大数据IMF传奇行动绝密课程第30课：Master的注册机制和状态管理解密

Master的注册机制和状态管理解密

一、Master接受Driver注册内幕
二、Master接受Application注册内幕
三、Master接受Worker注册内幕
四、Master处理Driver状态变化内幕
五、Master处理Executor状态变化内幕

一、Master对其它组建注册的处理
1、Master接受注册的对象主要是:Driver、Application、Worker；需要补充说明的是Executor不会注册个Master，Executor是注册给Driver中的SchedulerBackend的；
2、Worker是在启动后主动向Master注册的，所以如果在生产环境下加入新的Worker到已经正在运行的Spark集群上，此时不需要重新启动Spark集群就能够使用新加入的Worker以提升处理能力；

//Master.scala中部分代码  override def receiveAndReply(context: RpcCallContext): PartialFunction[Any, Unit] = {    case RegisterWorker(        id, workerHost, workerPort, workerRef, cores, memory, workerUiPort, publicAddress) => {      logInfo("Registering worker %s:%d with %d cores, %s RAM".format(        workerHost, workerPort, cores, Utils.megabytesToString(memory)))      if (state == RecoveryState.STANDBY) {        context.reply(MasterInStandby)      } else if (idToWorker.contains(id)) {        context.reply(RegisterWorkerFailed("Duplicate worker ID"))      } else {        val worker = new WorkerInfo(id, workerHost, workerPort, cores, memory,          workerRef, workerUiPort, publicAddress)        if (registerWorker(worker)) {          persistenceEngine.addWorker(worker)          context.reply(RegisteredWorker(self, masterWebUiUrl))          schedule()        } else {          val workerAddress = worker.endpoint.address          logWarning("Worker registration failed. Attempted to re-register worker at same " +            "address: " + workerAddress)          context.reply(RegisterWorkerFailed("Attempted to re-register worker at same address: "            + workerAddress))        }      }    }

3、Master在接收到Worker注册的请求后，首先会判断一下当前的Master是否是Standby的模式，如果是的话就不处理；然后会判断当前Master的内存数据结构idToWorker中是否已经有该Worker的注册信息，如果有的话此时不会重复注册；
4、Master如果决定接收注册的Worker，首先会创建WorkerInfo对象来保存注册的Worker的信息；
private[spark] class WorkerInfo(
val id: String,
val host: String,
val port: Int,
val cores: Int,
val memory: Int,
val endpoint: RpcEndpointRef,
val webUiPort: Int,
val publicAddress: String)
然后调用registerWorker来执行具体的注册的过程，如果Worker的状态是DEAD，则直接过滤掉，对于UNKNOWN状态的内容调用removeWorker进行清理（包括清理该Worker下的Executors和Drivers）

5、注册时是先注册Driver，然后再注册Application

二、Master对Driver和Executor状态变化的处理
1、对Driver状态变化的处理

//Master.scala中部分代码case DriverState.ERROR | DriverState.FINISHED | DriverState.KILLED | DriverState.FAILED =>  removeDriver(driverId, state, exception)private def removeDriver(  driverId: String,  finalState: DriverState,  exception: Option[Exception]) {drivers.find(d => d.id == driverId) match {  case Some(driver) =>    logInfo(s"Removing driver: $driverId")    drivers -= driver    if (completedDrivers.size >= RETAINED_DRIVERS) {      val toRemove = math.max(RETAINED_DRIVERS / 10, 1)      completedDrivers.trimStart(toRemove)    }    completedDrivers += driver    persistenceEngine.removeDriver(driver)    driver.state = finalState    driver.exception = exception    driver.worker.foreach(w => w.removeDriver(driver))    schedule()  case None =>    logWarning(s"Asked to remove unknown driver: $driverId")}}

2、Executor挂掉的时候系统会尝试一定次数的重启（最多重试10次重启）

//Master.scala中部分代码case ExecutorStateChanged(appId, execId, state, message, exitStatus) => {  val execOption = idToApp.get(appId).flatMap(app => app.executors.get(execId))  execOption match {    case Some(exec) => {      val appInfo = idToApp(appId)      val oldState = exec.state      exec.state = state      if (state == ExecutorState.RUNNING) {        assert(oldState == ExecutorState.LAUNCHING,          s"executor $execId state transfer from $oldState to RUNNING is illegal")        appInfo.resetRetryCount()      }      exec.application.driver.send(ExecutorUpdated(execId, state, message, exitStatus))      if (ExecutorState.isFinished(state)) {        // Remove this executor from the worker and app        logInfo(s"Removing executor ${exec.fullId} because it is $state")        // If an application has already finished, preserve its        // state to display its information properly on the UI        if (!appInfo.isFinished) {          appInfo.removeExecutor(exec)        }        exec.worker.removeExecutor(exec)        val normalExit = exitStatus == Some(0)        // Only retry certain number of times so we don't go into an infinite loop.        if (!normalExit) {          if (appInfo.incrementRetryCount() < ApplicationState.MAX_NUM_RETRY) {            schedule()          } else {            val execs = appInfo.executors.values            if (!execs.exists(_.state == ExecutorState.RUNNING)) {              logError(s"Application ${appInfo.desc.name} with ID ${appInfo.id} failed " +                s"${appInfo.retryCount} times; removing it")              removeApplication(appInfo, ApplicationState.FAILED)            }          }        }      }    }    case None =>      logWarning(s"Got status update for unknown executor $appId/$execId")  }}