(defserverfn mk-supervisor [conf shared-context ^ISupervisor isupervisor]
  (log-message "Starting Supervisor with conf " conf)
  (.prepare isupervisor conf (supervisor-isupervisor-dir conf)) ;;初始化supervisor-id,并存在localstate中(参考ISupervisor的实现)

(FileUtils/cleanDirectory (File. (supervisor-tmp-dir conf))) ;;清空本机的supervisor目录
  (let [supervisor (supervisor-data conf shared-context isupervisor)
;;创建两个event-manager,用于在后台执行function
        [event-manager processes-event-manager :as managers] [(event/event-manager false) (event/event-manager false)]                         
        sync-processes (partial sync-processes supervisor) ;;partial sync-process
        ;;mk-synchronize-supervisor, mk-supervisor的主要工作,参考下面
        synchronize-supervisor (mk-synchronize-supervisor supervisor sync-processes event-manager processes-event-manager)
        ;;定义生成supervisor hb的funciton
        heartbeat-fn (fn [] (.supervisor-heartbeat!
                               (:storm-cluster-state supervisor)
                               (:supervisor-id supervisor)
                               (SupervisorInfo. (current-time-secs)
                                                (:my-hostname supervisor)
                                                (:assignment-id supervisor)
                                                (keys @(:curr-assignment supervisor))
                                                ;; used ports
                                                (.getMetadata isupervisor)
                                                (conf SUPERVISOR-SCHEDULER-META)
                                                ((:uptime supervisor)))))]
    ;;先调用heartbeat-fn发送一次supervisor的hb

    ;;接着使用schedule-recurring去定期调用heartbeat-fn更新hb

    (heartbeat-fn)
    ;; should synchronize supervisor so it doesn't launch anything after being down (optimization)
    (schedule-recurring (:timer supervisor)
                        0
                        (conf SUPERVISOR-HEARTBEAT-FREQUENCY-SECS)
                        heartbeat-fn))

(defn mk-synchronize-supervisor [supervisor sync-processes event-manager processes-event-manager]
  (fn this []
    (let [conf (:conf supervisor)
          storm-cluster-state (:storm-cluster-state supervisor)
          ^ISupervisor isupervisor (:isupervisor supervisor)
          ^LocalState local-state (:local-state supervisor) ;;本地缓存数据库
          sync-callback (fn [& ignored] (.add event-manager this)) ;;生成callback函数(后台执行mk-synchronize-supervisor)
          assignments-snapshot (assignments-snapshot storm-cluster-state sync-callback) ;;读取assignments,并注册callback,在zk->assignment发生变化时被触发
          storm-code-map (read-storm-code-locations assignments-snapshot) ;;从哪儿下载topology code
          downloaded-storm-ids (set (read-downloaded-storm-ids conf)) ;;已经下载了哪些topology
          all-assignment (read-assignments  ;;supervisor的port上被分配了哪些executors
                           assignments-snapshot
                           (:assignment-id supervisor)) ;;supervisor-id
          new-assignment (->> all-assignment ;;new=all,因为confirmAssigned没有具体实现,always返回true
                              (filter-key #(.confirmAssigned isupervisor %)))
          assigned-storm-ids (assigned-storm-ids-from-port-assignments new-assignment) ;;supervisor上被分配的topology id集合
           existing-assignment (.get local-state LS-LOCAL-ASSIGNMENTS)] ;;从local-state数据库里面读出当前保存的local assignments
      
      ;;下载新分配的topology代码
      (doseq [[storm-id master-code-dir] storm-code-map]
        (when (and (not (downloaded-storm-ids storm-id))
                   (assigned-storm-ids storm-id))
         (download-storm-code conf storm-id master-code-dir)))     

      (.put local-state     ;;把new-assignment存到local-state数据库中
            LS-LOCAL-ASSIGNMENTS
            new-assignment)
      (reset! (:curr-assignment supervisor) new-assignment) ;;把new-assignment cache到supervisor对象中
       

      ;;删除无用的topology code 
      ;;remove any downloaded code that's no longer assigned or active
      (doseq [storm-id downloaded-storm-ids]
        (when-not (assigned-storm-ids storm-id)
          (log-message "Removing code for storm id " storm-id)
          (rmr (supervisor-stormdist-root conf storm-id))
          ))

      ;;后台执行sync-processes
      (.add processes-event-manager sync-processes)
      )))

