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Merge pull request #72364 from kdada/master

WaitFor returns immediately when done is closed
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k8s-ci-robot committed Jan 11, 2019
2 parents d6b0863 + 44b2e84 commit dd99c2ba7957269cb579f733b69cef4d3d9b1d30
@@ -856,7 +856,16 @@ func TestGarbageCollectorSync(t *testing.T) {
stopCh := make(chan struct{})
defer close(stopCh)
go gc.Run(1, stopCh)
go gc.Sync(fakeDiscoveryClient, 10*time.Millisecond, stopCh)
// The pseudo-code of GarbageCollector.Sync():
// GarbageCollector.Sync(client, period, stopCh):
// wait.Until() loops with `period` until the `stopCh` is closed :
// wait.PollImmediateUntil() loops with 100ms (hardcode) util the `stopCh` is closed:
// GetDeletableResources()
// gc.resyncMonitors()
// controller.WaitForCacheSync() loops with `syncedPollPeriod` (hardcoded to 100ms), until either its stop channel is closed after `period`, or all caches synced.
//
// Setting the period to 200ms allows the WaitForCacheSync() to check for cache sync ~2 times in every wait.PollImmediateUntil() loop.
go gc.Sync(fakeDiscoveryClient, 200*time.Millisecond, stopCh)

// Wait until the sync discovers the initial resources
fmt.Printf("Test output")
@@ -351,22 +351,21 @@ type WaitFunc func(done <-chan struct{}) <-chan struct{}
// WaitFor continually checks 'fn' as driven by 'wait'.
//
// WaitFor gets a channel from 'wait()'', and then invokes 'fn' once for every value
// placed on the channel and once more when the channel is closed.
// placed on the channel and once more when the channel is closed. If the channel is closed
// and 'fn' returns false without error, WaitFor returns ErrWaitTimeout.
//
// If 'fn' returns an error the loop ends and that error is returned, and if
// If 'fn' returns an error the loop ends and that error is returned. If
// 'fn' returns true the loop ends and nil is returned.
//
// ErrWaitTimeout will be returned if the channel is closed without fn ever
// ErrWaitTimeout will be returned if the 'done' channel is closed without fn ever
// returning true.
//
// When the done channel is closed, because the golang `select` statement is
// "uniform pseudo-random", the `fn` might still run one or multiple time,
// though eventually `WaitFor` will return.
func WaitFor(wait WaitFunc, fn ConditionFunc, done <-chan struct{}) error {
stopCh := make(chan struct{})
once := sync.Once{}
closeCh := func() {
once.Do(func() {
close(stopCh)
})
}
defer closeCh()
defer close(stopCh)
c := wait(stopCh)
for {
select {
@@ -382,10 +381,9 @@ func WaitFor(wait WaitFunc, fn ConditionFunc, done <-chan struct{}) error {
return ErrWaitTimeout
}
case <-done:
closeCh()
return ErrWaitTimeout
}
}
return ErrWaitTimeout
}

// poller returns a WaitFunc that will send to the channel every interval until
@@ -456,11 +456,42 @@ func TestWaitFor(t *testing.T) {
}
}

// TestWaitForWithEarlyClosingWaitFunc tests WaitFor when the WaitFunc closes its channel. The WaitFor should
// always return ErrWaitTimeout.
func TestWaitForWithEarlyClosingWaitFunc(t *testing.T) {
stopCh := make(chan struct{})
defer close(stopCh)

start := time.Now()
err := WaitFor(func(done <-chan struct{}) <-chan struct{} {
c := make(chan struct{})
close(c)
return c
}, func() (bool, error) {
return false, nil
}, stopCh)
duration := time.Now().Sub(start)

// The WaitFor should return immediately, so the duration is close to 0s.
if duration >= ForeverTestTimeout/2 {
t.Errorf("expected short timeout duration")
}
if err != ErrWaitTimeout {
t.Errorf("expected ErrWaitTimeout from WaitFunc")
}
}

// TestWaitForWithClosedChannel tests WaitFor when it receives a closed channel. The WaitFor should
// always return ErrWaitTimeout.
func TestWaitForWithClosedChannel(t *testing.T) {
stopCh := make(chan struct{})
close(stopCh)
c := make(chan struct{})
defer close(c)
start := time.Now()
err := WaitFor(poller(ForeverTestTimeout, ForeverTestTimeout), func() (bool, error) {
err := WaitFor(func(done <-chan struct{}) <-chan struct{} {
return c
}, func() (bool, error) {
return false, nil
}, stopCh)
duration := time.Now().Sub(start)

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