Flink源码-集群启动之JobManager的启动

主要内容

首先要熟悉flink架构基础知识,了解client、jobmanager、taskmanager的基本用途;本文通过源码角度分析各个组件的启动流程深入理解client、jobmanager、taskmanager的功能和之间的交互
首先集群启动脚本分析,也是便于我们从源头找到阅读flink源码的流程。

集群启动脚本start-cluster

首先集群启动时会执行start-cluster脚本,如下:

$ ./bin/start-cluster.sh

start-cluster核心代码如下:

"${FLINK_BIN_DIR}"/jobmanager.sh start "${master}" "${webuiport}"

如上述会调用jobmanager.sh脚本

     ENTRYPOINT=standalonesession

   "${FLINK_BIN_DIR}"/flink-daemon.sh $STARTSTOP $ENTRYPOINT "${args[@]}"

jommanager.sh脚本中会调用Flink-daemon.sh脚本

    (standalonesession)
        CLASS_TO_RUN=org.apache.flink.runtime.entrypoint.StandaloneSessionClusterEntrypoint 

jobmanager启动的入口类

jobmanager.sh脚本中会调用启动的入口类StandaloneSessionClusterEntrypoint,分析如下:

jobmanager功能概述

概述:jobmanager启动过程首先初始化各种服务(initializeServices(configuration, pluginManager)),包括haServices,blobServer,heartbeatServices,metricRegistry,archivedExecutionGraphStore,之后会启动三大组件WebMonitorEndpoint、ResourceManager、DispatcherRunner;WebMonitorEndpoint主要功能接收来自客户端的请求服务,然后转发到不同的handler处理,比如提交作业submitJob会调用SubmitJobHandler处理。;ResourceManager负责资源的分配和管理;Dispatcher 负责用于接收作业的提交,并进行持久化,生成要执行的作业管理器任务,并在主任务失败时进行恢复,还会会拉起一个JobMaster。

启动过程涉及的核心类及方法

StandaloneSessionClusterEntrypoint.main()->ClusterEntrypoint.runCluster()
具体过程:

public static void main(String[] args) {
        // startup checks and logging
        EnvironmentInformation.logEnvironmentInfo(
                LOG, StandaloneSessionClusterEntrypoint.class.getSimpleName(), args);
        SignalHandler.register(LOG);
        JvmShutdownSafeguard.installAsShutdownHook(LOG);
        //获取配置
        final EntrypointClusterConfiguration entrypointClusterConfiguration =
                ClusterEntrypointUtils.parseParametersOrExit(
                        args,
                        new EntrypointClusterConfigurationParserFactory(),
                        StandaloneSessionClusterEntrypoint.class);
        Configuration configuration = loadConfiguration(entrypointClusterConfiguration);

        StandaloneSessionClusterEntrypoint entrypoint =
                new StandaloneSessionClusterEntrypoint(configuration);
      //启动集群
        ClusterEntrypoint.runClusterEntrypoint(entrypoint);
    }

执行main方法启动集群jobmanager,ClusterEntrypoint.runClusterEntrypoint(entrypoint);

最终会调用ClusterEntrypoint的runCluster()方法:

  private void runCluster(Configuration configuration, PluginManager pluginManager)
            throws Exception {
        synchronized (lock) {
            /**
            *初始化各种服务(6个):
            *commonRpcService 一个基于akka得actorSystem,内部会启动一个actor;主节点启动完会自己给自己发送一个hello消息,最终是有这个service处理的。
            *ioExecutor 专门处理IO的服务。
            *haServices 具体是哪种高可用实现是读取flink-conf.yml配置(high-availability = zookeeper),一般是创建一个zookeeperHaService内部主要使用curator框架。
            *blobServer做大文件的传送服务比如用户作业的jar包,TM上传log文件等
             *heartbeatServices
            */
            initializeServices(configuration, pluginManager);

            // write host information into configuration
            configuration.setString(JobManagerOptions.ADDRESS, commonRpcService.getAddress());
            configuration.setInteger(JobManagerOptions.PORT, commonRpcService.getPort());

            final DispatcherResourceManagerComponentFactory
                    dispatcherResourceManagerComponentFactory =
                            createDispatcherResourceManagerComponentFactory(configuration);
            //创建组件
            clusterComponent =
                    dispatcherResourceManagerComponentFactory.create(
                            configuration,
                            ioExecutor,
                            commonRpcService,
                            haServices,
                            blobServer,
                            heartbeatServices,
                            metricRegistry,
                            archivedExecutionGraphStore,
                            new RpcMetricQueryServiceRetriever(
                                    metricRegistry.getMetricQueryServiceRpcService()),
                            this);

