Move flushwriter from Kubelet server to a common util package

Exposes a Wrap function to wrap a given writer into a writer that
flushes with every write if the writer also implements the io.Flusher
interface.

pkg/kubelet/handlers.go

@@ -18,9 +18,7 @@ package kubelet
 
 import (
 	"fmt"
-	"io"
 	"net"
-	"net/http"
 	"strconv"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
@@ -95,21 +93,3 @@ func (h *httpActionHandler) Run(podFullName string, uid types.UID, container *ap
 	_, err := h.client.Get(url)
 	return err
 }
-
-// FlushWriter provides wrapper for responseWriter with HTTP streaming capabilities
-type FlushWriter struct {
-	flusher http.Flusher
-	writer  io.Writer
-}
-
-// Write is a FlushWriter implementation of the io.Writer that sends any buffered data to the client.
-func (fw *FlushWriter) Write(p []byte) (n int, err error) {
-	n, err = fw.writer.Write(p)
-	if err != nil {
-		return
-	}
-	if fw.flusher != nil {
-		fw.flusher.Flush()
-	}
-	return
-}

pkg/kubelet/server.go

@@ -38,6 +38,7 @@ import (
 	kubecontainer "github.com/GoogleCloudPlatform/kubernetes/pkg/kubelet/container"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/types"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util/flushwriter"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/util/httpstream"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/util/httpstream/spdy"
 	"github.com/golang/glog"
@@ -262,15 +263,14 @@ func (s *Server) handleContainerLogs(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	fw := FlushWriter{writer: w}
-	if flusher, ok := fw.writer.(http.Flusher); ok {
-		fw.flusher = flusher
-	} else {
-		s.error(w, fmt.Errorf("unable to convert %v into http.Flusher", fw))
+	if _, ok := w.(http.Flusher); !ok {
+		s.error(w, fmt.Errorf("unable to convert %v into http.Flusher", w))
+		return
 	}
+	fw := flushwriter.Wrap(w)
 	w.Header().Set("Transfer-Encoding", "chunked")
 	w.WriteHeader(http.StatusOK)
-	err = s.host.GetKubeletContainerLogs(kubecontainer.GetPodFullName(pod), containerName, tail, follow, &fw, &fw)
+	err = s.host.GetKubeletContainerLogs(kubecontainer.GetPodFullName(pod), containerName, tail, follow, fw, fw)
 	if err != nil {
 		s.error(w, err)
 		return

pkg/util/flushwriter/doc.go

@@ -0,0 +1,19 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package flushwriter implements a wrapper for a writer that flushes on every
+// write if that writer implements the io.Flusher interface
+package flushwriter

pkg/util/flushwriter/writer.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flushwriter
+
+import (
+	"io"
+	"net/http"
+)
+
+// Wrap wraps an io.Writer into a writer that flushes after every write if
+// the writer implements the Flusher interface.
+func Wrap(w io.Writer) io.Writer {
+	fw := &flushWriter{
+		writer: w,
+	}
+	if flusher, ok := w.(http.Flusher); ok {
+		fw.flusher = flusher
+	}
+	return fw
+}
+
+// flushWriter provides wrapper for responseWriter with HTTP streaming capabilities
+type flushWriter struct {
+	flusher http.Flusher
+	writer  io.Writer
+}
+
+// Write is a FlushWriter implementation of the io.Writer that sends any buffered
+// data to the client.
+func (fw *flushWriter) Write(p []byte) (n int, err error) {
+	n, err = fw.writer.Write(p)
+	if err != nil {
+		return
+	}
+	if fw.flusher != nil {
+		fw.flusher.Flush()
+	}
+	return
+}

pkg/util/flushwriter/writer_test.go

@@ -0,0 +1,86 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flushwriter
+
+import (
+	"fmt"
+	"testing"
+)
+
+type writerWithFlush struct {
+	writeCount, flushCount int
+	err                    error
+}
+
+func (w *writerWithFlush) Flush() {
+	w.flushCount++
+}
+
+func (w *writerWithFlush) Write(p []byte) (n int, err error) {
+	w.writeCount++
+	return len(p), w.err
+}
+
+type writerWithNoFlush struct {
+	writeCount int
+}
+
+func (w *writerWithNoFlush) Write(p []byte) (n int, err error) {
+	w.writeCount++
+	return len(p), nil
+}
+
+func TestWriteWithFlush(t *testing.T) {
+	w := &writerWithFlush{}
+	fw := Wrap(w)
+	for i := 0; i < 10; i++ {
+		_, err := fw.Write([]byte("Test write"))
+		if err != nil {
+			t.Errorf("Unexpected error while writing with flush writer: %v", err)
+		}
+	}
+	if w.flushCount != 10 {
+		t.Errorf("Flush not called the expected number of times. Actual: %d", w.flushCount)
+	}
+	if w.writeCount != 10 {
+		t.Errorf("Write not called the expected number of times. Actual: %d", w.writeCount)
+	}
+}
+
+func TestWriteWithoutFlush(t *testing.T) {
+	w := &writerWithNoFlush{}
+	fw := Wrap(w)
+	for i := 0; i < 10; i++ {
+		_, err := fw.Write([]byte("Test write"))
+		if err != nil {
+			t.Errorf("Unexpected error while writing with flush writer: %v", err)
+		}
+	}
+	if w.writeCount != 10 {
+		t.Errorf("Write not called the expected number of times. Actual: %d", w.writeCount)
+	}
+}
+
+func TestWriteError(t *testing.T) {
+	e := fmt.Errorf("Error")
+	w := &writerWithFlush{err: e}
+	fw := Wrap(w)
+	_, err := fw.Write([]byte("Test write"))
+	if err != e {
+		t.Errorf("Did not get expected error. Got: %#v", err)
+	}
+}