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add comment describing the race condition + TODO for appropriate test

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This commit is contained in:
Uwe Krueger 2021-03-05 17:14:19 +01:00
parent d8ee8e427e
commit 932f98acaf
1 changed files with 12 additions and 0 deletions
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12
staging/src/k8s.io/apimachinery/pkg/watch/streamwatcher.go
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@ -124,6 +124,18 @@ func (sw *StreamWatcher) receive() {
klog.V(5).Infof("Unable to decode an event from the watch stream: %v", err) klog.V(5).Infof("Unable to decode an event from the watch stream: %v", err)
} else { } else {
select { select {
// TODO: figure out how to test that sending the error after an externally stopped watcher
// cannot block anymore because of the introduced done channel.
// The function receive checks under a lock whether the watch has been stopped,
// before an error from the watch stream is reported to the result channel.
// The problem here is, that in between the watcher might be stopped by
// calling the Stop method. In the actual code this is done by the
// cache.Reflector using the streamwatcher by a defer (method watchHandler)
// which is executed after the caller already stopped reading from the result channel.
// As a result the stopping flag might be set after the check
// and trying to send the error event blocks this send operation forever,
// because there will never be a receiver again.
// This results in dead go routines trying to send on the result channel, forever.
case <-sw.done: case <-sw.done:
return return
case sw.result <- Event{ case sw.result <- Event{