dajac commented on code in PR #13961:
URL: https://github.com/apache/kafka/pull/13961#discussion_r1255503145
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group-coordinator/src/main/java/org/apache/kafka/coordinator/group/runtime/CoordinatorRuntime.java:
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@@ -190,6 +216,127 @@ boolean canTransitionFrom(CoordinatorState state) {
abstract boolean canTransitionFrom(CoordinatorState state);
}
+ /**
+ * The EventBasedCoordinatorTimer implements the CoordinatorTimer
interface and provides an event based
+ * timer which turns timeouts of a regular {@link Timer} into {@link
CoordinatorWriteEvent} events which
+ * are executed by the {@link CoordinatorEventProcessor} used by this
coordinator runtime. This is done
+ * to ensure that the timer respects the threading model of the
coordinator runtime.
+ *
+ * The {@link CoordinatorWriteEvent} events pushed by the coordinator
timer wraps the
+ * {@link TimeoutOperation} operations scheduled by the coordinators.
+ *
+ * It also keeps track of all the scheduled {@link TimerTask}. This allows
timeout operations to be
+ * cancelled or rescheduled. When a timer is cancelled or overridden, the
previous timer is guaranteed to
+ * not be executed even if it already expired and got pushed to the event
processor.
+ *
+ * When a timer fails with an unexpected exception, the timer is
rescheduled with a backoff.
+ */
+ class EventBasedCoordinatorTimer implements CoordinatorTimer<U> {
+ /**
+ * The logger.
+ */
+ final Logger log;
+
+ /**
+ * The topic partition.
+ */
+ final TopicPartition tp;
+
+ /**
+ * The scheduled timers keyed by their key.
+ */
+ final Map<String, TimerTask> tasks = new HashMap<>();
+
+ EventBasedCoordinatorTimer(TopicPartition tp, LogContext logContext) {
+ this.tp = tp;
+ this.log = logContext.logger(EventBasedCoordinatorTimer.class);
+ }
Review Comment:
If you look carefully at the `schedule` method, there is the following:
```
log.debug("Registering timer {} with delay of {}ms.", key,
unit.toMillis(delay));
TimerTask prevTask = tasks.put(key, task);
if (prevTask != null) prevTask.cancel();
timer.add(task);
```
So the task is added to the Timer object.
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