {
 			if n, err := sw.Write(p); err != nil || n != len(p) {
@@ -38,49 +43,44 @@ func (w *BroadcastWriter) Write(p []byte) (n int, err error) {
 		}
 	}
 	w.buf.Write(p)
-	lines := []string{}
 	for {
 		line, err := w.buf.ReadString('\n')
 		if err != nil {
 			w.buf.Write([]byte(line))
 			break
 		}
-		lines = append(lines, line)
-	}
-
-	if len(lines) != 0 {
 		for stream, writers := range w.streams {
 			if stream == "" {
 				continue
 			}
-			var lp []byte
-			for _, line := range lines {
-				b, err := json.Marshal(&utils.JSONLog{Log: line, Stream: stream, Created: created})
-				if err != nil {
-					utils.Errorf("Error making JSON log line: %s", err)
-				}
-				lp = append(lp, b...)
-				lp = append(lp, '\n')
+			b, err := json.Marshal(utils.JSONLog{Log: line, Stream: stream, Created: created})
+			if err != nil {
+				utils.Errorf("Error making JSON log line: %s", err)
+				continue
 			}
+			b = append(b, '\n')
 			for sw := range writers {
-				if _, err := sw.Write(lp); err != nil {
+				if _, err := sw.Write(b); err != nil {
 					delete(writers, sw)
 				}
 			}
 		}
 	}
+	w.Unlock()
 	return len(p), nil
 }
 
-func (w *BroadcastWriter) Close() error {
+// Clean closes and removes all writers. Last non-eol-terminated part of data
+// will be saved.
+func (w *BroadcastWriter) Clean() error {
 	w.Lock()
-	defer w.Unlock()
 	for _, writers := range w.streams {
 		for w := range writers {
 			w.Close()
 		}
 	}
 	w.streams = make(map[string](map[io.WriteCloser]struct{}))
+	w.Unlock()
 	return nil
 }
 

utils/broadcastwriter/broadcastwriter_test.go

@@ -82,7 +82,7 @@ func TestBroadcastWriter(t *testing.T) {
 		t.Errorf("Buffer contains %v", bufferC.String())
 	}
 
-	writer.Close()
+	writer.Clean()
 }
 
 type devNullCloser int
@@ -138,7 +138,7 @@ func BenchmarkBroadcastWriter(b *testing.B) {
 		}
 
 		b.StopTimer()
-		writer.Close()
+		writer.Clean()
 		b.StartTimer()
 	}
 }