(defn setup-ticks! [worker executor-data]
  (let [storm-conf (:storm-conf executor-data)
        tick-time-secs (storm-conf TOPOLOGY-TICK-TUPLE-FREQ-SECS)
        receive-queue (:receive-queue executor-data)
        context (:worker-context executor-data)]
    (when tick-time-secs
      (if (or (system-id? (:component-id executor-data))
              (and (= false (storm-conf TOPOLOGY-ENABLE-MESSAGE-TIMEOUTS))
                   (= :spout (:type executor-data))))
        (log-message "Timeouts disabled for executor " (:component-id executor-data) ":" (:executor-id executor-data))
        (schedule-recurring
          (:user-timer worker)
          tick-time-secs
          tick-time-secs
          (fn []
            (disruptor/publish
              receive-queue
              [[nil (TupleImpl. context [tick-time-secs] Constants/SYSTEM_TASK_ID Constants/SYSTEM_TICK_STREAM_ID)]]
              )))))))

public static boolean isTick(Tuple tuple) {
    return tuple != null
           && Constants.SYSTEM_COMPONENT_ID  .equals(tuple.getSourceComponent())
           && Constants.SYSTEM_TICK_STREAM_ID.equals(tuple.getSourceStreamId());
}

;; 请注意SYSTEM_TASK_ID和SYSTEM_TICK_STREAM_ID
(TupleImpl. context [tick-time-secs] Constants/SYSTEM_TASK_ID Constants/SYSTEM_TICK_STREAM_ID)

    public String getComponentId(int taskId) {
        if(taskId==Constants.SYSTEM_TASK_ID) {
            return Constants.SYSTEM_COMPONENT_ID;
        } else {
            return _taskToComponent.get(taskId);
        }
    }

    String spoutId = "wordGenerator";
    String counterId = "counter";
    String intermediateRankerId = "intermediateRanker";
    String totalRankerId = "finalRanker";
    // 这里，假设TestWordSpout就是我们发送话题tuple的源
    builder.setSpout(spoutId, new TestWordSpout(), 5);
    // RollingCountBolt的时间窗口为9秒钟，每3秒发送一次统计结果到下游
    builder.setBolt(counterId, new RollingCountBolt(9, 3), 4).fieldsGrouping(spoutId, new Fields("word"));
    // IntermediateRankingsBolt，将完成部分聚合，统计出top-n的话题
    builder.setBolt(intermediateRankerId, new IntermediateRankingsBolt(TOP_N), 4).fieldsGrouping(counterId, new Fields(
        "obj"));
        // TotalRankingsBolt， 将完成完整聚合，统计出top-n的话题
    builder.setBolt(totalRankerId, new TotalRankingsBolt(TOP_N)).globalGrouping(intermediateRankerId);

  @Override
  public void execute(Tuple tuple) {
    if (TupleUtils.isTick(tuple)) {
      LOG.debug("Received tick tuple, triggering emit of current window counts");
      // tick来了，将时间窗口内的统计结果发送，并让窗口滚动
      emitCurrentWindowCounts();
    }
    else {
      // 常规tuple，对话题计数即可
      countObjAndAck(tuple);
    }
  }

  // obj即为话题，增加一个计数 count++
  // 注意，这里的速度基本取决于流的速度，可能每秒百万，也可能每秒几十.
  // 内存不足？ bolt可以scale-out.
  private void countObjAndAck(Tuple tuple) {
    Object obj = tuple.getValue(0);
    counter.incrementCount(obj);
    collector.ack(tuple);
  }

  // 将统计结果发送到下游
  private void emitCurrentWindowCounts() {
    Map<Object, Long> counts = counter.getCountsThenAdvanceWindow();
    int actualWindowLengthInSeconds = lastModifiedTracker.secondsSinceOldestModification();
    lastModifiedTracker.markAsModified();
    if (actualWindowLengthInSeconds != windowLengthInSeconds) {
      LOG.warn(String.format(WINDOW_LENGTH_WARNING_TEMPLATE, actualWindowLengthInSeconds, windowLengthInSeconds));
    }
    emit(counts, actualWindowLengthInSeconds);
  }

  public final void execute(Tuple tuple, BasicOutputCollector collector) {
    if (TupleUtils.isTick(tuple)) {
      getLogger().debug("Received tick tuple, triggering emit of current rankings");
      // 将聚合并排序的结果发送到下游
      emitRankings(collector);
    }
    else {
      // 聚合并排序
      updateRankingsWithTuple(tuple);
    }
  }

// IntermediateRankingsBolt的聚合排序方法：
  @Override
  void updateRankingsWithTuple(Tuple tuple) {
    // 这一步，将话题、话题出现的次数提取出来
    Rankable rankable = RankableObjectWithFields.from(tuple);
    // 这一步，将话题出现的次数进行聚合，然后重排序所有话题
    super.getRankings().updateWith(rankable);
  }

// TotalRankingsBolt的聚合排序方法
  @Override
  void updateRankingsWithTuple(Tuple tuple) {
  // 提出来自IntermediateRankingsBolt的中间结果
    Rankings rankingsToBeMerged = (Rankings) tuple.getValue(0);
  // 聚合并排序
    super.getRankings().updateWith(rankingsToBeMerged);
  // 去0，节约内存
    super.getRankings().pruneZeroCounts();
  }

  private void rerank() {
    Collections.sort(rankedItems);
    Collections.reverse(rankedItems);
  }