Split httpWatcher into watch.StreamWatcher and tools.APIEventDecoder.

pkg/watch/iowatcher.go

@@ -0,0 +1,91 @@
+/*
+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 watch
+
+import (
+	"sync"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
+)
+
+// Decoder allows StreamWatcher to watch any stream for which a Decoder can be written.
+type Decoder interface {
+	// Decode should return the type of event, the decoded object, or an error.
+	// An error will cause StreamWatcher to call Close(). Decode should block until
+	// it has data or an error occurs.
+	Decode() (action EventType, object interface{}, err error)
+
+	// Close should close the underlying io.Reader, signalling to the source of
+	// the stream that it is no longer being watched. Close() must cause any
+	// outstanding call to Decode() to return with an error of some sort.
+	Close()
+}
+
+// StreamWatcher turns any stream for which you can write a Decoder interface
+// into a watch.Interface.
+type StreamWatcher struct {
+	source Decoder
+	result chan Event
+	sync.Mutex
+	stopped bool
+}
+
+// NewStreamWatcher creates a StreamWatcher from the given decoder.
+func NewStreamWatcher(d Decoder) *StreamWatcher {
+	sw := &StreamWatcher{
+		source: d,
+		// It's easy for a consumer to add buffering via an extra
+		// goroutine/channel, but impossible for them to remove it,
+		// so nonbuffered is better.
+		result: make(chan Event),
+	}
+	go sw.receive()
+	return sw
+}
+
+// ResultChan implements Interface.
+func (sw *StreamWatcher) ResultChan() <-chan Event {
+	return sw.result
+}
+
+// Stop implements Interface.
+func (sw *StreamWatcher) Stop() {
+	// Call Close() exactly once by locking and setting a flag.
+	sw.Lock()
+	defer sw.Unlock()
+	if !sw.stopped {
+		sw.stopped = true
+		sw.source.Close()
+	}
+}
+
+// In a loop, read a result from the decoder and send down the result channel.
+func (sw *StreamWatcher) receive() {
+	defer close(sw.result)
+	defer sw.Stop()
+	defer util.HandleCrash()
+	for {
+		action, obj, err := sw.source.Decode()
+		if err != nil {
+			return
+		}
+		sw.result <- Event{
+			Type:   action,
+			Object: obj,
+		}
+	}
+}

pkg/watch/iowatcher_test.go

@@ -0,0 +1,65 @@
+/*
+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 watch
+
+import (
+	"io"
+	"reflect"
+	"testing"
+)
+
+type fakeDecoder struct {
+	items chan Event
+}
+
+func (f fakeDecoder) Decode() (action EventType, object interface{}, err error) {
+	item, open := <-f.items
+	if !open {
+		return action, nil, io.EOF
+	}
+	return item.Type, item.Object, nil
+}
+
+func (f fakeDecoder) Close() {
+	close(f.items)
+}
+
+func TestStreamWatcher(t *testing.T) {
+	table := []Event{
+		{Added, "foo"},
+	}
+
+	fd := fakeDecoder{make(chan Event, 5)}
+	sw := NewStreamWatcher(fd)
+
+	for _, item := range table {
+		fd.items <- item
+		got, open := <-sw.ResultChan()
+		if !open {
+			t.Errorf("unexpected early close")
+		}
+		if e, a := item, got; !reflect.DeepEqual(e, a) {
+			t.Errorf("expected %v, got %v", e, a)
+		}
+	}
+
+	sw.Stop()
+	_, open := <-sw.ResultChan()
+	if open {
+		t.Errorf("Unexpected failure to close")
+	}
+}