1u0 commented on a change in pull request #8523: [FLINK-12481][runtime] Invoke
timer callback in task thread (via mailbox)
URL: https://github.com/apache/flink/pull/8523#discussion_r288273753
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SystemProcessingTimeService.java
##########
@@ -253,89 +243,53 @@ int getNumTasksScheduled() {
//
------------------------------------------------------------------------
/**
- * Internal task that is invoked by the timer service and triggers the
target.
+ * A context to which {@link ProcessingTimeCallback} would be passed to
be invoked when a timer is up.
*/
- private static final class TriggerTask implements Runnable {
+ public interface ScheduledCallbackExecutionContext {
- private final AtomicInteger serviceStatus;
- private final Object lock;
- private final ProcessingTimeCallback target;
- private final long timestamp;
- private final AsyncExceptionHandler exceptionHandler;
-
- private TriggerTask(
- final AtomicInteger serviceStatus,
- final AsyncExceptionHandler exceptionHandler,
- final Object lock,
- final ProcessingTimeCallback target,
- final long timestamp) {
-
- this.serviceStatus =
Preconditions.checkNotNull(serviceStatus);
- this.exceptionHandler =
Preconditions.checkNotNull(exceptionHandler);
- this.lock = Preconditions.checkNotNull(lock);
- this.target = Preconditions.checkNotNull(target);
- this.timestamp = timestamp;
- }
+ void invoke(ProcessingTimeCallback callback, long timestamp)
throws InterruptedException;
+ }
- @Override
- public void run() {
- synchronized (lock) {
- try {
- if (serviceStatus.get() ==
STATUS_ALIVE) {
-
target.onProcessingTime(timestamp);
- }
- } catch (Throwable t) {
- TimerException asyncException = new
TimerException(t);
-
exceptionHandler.handleAsyncException("Caught exception while processing
timer.", asyncException);
- }
- }
- }
+ private Runnable wrapOnTimerCallback(ProcessingTimeCallback callback,
long timestamp) {
+ return new TimeTrackingDelegate(status,
callbackExecutionContext, callback, timestamp, 0);
}
- /**
- * Internal task which is repeatedly called by the processing time
service.
- */
- private static final class RepeatedTriggerTask implements Runnable {
+ private Runnable wrapOnTimerCallback(ProcessingTimeCallback callback,
long nextTimestamp, long period) {
+ return new TimeTrackingDelegate(status,
callbackExecutionContext, callback, nextTimestamp, period);
+ }
+ private static final class TimeTrackingDelegate implements Runnable {
private final AtomicInteger serviceStatus;
- private final Object lock;
- private final ProcessingTimeCallback target;
- private final long period;
- private final AsyncExceptionHandler exceptionHandler;
+ private final ScheduledCallbackExecutionContext
callbackExecutionContext;
+ private final ProcessingTimeCallback callback;
private long nextTimestamp;
+ private final long period;
- private RepeatedTriggerTask(
- final AtomicInteger serviceStatus,
- final AsyncExceptionHandler exceptionHandler,
- final Object lock,
- final ProcessingTimeCallback target,
- final long nextTimestamp,
- final long period) {
-
- this.serviceStatus =
Preconditions.checkNotNull(serviceStatus);
- this.lock = Preconditions.checkNotNull(lock);
- this.target = Preconditions.checkNotNull(target);
+ TimeTrackingDelegate(
+ AtomicInteger serviceStatus,
+ ScheduledCallbackExecutionContext
callbackExecutionContext,
+ ProcessingTimeCallback callback,
+ long timestamp,
+ long period) {
+ this.serviceStatus = serviceStatus;
+ this.callbackExecutionContext =
callbackExecutionContext;
+ this.callback = callback;
+ this.nextTimestamp = timestamp;
this.period = period;
- this.exceptionHandler =
Preconditions.checkNotNull(exceptionHandler);
-
- this.nextTimestamp = nextTimestamp;
}
@Override
public void run() {
- synchronized (lock) {
- try {
- if (serviceStatus.get() ==
STATUS_ALIVE) {
-
target.onProcessingTime(nextTimestamp);
- }
-
- nextTimestamp += period;
- } catch (Throwable t) {
- TimerException asyncException = new
TimerException(t);
-
exceptionHandler.handleAsyncException("Caught exception while processing
repeated timer task.", asyncException);
- }
+ if (serviceStatus.get() != STATUS_ALIVE) {
+ return;
+ }
+ try {
+ callbackExecutionContext.invoke(callback,
nextTimestamp);
+ } catch (InterruptedException ex) {
+ Thread.currentThread().interrupt();
Review comment:
(+ to the other your comment about `InterruptedException`)
Frankly, I also wonder how and where to handle this exception.
Same question applies for checkpoints handling in the main task thread
(FLINK-12482).
Some of my thoughts:
The root of this exception is in `ReentrantLock.lockInterruptibly()` used in
the mailbox.
If the exception is actually thrown, I interpret it that the mailbox queue
is full (the sender thread had to sleep, assumption that the threads in the
time service thread pool don't have interrupted status set). So if something
external interrupts the time service thread on mailbox, I assume it's
somethings "disastrous", like forced shutdown of task manager.
Here, I handle the exception in the `SystemProcessingTimeService`, as the
thread belongs to the thread pool of this service. So the service may decide
what to do with such exception.
On the time service side, basically there is not much to do with it and the
thread actually was "told" to be interrupted. So for now, the
`Thread.currentThread().interrupt();` action is the reaction to such situation.
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