Update logger adapter test to avoid race

Add synchronization around adding logs to a plugin
and reading those logs. Without the follow configuration,
a race occurs between go routines to add the logs into
the plugin and read the logs out of the plugin. This
adds a function to synchronize the action to avoid the
race.
Removes use of file for buffering, instead buffering whole
messages so log count can be checked discretely.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/logger/adapter_test.go

@@ -3,8 +3,7 @@ package logger // import "github.com/docker/docker/daemon/logger"
 import (
 	"encoding/binary"
 	"io"
-	"io/ioutil"
-	"os"
+	"sync"
 	"testing"
 	"time"
 
@@ -17,24 +16,57 @@ import (
 // mockLoggingPlugin implements the loggingPlugin interface for testing purposes
 // it only supports a single log stream
 type mockLoggingPlugin struct {
-	inStream io.ReadCloser
-	f        *os.File
-	closed   chan struct{}
-	t        *testing.T
+	io.WriteCloser
+	inStream io.Reader
+	logs     []*logdriver.LogEntry
+	c        *sync.Cond
+	err      error
+}
+
+func newMockLoggingPlugin() *mockLoggingPlugin {
+	r, w := io.Pipe()
+	return &mockLoggingPlugin{
+		WriteCloser: w,
+		inStream:    r,
+		logs:        []*logdriver.LogEntry{},
+		c:           sync.NewCond(new(sync.Mutex)),
+	}
 }
 
 func (l *mockLoggingPlugin) StartLogging(file string, info Info) error {
 	go func() {
-		io.Copy(l.f, l.inStream)
-		close(l.closed)
+		dec := protoio.NewUint32DelimitedReader(l.inStream, binary.BigEndian, 1e6)
+		for {
+			var msg logdriver.LogEntry
+			if err := dec.ReadMsg(&msg); err != nil {
+				l.c.L.Lock()
+				if l.err == nil {
+					l.err = err
+				}
+				l.c.L.Unlock()
+
+				l.c.Broadcast()
+				return
+
+			}
+
+			l.c.L.Lock()
+			l.logs = append(l.logs, &msg)
+			l.c.L.Unlock()
+			l.c.Broadcast()
+		}
+
 	}()
 	return nil
 }
 
 func (l *mockLoggingPlugin) StopLogging(file string) error {
-	l.inStream.Close()
-	l.f.Close()
-	os.Remove(l.f.Name())
+	l.c.L.Lock()
+	if l.err == nil {
+		l.err = io.EOF
+	}
+	l.c.L.Unlock()
+	l.c.Broadcast()
 	return nil
 }
 
@@ -44,63 +76,60 @@ func (l *mockLoggingPlugin) Capabilities() (cap Capability, err error) {
 
 func (l *mockLoggingPlugin) ReadLogs(info Info, config ReadConfig) (io.ReadCloser, error) {
 	r, w := io.Pipe()
-	f, err := os.Open(l.f.Name())
-	if err != nil {
-		return nil, err
-	}
+
 	go func() {
-		defer f.Close()
-		dec := protoio.NewUint32DelimitedReader(f, binary.BigEndian, 1e6)
+		var idx int
 		enc := logdriver.NewLogEntryEncoder(w)
 
+		l.c.L.Lock()
+		defer l.c.L.Unlock()
 		for {
-			select {
-			case <-l.closed:
+			if l.err != nil {
 				w.Close()
 				return
-			default:
 			}
 
-			var msg logdriver.LogEntry
-			if err := dec.ReadMsg(&msg); err != nil {
-				if err == io.EOF {
-					if !config.Follow {
-						w.Close()
-						return
-					}
-					dec = protoio.NewUint32DelimitedReader(f, binary.BigEndian, 1e6)
-					continue
+			if idx >= len(l.logs) {
+				if !config.Follow {
+					w.Close()
+					return
 				}
 
-				l.t.Fatal(err)
+				l.c.Wait()
 				continue
 			}
 
-			if err := enc.Encode(&msg); err != nil {
+			if err := enc.Encode(l.logs[idx]); err != nil {
 				w.CloseWithError(err)
 				return
 			}
+			idx++
 		}
 	}()
 
 	return r, nil
 }
 
-func newMockPluginAdapter(t *testing.T) Logger {
-	r, w := io.Pipe()
-	f, err := ioutil.TempFile("", "mock-plugin-adapter")
-	assert.Check(t, err)
+func (l *mockLoggingPlugin) waitLen(i int) {
+	l.c.L.Lock()
+	defer l.c.L.Unlock()
+	for len(l.logs) < i {
+		l.c.Wait()
+	}
+}
 
-	enc := logdriver.NewLogEntryEncoder(w)
+func (l *mockLoggingPlugin) check(t *testing.T) {
+	if l.err != nil && l.err != io.EOF {
+		t.Fatal(l.err)
+	}
+}
+
+func newMockPluginAdapter(plugin *mockLoggingPlugin) Logger {
+	enc := logdriver.NewLogEntryEncoder(plugin)
 	a := &pluginAdapterWithRead{
 		&pluginAdapter{
-			plugin: &mockLoggingPlugin{
-				inStream: r,
-				f:        f,
-				closed:   make(chan struct{}),
-				t:        t,
-			},
-			stream: w,
+			plugin: plugin,
+			stream: plugin,
 			enc:    enc,
 		},
 	}
@@ -109,7 +138,8 @@ func newMockPluginAdapter(t *testing.T) Logger {
 }
 
 func TestAdapterReadLogs(t *testing.T) {
-	l := newMockPluginAdapter(t)
+	plugin := newMockLoggingPlugin()
+	l := newMockPluginAdapter(plugin)
 
 	testMsg := []Message{
 		{Line: []byte("Are you the keymaker?"), Timestamp: time.Now()},
@@ -120,6 +150,9 @@ func TestAdapterReadLogs(t *testing.T) {
 		assert.Check(t, l.Log(m))
 	}
 
+	// Wait until messages are read into plugin
+	plugin.waitLen(len(testMsg))
+
 	lr, ok := l.(LogReader)
 	assert.Check(t, ok, "Logger does not implement LogReader")
 
@@ -172,6 +205,8 @@ func TestAdapterReadLogs(t *testing.T) {
 	case <-time.After(10 * time.Second):
 		t.Fatal("timeout waiting for logger to close")
 	}
+
+	plugin.check(t)
 }
 
 func testMessageEqual(t *testing.T, a, b *Message) {