code: public void taskletComplete(final int taskletId, final Object result) {
      final boolean aggregateOnCount;
      synchronized (stateLock) {
        completedTasklets.add(new ImmutablePair<>(taskletId, result));
        removePendingTaskletReferenceCount(taskletId);
        aggregateOnCount = aggregateOnCount();
      }
  
      if (aggregateOnCount) {
        aggregateTasklets(AggregateTriggerType.COUNT);
      }
    }
docs: Reported when an associated tasklet is complete and adds it to the completion pool.