public <K> void deleteTimer(K key) {
    final ScheduledFuture<?> scheduledFuture = scheduledFutures.remove(key);
    if (scheduledFuture != null) {
      scheduledFuture.cancel(false);
    }
  }
For run loop to listen to timer firing so it can schedule the callbacks.
samza-core/src/main/java/org/apache/samza/scheduler/EpochTimeScheduler.java