Merge pull request #14365 from ncdc/poll-immediately

Check the condition immediately in util.Wait funcs

pkg/util/wait/wait.go

@@ -44,8 +44,6 @@ type ConditionFunc func() (done bool, err error)
 // is reached. condition will always be invoked at least once but some intervals
 // may be missed if the condition takes too long or the time window is too short.
 // If you want to Poll something forever, see PollInfinite.
-// Poll always waits the interval before the first check of the condition.
-// TODO: create a separate PollImmediate function that does not wait.
 func Poll(interval, timeout time.Duration, condition ConditionFunc) error {
 	return WaitFor(poller(interval, timeout), condition)
 }
@@ -90,7 +88,12 @@ func WaitFor(wait WaitFunc, c ConditionFunc) error {
 func poller(interval, timeout time.Duration) WaitFunc {
 	return WaitFunc(func() <-chan struct{} {
 		ch := make(chan struct{})
+
 		go func() {
+			// send to the channel once immediately, rather than waiting for the first
+			// interval to elapse
+			ch <- struct{}{}
+
 			tick := time.NewTicker(interval)
 			defer tick.Stop()
 			var after <-chan time.Time

pkg/util/wait/wait_test.go

@@ -40,8 +40,8 @@ DRAIN:
 			t.Errorf("unexpected timeout after poll")
 		}
 	}
-	if count > 3 {
+	if count < 2 {
-		t.Errorf("expected up to three values, got %d", count)
+		t.Errorf("expected at least two values, got %d", count)
 	}
 }