12_Flink Streaming cluster

在此之前的都是如何编写api，制作topology的过程。提交到集群后，就是运行topology了。运行时的模块大多都是scala写的，可能是因为使用akka通信。之前绘制DAG的过程大多是java写的。

flink的cluster有两种，LocalFlinkMiniCluster和FlinkMiniCluster，本地运行时是LocalFlinkMiniCluster，集群运行时是FlinkMiniCluster。LocalFlinkMiniCluster是在jvm中使用多线程模拟分布式计算。研究这个意义较小。所以研究一下FlinkMiniCluster。

FlinkMiniCluster。

在了解集群之前。先了解flink的架构。flink runtime 集群由1个JobManager（非HA）和多个TaskManager。组成。

JobManager，负责接收Client请求，统一管理TaskManager。类似storm的nimbus和worker的关系。

TaskManager，管理Task任务的执行。

以下简称JM和TM

JM和TM的通信由akka实现。两者都实现了FlinkActor。通过handleMessage方法，传递不同的Message进行通信。

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime

import _root_.akka.actor.Actor
import grizzled.slf4j.Logger

/** Base trait for Flink's actors.
  *
  * The message handling logic is defined in the handleMessage method. This allows to mixin
  * stackable traits which change the message receiving behaviour.
  */
trait FlinkActor extends Actor {
  val log: Logger

  override def receive: Receive = handleMessage

  /** Handle incoming messages
    *
    * @return
    */
  def handleMessage: Receive

  /** Factory method for messages. This method can be used by mixins to decorate messages
    *
    * @param message The message to decorate
    * @return The decorated message
    */
  def decorateMessage(message: Any): Any = {
    message
  }
}

TaskManager

/**
   * Central handling of actor messages. This method delegates to the more specialized
   * methods for handling certain classes of messages.
   */
  override def handleMessage: Receive = {
    // task messages are most common and critical, we handle them first
    case message: TaskMessage => handleTaskMessage(message)

    // messages for coordinating checkpoints
    case message: AbstractCheckpointMessage => handleCheckpointingMessage(message)

    case JobManagerLeaderAddress(address, newLeaderSessionID) =>
      handleJobManagerLeaderAddress(address, newLeaderSessionID)

    // registration messages for connecting and disconnecting from / to the JobManager
    case message: RegistrationMessage => handleRegistrationMessage(message)

    // task sampling messages
    case message: StackTraceSampleMessages => handleStackTraceSampleMessage(message)

    // ----- miscellaneous messages ----

    // periodic heart beats that transport metrics
    case SendHeartbeat => sendHeartbeatToJobManager()

    // sends the stack trace of this TaskManager to the sender
    case SendStackTrace => sendStackTrace(sender())

    // registers the message sender to be notified once this TaskManager has completed
    // its registration at the JobManager
    case NotifyWhenRegisteredAtJobManager =>
      if (isConnected) {
        sender ! decorateMessage(RegisteredAtJobManager)
      } else {
        waitForRegistration += sender
      }

    // this message indicates that some actor watched by this TaskManager has died
    case Terminated(actor: ActorRef) =>
      if (isConnected && actor == currentJobManager.orNull) {
          handleJobManagerDisconnect(sender(), "JobManager is no longer reachable")
          triggerTaskManagerRegistration()
      } else {
        log.warn(s"Received unrecognized disconnect message " +
            s"from ${if (actor == null) null else actor.path}.")
      }

    case Disconnect(msg) =>
      handleJobManagerDisconnect(sender(), s"JobManager requested disconnect: $msg")
      triggerTaskManagerRegistration()

    case msg: StopCluster =>
      log.info(s"Stopping TaskManager with final application status ${msg.finalStatus()} " +
        s"and diagnostics: ${msg.message()}")
      shutdown()

    case FatalError(message, cause) =>
      killTaskManagerFatal(message, cause)

    case RequestTaskManagerLog(requestType : LogTypeRequest) =>
      blobService match {
        case Some(_) =>
          handleRequestTaskManagerLog(sender(), requestType, currentJobManager.get)
        case None =>
          sender() ! new IOException("BlobService not available. Cannot upload TaskManager logs.")
      }
  }

  /**
   * Handle unmatched messages with an exception.
   */
  override def unhandled(message: Any): Unit = {
    val errorMessage = "Received unknown message " + message
    val error = new RuntimeException(errorMessage)
    log.error(errorMessage)

    // terminate all we are currently running (with a dedicated message)
    // before the actor is stopped
    cancelAndClearEverything(error)

    // let the actor crash
    throw error
  }

JobManager

/**
   * Central work method of the JobManager actor. Receives messages and reacts to them.
   *
   * @return
   */
  override def handleMessage: Receive = {

    case GrantLeadership(newLeaderSessionID) =>
      log.info(s"JobManager $getAddress was granted leadership with leader session ID " +
        s"$newLeaderSessionID.")

      leaderSessionID = newLeaderSessionID

      // confirming the leader session ID might be blocking, thus do it in a future
      future {
        leaderElectionService.confirmLeaderSessionID(newLeaderSessionID.orNull)

        // TODO (critical next step) This needs to be more flexible and robust (e.g. wait for task
        // managers etc.)
        if (recoveryMode != RecoveryMode.STANDALONE) {
          log.info(s"Delaying recovery of all jobs by $jobRecoveryTimeout.")

          context.system.scheduler.scheduleOnce(
            jobRecoveryTimeout,