        }
    }

调用DefaultDispatcherResourceManagerComponentFactory.create()创建WebMonitorEndpoint、ResourceManager、Dispatcher;代码如下:

 public DispatcherResourceManagerComponent create(
            Configuration configuration,
            Executor ioExecutor,
            RpcService rpcService,
            HighAvailabilityServices highAvailabilityServices,
            BlobServer blobServer,
            HeartbeatServices heartbeatServices,
            MetricRegistry metricRegistry,
            ArchivedExecutionGraphStore archivedExecutionGraphStore,
            MetricQueryServiceRetriever metricQueryServiceRetriever,
            FatalErrorHandler fatalErrorHandler)
            throws Exception {

        LeaderRetrievalService dispatcherLeaderRetrievalService = null;
        LeaderRetrievalService resourceManagerRetrievalService = null;
        /**
         * TODO 创建三大组件
         */
        WebMonitorEndpoint webMonitorEndpoint = null;
        ResourceManager resourceManager = null;
        DispatcherRunner dispatcherRunner = null;
        ......
      ///返回DispatcherRestEndpoint类型的对象
        webMonitorEndpoint = restEndpointFactory.createRestEndpoint(
                            configuration,
                            dispatcherGatewayRetriever,
                            resourceManagerGatewayRetriever,
                            blobServer,
                            executor,
                            metricFetcher,
                            highAvailabilityServices.getClusterRestEndpointLeaderElectionService(),
                            fatalErrorHandler);

            log.debug("Starting Dispatcher REST endpoint.");
            //TODO 启动的关键方法-重点分析
            webMonitorEndpoint.start();

resourceManager = resourceManagerFactory.createResourceManager(
                            configuration,
                            ResourceID.generate(),
                            rpcService,
                            highAvailabilityServices,
                            heartbeatServices,
                            fatalErrorHandler,
                            new ClusterInformation(hostname, blobServer.getPort()),
                            webMonitorEndpoint.getRestBaseUrl(),
                            metricRegistry,
                            hostname,
                            ioExecutor);

 dispatcherRunner = dispatcherRunnerFactory.createDispatcherRunner(
                            highAvailabilityServices.getDispatcherLeaderElectionService(),
                            fatalErrorHandler,
                            new HaServicesJobGraphStoreFactory(highAvailabilityServices),
                            ioExecutor,
                            rpcService,
                            partialDispatcherServices);

            log.debug("Starting ResourceManager.");
            resourceManager.start();


如上首先初始化各种服务,之后创建三大组件WebMonitorEndpoint、ResourceManager、DispatcherRunner。

分析WebMonitorEndpoint、ResourceManager、DispatcherRunner组件启动过程

WebMonitorEndpoint启动

WebMointorEndpoint类图:

image.png

调用从父类RestServerEndpoint继承的start()方法,start()方法主要作用有3个:1初始化各个handler 2.启动netty服务 3,进行leader选举.

/**
     * Starts this REST server endpoint.
     *
     * @throws Exception if we cannot start the RestServerEndpoint
     */
    public final void start() throws Exception {
      .....
       //1.初始化handler  调用DispatcherRestEndpoint对象的initializeHandlers方法
      handlers = initializeHandlers(restAddressFuture);
      //2.启动netty引导器 ,ServerBootstrap
      bootstrap = new ServerBootstrap();
      //3.启动WebMonitEndpoint  leader选举
      startInternal();
      .....

    }

调用DispatcherRestEndpoint类的initializeHandlers()方法初始化handlers:

protected List> initializeHandlers(
            final CompletableFuture localAddressFuture) {


        /**
         *         //TODO  ChannelInboundHandler channelRead0()方法,这个方法会自动被Netty去调用执行
         *         不管初始的哪个handler,里面都有一个 handlerRequest的方法
         *         channelRead0()的底层,最终调用的就是handler.handleRequest()方法,
         *         当我们提交job的时候,最终由WebMonitorEndpoint 接收到,跳转到JobSubmitHandler来执行
         *         最终执行请求的就是handle Request()方法
         */
        List> handlers =
              //调用父类WebMonitorEndpoint的方法
                super.initializeHandlers(localAddressFuture);

        // Add the Dispatcher specific handlers

        final Time timeout = restConfiguration.getTimeout();
        //处理用户提交作业请求的handler
        JobSubmitHandler jobSubmitHandler =
                new JobSubmitHandler(
                        leaderRetriever, timeout, responseHeaders, executor, clusterConfiguration);

        handlers.add(Tuple2.of(jobSubmitHandler.getMessageHeaders(), jobSubmitHandler));

        return handlers;
    }

调用WebMonitorEndpoint类的startInternal() :


/**
*启动leader选举
*
*/
 public void startInternal() throws Exception {

      //执行leader选举
        leaderElectionService.start(this);
        startExecutionGraphCacheCleanupTask();

        if (hasWebUI) {
            log.info("Web frontend listening at {}.", getRestBaseUrl());
        }
    }

leaderElectionService.start()方法在Flink代码中会经常看到,一般在需要leader选举时都会调用。主要使用Curator框架,leader选举成功将会回调当前类的grantLeadership()方法。
未完待续,下篇将继续分析Dispatcher的创建流程及作用。

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