rkhachatryan commented on a change in pull request #10151: [FLINK-14231] Handle
the processing-time timers when closing operators to make endInput semantics on
the operator chain strict
URL: https://github.com/apache/flink/pull/10151#discussion_r355457319
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/ProcessingTimeServiceImpl.java
##########
@@ -39,11 +78,282 @@ public long getCurrentProcessingTime() {
@Override
public ScheduledFuture<?> registerTimer(long timestamp,
ProcessingTimeCallback target) {
- return timerService.registerTimer(timestamp,
processingTimeCallbackWrapper.apply(target));
+ if (isQuiesced()) {
+ return new NeverCompleteFuture(
+
ProcessingTimeServiceUtil.getProcessingTimeDelay(timestamp,
getCurrentProcessingTime()));
+ }
+
+ final TimerScheduledFuture<?> timer = new
TimerScheduledFuture<Void>(false, this::removeUndoneTimer);
+ undoneTimers.put(timer, Boolean.TRUE);
+
+ // double check to deal with the following race conditions:
+ // 1. canceling timers from the undone table occurs before
putting this timer into the undone table
+ // (see #cancelTimersNotInExecuting())
+ // 2. using the size of the undone table to determine if all
timers have done occurs before putting
+ // this timer into the undone table (see
#tryCompleteTimersDoneFutureIfQuiesced())
+ if (isQuiesced()) {
+ removeUndoneTimer(timer);
+ return new NeverCompleteFuture(
+
ProcessingTimeServiceUtil.getProcessingTimeDelay(timestamp,
getCurrentProcessingTime()));
+ }
+
+ timer.bind(timerService.registerTimer(timestamp,
timer.getCallback(processingTimeCallbackWrapper.apply(target))));
+
+ return timer;
}
@Override
public ScheduledFuture<?> scheduleAtFixedRate(ProcessingTimeCallback
callback, long initialDelay, long period) {
- return
timerService.scheduleAtFixedRate(processingTimeCallbackWrapper.apply(callback),
initialDelay, period);
+ if (isQuiesced()) {
+ return new NeverCompleteFuture(initialDelay);
+ }
+
+ final TimerScheduledFuture<?> timer = new
TimerScheduledFuture<Void>(true, this::removeUndoneTimer);
+ undoneTimers.put(timer, Boolean.TRUE);
+
+ // double check to deal with the following race conditions:
+ // 1. canceling timers from the undone table occurs before
putting this timer into the undone table
+ // (see #cancelTimersNotInExecuting())
+ // 2. using the size of the undone table to determine if all
timers have done occurs before putting
+ // this timer into the undone table (see
#tryCompleteTimersDoneFutureIfQuiesced())
+ if (isQuiesced()) {
+ removeUndoneTimer(timer);
+ return new NeverCompleteFuture(initialDelay);
+ }
+
+ timer.bind(
+ timerService.scheduleAtFixedRate(
+
timer.getCallback(processingTimeCallbackWrapper.apply(callback)), initialDelay,
period));
+
+ return timer;
+ }
+
+ void quiesce() {
+ status.compareAndSet(STATUS_ALIVE, STATUS_QUIESCED);
+ }
+
+ /**
+ * This is an idempotent method to allow to repeatedly call.
+ */
+ CompletableFuture<Void> cancelTimersGracefullyAfterQuiesce() {
+ checkState(status.get() == STATUS_QUIESCED);
+
+ if (!timersDoneFutureAfterQuiescing.isDone()) {
+ if (!cancelTimersNotInExecuting()) {
+ return FutureUtils.completedExceptionally(new
CancellationException("Cancel timers failed"));
+ }
+ tryCompleteTimersDoneFutureIfQuiesced();
+ }
+
+ return timersDoneFutureAfterQuiescing;
+ }
+
+ @VisibleForTesting
+ int getNumUndoneTimers() {
+ return undoneTimers.size();
+ }
+
+ private boolean isQuiesced() {
+ return status.get() == STATUS_QUIESCED;
+ }
+
+ private void removeUndoneTimer(TimerScheduledFuture<?> timer) {
+ undoneTimers.remove(timer);
+ tryCompleteTimersDoneFutureIfQuiesced();
+ }
+
+ private void tryCompleteTimersDoneFutureIfQuiesced() {
+ if (isQuiesced() && getNumUndoneTimers() == 0) {
+ timersDoneFutureAfterQuiescing.complete(null);
+ }
+ }
+
+ private boolean cancelTimersNotInExecuting() {
+ // we should cancel the timers in descending timestamp order
+ TimerScheduledFuture<?>[] timers =
undoneTimers.keySet().toArray(new TimerScheduledFuture<?>[0]);
+ Arrays.sort(timers, Comparator.reverseOrder());
+ for (TimerScheduledFuture<?> timer : timers) {
+ if (!timer.cancel(false) &&
!timer.canDoneIfCancellationFailure()) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ static final class TimerScheduledFuture<V> implements
ScheduledFuture<V> {
Review comment:
The logic with status switching seems overcomplicated, and the class only
purpose to just call `removeUndoneTimer` once wrapped future canceled
successfully or completed after cancellation.
Can't this be simplified using `CompletableFuture`?
Something like this:
```
private Set<CompletableFuture<?>> pending = ...
public ScheduledFuture<?> registerTimer(long timestamp,
ProcessingTimeCallback target) {
CompletableFuture<Void> cf = new CompletableFuture<>();
timerService.registerTimer(timestamp, t -> {
try {
target.onProcessingTime(t);
cf.complete(null);
} catch (Exception e) {
cf.completeExceptionally(e);
}
});
pending.add(cf);
cf.whenComplete((unused1, unused2) -> removeUndoneTimer(timer));
}
CompletableFuture<Void> cancelTimersGracefullyAfterQuiesce() {
pending.forEach(p -> p.cancel(false));
return timersDoneFutureAfterQuiescing;
}
```
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