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Merge pull request #98653 from mandelsoft/stream
fix race condition problem in streamwatcher
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commit
ab7d68a58a
@ -55,7 +55,7 @@ type StreamWatcher struct {
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source Decoder
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reporter Reporter
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result chan Event
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stopped bool
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done chan struct{}
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}
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// NewStreamWatcher creates a StreamWatcher from the given decoder.
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@ -67,6 +67,11 @@ func NewStreamWatcher(d Decoder, r Reporter) *StreamWatcher {
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// goroutine/channel, but impossible for them to remove it,
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// so nonbuffered is better.
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result: make(chan Event),
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// If the watcher is externally stopped there is no receiver anymore
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// and the send operations on the result channel, especially the
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// error reporting might block forever.
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// Therefore a dedicated stop channel is used to resolve this blocking.
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done: make(chan struct{}),
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}
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go sw.receive()
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return sw
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@ -82,19 +87,15 @@ func (sw *StreamWatcher) Stop() {
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// Call Close() exactly once by locking and setting a flag.
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sw.Lock()
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defer sw.Unlock()
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if !sw.stopped {
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sw.stopped = true
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// closing a closed channel always panics, therefore check before closing
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select {
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case <-sw.done:
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default:
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close(sw.done)
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sw.source.Close()
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}
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}
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// stopping returns true if Stop() was called previously.
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func (sw *StreamWatcher) stopping() bool {
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sw.Lock()
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defer sw.Unlock()
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return sw.stopped
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}
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// receive reads result from the decoder in a loop and sends down the result channel.
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func (sw *StreamWatcher) receive() {
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defer utilruntime.HandleCrash()
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@ -103,10 +104,6 @@ func (sw *StreamWatcher) receive() {
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for {
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action, obj, err := sw.source.Decode()
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if err != nil {
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// Ignore expected error.
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if sw.stopping() {
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return
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}
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switch err {
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case io.EOF:
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// watch closed normally
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@ -116,17 +113,24 @@ func (sw *StreamWatcher) receive() {
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if net.IsProbableEOF(err) || net.IsTimeout(err) {
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klog.V(5).Infof("Unable to decode an event from the watch stream: %v", err)
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} else {
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sw.result <- Event{
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select {
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case <-sw.done:
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case sw.result <- Event{
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Type: Error,
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Object: sw.reporter.AsObject(fmt.Errorf("unable to decode an event from the watch stream: %v", err)),
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}:
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}
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}
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}
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return
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}
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sw.result <- Event{
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select {
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case <-sw.done:
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return
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case sw.result <- Event{
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Type: action,
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Object: obj,
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}:
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}
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}
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}
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@ -21,6 +21,7 @@ import (
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"io"
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"reflect"
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"testing"
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"time"
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"k8s.io/apimachinery/pkg/runtime"
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. "k8s.io/apimachinery/pkg/watch"
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@ -105,3 +106,16 @@ func TestStreamWatcherError(t *testing.T) {
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t.Fatalf("unexpected open channel")
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}
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}
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func TestStreamWatcherRace(t *testing.T) {
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fd := fakeDecoder{err: fmt.Errorf("test error")}
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fr := &fakeReporter{}
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sw := NewStreamWatcher(fd, fr)
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time.Sleep(10 * time.Millisecond)
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sw.Stop()
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time.Sleep(10 * time.Millisecond)
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_, ok := <-sw.ResultChan()
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if ok {
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t.Fatalf("unexpected pending send")
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}
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}
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