spark的master和worker起不来 spark master slave

Master主备切换

Master的主备切换分为两种：基于文件系统和基于zookeeper

• 基于文件系统的，spark提供目录保存spark Application和worker的注册信息，并将他们的恢复状态写入该目录，当spark的master节点宕掉的时候，重启master，就能获取application和worker的注册信息。需要手动进行切换
• 基于zookeeper的，用于生产模式。其基本原理是通过zookeeper来选举一个Master，其他的Master处于Standby状态。将Standalone集群连接到同一个ZooKeeper实例并启动多个Master，利用zookeeper提供的选举和状态保存功能，可以使一个Master被选举，而其他Master处于Standby状态。如果现任Master死去，另一个Master会通过选举产生，并恢复到旧的Master状态，然后恢复调度。

因为涉及到多个Master，需要在SparkContext指向一个Master列表，spark://host1:port1,host2:port2,host3:port3，应用程序会轮询列表

不能将Master定义在conf/spark-env.sh里了，而是直接在Application中定义。涉及的参数是 export SPARK_MASTER_IP=bigdata001，这项不配置或者为空。否则，无法启动多个master

流程：（注意completeRecovery方法）

• 在active Master宕掉之后，内部持久化(FileSystemPersistenceEngine和ZookeeperPersistenceEngine)引擎首先会读取持久化的storedApps、storedDrivers、storedWorkers
• 如果storedApps、storedWorkers有任何一个是有内容的，那么就将持久化的Application、Worker信息重新注册
• 将Application和Worker的状态都修改为UNKNOWN，然后向Application所对应的Driver和Worker发送StandBy Master的地址
• 如果Driver和Wroker是正常运转的情况下，接收到Master发送过来的地址后，就会相应到新的Master，在Master陆续接收到Driver和Worker发送过来的消息后，会使用completeRecovery()方法对没有发送响应消息的Driver和Worker进行处理，过滤掉他们的信息。
• 调用Master的schedule()方法，对正在调度的Driver和Application进行调度。在worker上启动driver，或者是为Applicaiton在worker上启动executor

看看beginRecover代码：

private def canCompleteRecovery =
    workers.count(_.state == WorkerState.UNKNOWN) == 0 &&
      apps.count(_.state == ApplicationState.UNKNOWN) == 0

  private def beginRecovery(storedApps: Seq[ApplicationInfo], storedDrivers: Seq[DriverInfo],
      storedWorkers: Seq[WorkerInfo]) {
    for (app <- storedApps) {
      logInfo("Trying to recover app: " + app.id)
      try {
        registerApplication(app)
        app.state = ApplicationState.UNKNOWN
        app.driver.send(MasterChanged(self, masterWebUiUrl))
      } catch {
        case e: Exception => logInfo("App " + app.id + " had exception on reconnect")
      }
    }

    for (driver <- storedDrivers) {
      // Here we just read in the list of drivers. Any drivers associated with now-lost workers
      // will be re-launched when we detect that the worker is missing.
      drivers += driver
    }

    for (worker <- storedWorkers) {
      logInfo("Trying to recover worker: " + worker.id)
      try {
        registerWorker(worker)
        worker.state = WorkerState.UNKNOWN
        worker.endpoint.send(MasterChanged(self, masterWebUiUrl))
      } catch {
        case e: Exception => logInfo("Worker " + worker.id + " had exception on reconnect")
      }
    }
  }

可以看到，形参三个，storedApps、storedDrivers、storedWorkers
对于storedApps：

for (app <- storedApps) {
      logInfo("Trying to recover app: " + app.id)
      try {
        registerApplication(app) //直接注册
        app.state = ApplicationState.UNKNOWN //设置状态为UNKONWN
        app.driver.send(MasterChanged(self, masterWebUiUrl))//发送备用master信息
      } catch {
        case e: Exception => logInfo("App " + app.id + " had exception on reconnect")
      }
    }

对于storedDrivers：

for (driver <- storedDrivers) {
      // Here we just read in the list of drivers. Any drivers associated with now-lost workers
      // will be re-launched when we detect that the worker is missing.
	
      drivers += driver
    }

在这里，我们只是阅读了Drivers程序列表。当我们检测到Workers失踪时，任何与现在失踪工人相关的Workers程序都将重新启动。

对于storedWorkers：

for (worker <- storedWorkers) {
      logInfo("Trying to recover worker: " + worker.id)
      try {
        registerWorker(worker)
        worker.state = WorkerState.UNKNOWN
        worker.endpoint.send(MasterChanged(self, masterWebUiUrl))
      } catch {
        case e: Exception => logInfo("Worker " + worker.id + " had exception on reconnect")
      }
    }

---

再看看completeRecovery代码

private def completeRecovery() {
    // Ensure "only-once" recovery semantics using a short synchronization period.
    if (state != RecoveryState.RECOVERING) { return }
    state = RecoveryState.COMPLETING_RECOVERY

    // Kill off any workers and apps that didn't respond to us.
    workers.filter(_.state == WorkerState.UNKNOWN).foreach(removeWorker)
    apps.filter(_.state == ApplicationState.UNKNOWN).foreach(finishApplication)

    // Reschedule drivers which were not claimed by any workers
    drivers.filter(_.worker.isEmpty).foreach { d =>
      logWarning(s"Driver ${d.id} was not found after master recovery")
      if (d.desc.supervise) {
        logWarning(s"Re-launching ${d.id}")
        relaunchDriver(d)
      } else {
        removeDriver(d.id, DriverState.ERROR, None)
        logWarning(s"Did not re-launch ${d.id} because it was not supervised")
      }
    }
	state = RecoveryState.ALIVE
   	 	schedule()
    	logInfo("Recovery complete - resuming operations!")
  }

可以看到，进来就进行Driver和Worker的过滤

// Kill off any workers and apps that didn't respond to us.
 //杀死所有没有回应我们的Workers和Apps。
    workers.filter(_.state == WorkerState.UNKNOWN).foreach(removeWorker)
    apps.filter(_.state == ApplicationState.UNKNOWN).foreach(finishApplication)

进来removeWorker看看

private def removeWorker(worker: WorkerInfo) {
    logInfo("Removing worker " + worker.id + " on " + worker.host + ":" + worker.port)
    worker.setState(WorkerState.DEAD) //设置状态为DEAD
    idToWorker -= worker.id //从内存结构中移除
    addressToWorker -= worker.endpoint.address
    if (reverseProxy) {
      webUi.removeProxyTargets(worker.id)
    }
    for (exec <- worker.executors.values) {
      logInfo("Telling app of lost executor: " + exec.id)
      exec.application.driver.send(ExecutorUpdated(
        exec.id, ExecutorState.LOST, Some("worker lost"), None, workerLost = true))
      exec.state = ExecutorState.LOST
      exec.application.removeExecutor(exec) //移除driver上的executors
    }
    for (driver <- worker.drivers.values) {
      if (driver.desc.supervise) { //driver属性
        logInfo(s"Re-launching ${driver.id}")
        relaunchDriver(driver) //对于Driver，driver.desc.supervise为true就先尝试重启
      } else {
        logInfo(s"Not re-launching ${driver.id} because it was not supervised")
        removeDriver(driver.id, DriverState.ERROR, None)
      }
    }
    persistenceEngine.removeWorker(worker)
  }

完了最后会调用schedule()方法，后面再看。