Spark源码分析之SparkSubmit的流程-优快云博客

本文链接：https://blog.youkuaiyun.com/SmallCatBaby/article/details/92995036

本文详细分析了SparkSubmit的源码，从启动脚本开始，讲解了SparkSubmit如何根据部署模式选择不同的childMainClass，以及在不同模式下如何启动Driver。通过解析参数、构建环境、启动主类，最后深入到Driver启动的细节，包括JVM钩子、远程拷贝jar、启动process等步骤。

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准备

本文主要对SparkSubmit的任务提交流程源码进行分析。Spark源码版本为2.3.1。

首先阅读一下启动脚本，看看首先加载的是哪个类，我们看一下spark-submit启动脚本中的具体内容。

spark-submit的shell脚本

可以看到这里加载的类是org.apache.spark.deploy.SparkSubmit，并且把启动相关的参数也带过去了。下面我们跟一下源码看看整个流程是如何运作的...

流程分析

SparkSubmit的main方法如下

//提交任务主类运行
  override def main(args: Array[String]): Unit = {
    // Initialize logging if it hasn't been done yet. Keep track of whether logging needs to
    // be reset before the application starts.
    val uninitLog = initializeLogIfNecessary(true, silent = true)
    //设置参数
    val appArgs = new SparkSubmitArguments(args)
    if (appArgs.verbose) {
      // scalastyle:off println
      printStream.println(appArgs)
      // scalastyle:on println
    }
    appArgs.action match {
      //任务提交匹配 submit
      case SparkSubmitAction.SUBMIT => submit(appArgs, uninitLog)
      case SparkSubmitAction.KILL => kill(appArgs)
      case SparkSubmitAction.REQUEST_STATUS => requestStatus(appArgs)
    }
  }

这里我们由于我们是提交作业，所有会走上面的submit(appArgs, uninitLog)方法

private def submit(args: SparkSubmitArguments, uninitLog: Boolean): Unit = {
    //以下方法prepareSubmitEnvironment 返回四元组，重点注意childMainClass类 这里以standalone-cluster为例
    val (childArgs, childClasspath, sparkConf, childMainClass) = prepareSubmitEnvironment(args)
   
    def doRunMain(): Unit = {... }

    ...
}

可以看到submit方法首先会准备任务提交的环境，调用了prepareSubmitEnvironment，该方法会返回四元组，该方法中会调用doPrepareSubmitEnvironment，这里我们重点注意childMainClass类具体是什么，因为这里涉及到后面启动我们主类的过程。

以下是doPrepareSubmitEnvironment方法的源码...

 private def doPrepareSubmitEnvironment(
      args: SparkSubmitArguments,
      conf: Option[HadoopConfiguration] = None)
      : (Seq[String], Seq[String], SparkConf, String) = {
    // Return values
    val childArgs = new ArrayBuffer[String]()
    val childClasspath = new ArrayBuffer[String]()
    val sparkConf = new SparkConf()
    var childMainClass = ""

   val clusterManager: Int = args.master match {
      case "yarn" => YARN
      case "yarn-client" | "yarn-cluster" =>
        printWarning(s"Master ${args.master} is deprecated since 2.0." +
          " Please use master \"yarn\" with specified deploy mode instead.")
        YARN
      case m if m.startsWith("spark") => STANDALONE
      case m if m.startsWith("mesos") => MESOS
      case m if m.startsWith("k8s") => KUBERNETES
      case m if m.startsWith("local") => LOCAL
      case _ =>
        printErrorAndExit("Master must either be yarn or start with spark, mesos, k8s, or local")
        -1
  }
    // Set the deploy mode; default is client mode
    var deployMode: Int = args.deployMode match {
      case "client" | null => CLIENT
      case "cluster" => CLUSTER
      case _ => printErrorAndExit("Deploy mode must be either client or cluster"); -1
    }
   ....
  if (deployMode == CLIENT) {
      childMainClass = args.mainClass
      if (localPrimaryResource != null && isUserJar(localPrimaryResource)) {
        childClasspath += localPrimaryResource
      }
      if (localJars != null) { childClasspath ++= localJars.split(",") }
    }
....
// In standalone cluster mode, use the REST client to submit the application (Spark 1.3+).
    // All Spark parameters are expected to be passed to the client through system properties.
    //standalone-cluster模式
    if (args.isStandaloneCluster) {
      //使用rest风格，这里rest提交是指使用json 格式和http 提交任务 ，spark1.3+支持
      if (args.useRest) {
        childMainClass = REST_CLUSTER_SUBMIT_CLASS
        childArgs += (args.primaryResource, args.mainClass)
      } else {
        //正常提交方式
        // In legacy standalone cluster mode, use Client as a wrapper around the user class
        childMainClass = STANDALONE_CLUSTER_SUBMIT_CLASS
        if (args.supervise) { childArgs += "--supervise" }
        Option(args.driverMemory).foreach { m => childArgs += ("--memory", m) }
        Option(args.driverCores).foreach { c => childArgs += ("--cores", c) }
        childArgs += "launch"
        childArgs += (args.master, args.primaryResource, args.mainClass)
      }
      if (args.childArgs != null) {
        childArgs ++= args.childArgs
      }
    }
....