(defn sync-processes [supervisor]
  (let [conf (:conf supervisor)
        ^LocalState local-state (:local-state supervisor)
        assigned-executors (defaulted (.get local-state LS-LOCAL-ASSIGNMENTS) {})
        now (current-time-secs)
        allocated (read-allocated-workers supervisor assigned-executors now) ;;1.读取当前worker的状况
        keepers (filter-val     ;;找出状态为valid的worker
                 (fn [[state _]] (= state :valid))
                 allocated)
        keep-ports (set (for [[id [_ hb]] keepers] (:port hb))) ;;keepers的ports集合

         ;;select-keys-pred(pred map), 对map中的key使用pred进行过滤

         ;;找出assigned-executors中executor的port, 哪些不属于keep-ports, 

        ;;即找出新被assign的workers或那些虽被assign但状态不是valid的workers(dead或没有start)
        ;;这些executors需要从新分配到新的worker上去
        reassign-executors (select-keys-pred (complement keep-ports) assigned-executors)
        new-worker-ids (into  
                        {}
                        (for [port (keys reassign-executors)]  ;;为reassign-executors的port产生新的worker-id
                          [port (uuid)]))
        ]
    ;; 1. to kill are those in allocated that are dead or disallowed
    ;; 2. kill the ones that should be dead
    ;;     - read pids, kill -9 and individually remove file
    ;;     - rmr heartbeat dir, rmdir pid dir, rmdir id dir (catch exception and log)
    ;; 3. of the rest, figure out what assignments aren't yet satisfied
    ;; 4. generate new worker ids, write new "approved workers" to LS
    ;; 5. create local dir for worker id
    ;; 5. launch new workers (give worker-id, port, and supervisor-id)
    ;; 6. wait for workers launch  
    (doseq [[id [state heartbeat]] allocated]
      (when (not= :valid state)  ;;shutdown所有状态不是valid的worker
       (shutdown-worker supervisor id)))
    (doseq [id (vals new-worker-ids)]
      (local-mkdirs (worker-pids-root conf id))) ;;为新的worker创建目录, 并加到local-state的LS-APPROVED-WORKERS中
    (.put local-state LS-APPROVED-WORKERS   ;;更新的approved worker, 状态为valid的 + new workers
          (merge
           (select-keys (.get local-state LS-APPROVED-WORKERS) ;;现有approved worker中状态为valid
                        (keys keepers))
           (zipmap (vals new-worker-ids) (keys new-worker-ids)) ;;new workers 
           ))
    (wait-for-workers-launch ;;2.wait-for-workers-launch 
     conf
     (dofor [[port assignment] reassign-executors]
       (let [id (new-worker-ids port)]
         (launch-worker supervisor
                        (:storm-id assignment)
                        port
                        id)
         id)))
    ))

(defn read-allocated-workers
  "Returns map from worker id to worker heartbeat. if the heartbeat is nil, then the worker is dead (timed out or never wrote heartbeat)"
  [supervisor assigned-executors now]
  (let [conf (:conf supervisor)
        ^LocalState local-state (:local-state supervisor)
;从local-state中读出每个worker的hb, 当然每个worker进程会不断的更新本地hb    
        id->heartbeat (read-worker-heartbeats conf) 

        approved-ids (set (keys (.get local-state LS-APPROVED-WORKERS)))] ;;从local-state读出approved的worker
    (into
     {}
     (dofor [[id hb] id->heartbeat] ;;根据hb来判断worker的当前状态
            (let [state (cond
                         (or (not (contains? approved-ids id))
                             (not (matches-an-assignment? hb assigned-executors)))
                           :disallowed  ;;不被允许
                         (not hb)
                           :not-started ;;无hb,没有start
                         (> (- now (:time-secs hb))
                            (conf SUPERVISOR-WORKER-TIMEOUT-SECS))
                           :timed-out  ;;超时,dead
                         true
                           :valid)]
              (log-debug "Worker " id " is " state ": " (pr-str hb) " at supervisor time-secs " now)
              [id [state hb]] ;;返回每个worker的当前state和hb
              ))
     )))

(defn- wait-for-worker-launch [conf id start-time]
  (let [state (worker-state conf id)]    
    (loop []
      (let [hb (.get state LS-WORKER-HEARTBEAT)]
        (when (and
               (not hb)
               (<
                (- (current-time-secs) start-time)
                (conf SUPERVISOR-WORKER-START-TIMEOUT-SECS)
                ))
          (log-message id " still hasn't started")
          (Time/sleep 500)
          (recur)
          )))
    (when-not (.get state LS-WORKER-HEARTBEAT)
      (log-message "Worker " id " failed to start")
      )))

(defn- wait-for-workers-launch [conf ids]
  (let [start-time (current-time-secs)]
    (doseq [id ids]
      (wait-for-worker-launch conf id start-time))
    ))

本文章摘自博客园，原文发布日期：2013-06-28