(defn mk-executor [worker executor-id]
  (let [executor-data (mk-executor-data worker executor-id) ;;1.mk-executor-data 
        _ (log-message "Loading executor " (:component-id executor-data) ":" (pr-str executor-id))
        task-datas (->> executor-data
                        :task-ids
                        (map (fn [t] [t (task/mk-task executor-data t)])) ;;2.mk-task 
                        (into {})
                        (HashMap.))
        _ (log-message "Loaded executor tasks " (:component-id executor-data) ":" (pr-str executor-id))
        report-error-and-die (:report-error-and-die executor-data)
        component-id (:component-id executor-data)

        ;;3.创建threads 

        ;; starting the batch-transfer->worker ensures that anything publishing to that queue 
        ;; doesn't block (because it's a single threaded queue and the caching/consumer started
        ;; trick isn't thread-safe)
        system-threads [(start-batch-transfer->worker-handler! worker executor-data)]
        handlers (with-error-reaction report-error-and-die
                   (mk-threads executor-data task-datas))
        threads (concat handlers system-threads)]

    
    ;;使用schedule-recurring定期产生SYSTEM_TICK(触发spout pending rotate) 

    (setup-ticks! worker executor-data) 

(defn mk-executor-data [worker executor-id]
  (let [worker-context (worker-context worker)
        task-ids (executor-id->tasks executor-id) ;;包含的tasks
        component-id (.getComponentId worker-context (first task-ids)) ;;所属于的component
        storm-conf (normalized-component-conf (:storm-conf worker) worker-context component-id)
        executor-type (executor-type worker-context component-id) ;;executor类型, blot或者spout
        batch-transfer->worker (disruptor/disruptor-queue   ;;executor的发送缓存queue
                                  (storm-conf TOPOLOGY-EXECUTOR-SEND-BUFFER-SIZE)
                                  :claim-strategy :single-threaded
                                  :wait-strategy (storm-conf TOPOLOGY-DISRUPTOR-WAIT-STRATEGY))
        ]
    (recursive-map
     :worker worker
     :worker-context worker-context
     :executor-id executor-id
     :task-ids task-ids
     :component-id component-id
     :open-or-prepare-was-called? (atom false)
     :storm-conf storm-conf
     :receive-queue ((:executor-receive-queue-map worker) executor-id) ;;取出executor所对应的disruptor queue
     :storm-id (:storm-id worker)
     :conf (:conf worker)
     :shared-executor-data (HashMap.)
     :storm-active-atom (:storm-active-atom worker)
     :batch-transfer-queue batch-transfer->worker
     :transfer-fn (mk-executor-transfer-fn batch-transfer->worker) ;;(1.1) 
     :suicide-fn (:suicide-fn worker)
     :storm-cluster-state (cluster/mk-storm-cluster-state (:cluster-state worker))
     :type executor-type
     ;; TODO: should refactor this to be part of the executor specific map (spout or bolt with :common field)
     :stats (mk-executor-stats <> (sampling-rate storm-conf)) ;;(1.2)
     :interval->task->metric-registry (HashMap.)
     :task->component (:task->component worker)
     :stream->component->grouper (outbound-components worker-context component-id)
     :report-error (throttled-report-error-fn <>)
     :report-error-and-die (fn [error] ;;将error写到zk的error目录下,其他daemon进程可以知道
                             ((:report-error <>) error)
                             ((:suicide-fn <>)))
     :deserializer (KryoTupleDeserializer. storm-conf worker-context)
     :sampler (mk-stats-sampler storm-conf) ;;1.3 mk-stats-sampler 
     ;; TODO: add in the executor-specific stuff in a :specific... or make a spout-data, bolt-data function?
     )))

        ;; the overflow buffer is used to ensure that spouts never block when emitting
        ;; this ensures that the spout can always clear the incoming buffer (acks and fails), which
        ;; prevents deadlock from occuring across the topology (e.g. Spout -> Bolt -> Acker -> Spout, and all
        ;; buffers filled up)
        ;; when the overflow buffer is full, spouts stop calling nextTuple until it's able to clear the overflow buffer
        ;; this limits the size of the overflow buffer to however many tuples a spout emits in one call of nextTuple, 
        ;; preventing memory issues
        overflow-buffer (LinkedList.)]

;; in its own function so that it can be mocked out by tracked topologies
(defn mk-executor-transfer-fn [batch-transfer->worker]
  (fn this
    ([task tuple block? ^List overflow-buffer]
      (if (and overflow-buffer (not (.isEmpty overflow-buffer))) ;;overflow存在并且不为空,说明queue已经满了,所以直接放overflow-buffer中
        (.add overflow-buffer [task tuple])
        (try-cause
          (disruptor/publish batch-transfer->worker [task tuple] block?)
        (catch InsufficientCapacityException e
          (if overflow-buffer
            (.add overflow-buffer [task tuple])
            (throw e))
          ))))
    ([task tuple overflow-buffer]
      (this task tuple (nil? overflow-buffer) overflow-buffer))
    ([task tuple]
      (this task tuple nil)
      )))

(defn mk-stats-sampler [conf]
  (even-sampler (sampling-rate conf)))

(defn even-sampler [freq]
  (let [freq (int freq)
        start (int 0)
        r (java.util.Random.)
        curr (MutableInt. -1)
        target (MutableInt. (.nextInt r freq))] ;;[0,freq]中的随机值
    (with-meta
      (fn []
        (let [i (.increment curr)]
          (when (>= i freq)
            (.set curr start)
            (.set target (.nextInt r freq))))
          (= (.get curr) (.get target))) ;;FP没有直接赋值, 所以==简化为=
      {:rate freq})))

(defn sampler-rate [sampler]
  (:rate (meta sampler)))

(defn start-batch-transfer->worker-handler! [worker executor-data]
  (let [worker-transfer-fn (:transfer-fn worker)
        cached-emit (MutableObject. (ArrayList.)) ;;用于cache所有messages,直到batchend
        storm-conf (:storm-conf executor-data)
        serializer (KryoTupleSerializer. storm-conf (:worker-context executor-data))
        ]
    (disruptor/consume-loop*
      (:batch-transfer-queue executor-data)
      (disruptor/handler [o seq-id batch-end?]
        (let [^ArrayList alist (.getObject cached-emit)]
          (.add alist o)
          (when batch-end?
            (worker-transfer-fn serializer alist)
            (.setObject cached-emit (ArrayList.))
            )))
      :kill-fn (:report-error-and-die executor-data))))