Master.preStart(){　　webUi.bind()　　context.system.scheduler.schedule(0 millis, WORKER_TIMEOUT millis, self, CheckForWorkerTimeOut) //定时任务检测是否有DEAD WORKER需要移除　　case CheckForWorkerTimeOut => {　　　　timeOutDeadWorkers()　　}　　/** Check for, and remove, any timed-out workers */　　　　def timeOutDeadWorkers() {　　　　...　　　　if (worker.lastHeartbeat < currentTime - ((REAPER_ITERATIONS + 1) * WORKER_TIMEOUT)) {　　　　　　workers -= worker 　　　　}　　}}

Worker.preStart(){　　override def preStart() {　　　　webUi = new WorkerWebUI(this, workDir, Some(webUiPort))　　　　webUi.bind()　　　　registerWithMaster()  //注册该Worker到Master　　}　　def tryRegisterAllMasters() {　　　　for (masterUrl <- masterUrls) {　　　　　　logInfo("Connecting to master " + masterUrl + "...")　　　　　　val actor = context.actorSelection(Master.toAkkaUrl(masterUrl))　　　　　　actor ! RegisterWorker(workerId, host, port, cores, memory, webUi.boundPort, publicAddress)　　　　}　　}}

Master.scalacase RegisterWorker(){　　　　persistenceEngine.addWorker(worker)　　sender ! RegisteredWorker(masterUrl, masterWebUiUrl)  //向Worker发送Worker注册成功事件　　schedule()  //调度部分后续章节分析  }

Worker.scalacase RegisteredWorker(){　　registered = true　　context.system.scheduler.schedule(0 millis, HEARTBEAT_MILLIS millis, self, SendHeartbeat)  //Worker注册成功后，定时向Master发送心跳信息}case SendHeartbeat =>　　masterLock.synchronized {　　if (connected) { master ! Heartbeat(workerId) }}

Master.scalacase Heartbeat(workerId) => {　　idToWorker.get(workerId) match {　　case Some(workerInfo) =>　　　　workerInfo.lastHeartbeat = System.currentTimeMillis()  //更新该worker的上次发送心跳信息的时间　　case None =>　　　　logWarning("Got heartbeat from unregistered worker " + workerId)　　}}

SparkContext.createTaskScheduler()　　==>new SparkDeploySchedulerBackend()　　　　==>创建AppClient并启动　　　　　　==>ClientActor.preStart():registerWithMaster(){actor ! RegisterApplication(appDescription)}  //向Master发起RegisterApplication事件

Master.scalacase RegisterApplication(description) {　　val app = createApplication(description, sender)　　registerApplication(app)　　persistenceEngine.addApplication(app)　　sender ! RegisteredApplication(app.id, masterUrl)  //向Worker发起RegisteredApplication事件表示该Application已经注册成功　　schedule()}