Spark-源码分析01-Luanch Driver

1.SparkSubmit.scala

什么是Driver 呢？其实application运行的进程 就是driver，也是我们所写的代码就是Driver。

object DefaultPartitionsNum {

  def main(args: Array[String]): Unit = {
    val spark = SparkSession.builder().master("local[*]").getOrCreate()
    val rdd1 = spark.sparkContext.textFile("path")
    rdd1.collect()
  }
}

当我们执行这段代码或者通过spark-submit提交这个application时，这段代码执行时就会启动一个Driver。而Driver的入口就是在SparkContext 中。

下面就是通过 spark-submit 提交时的源码分析

 

 

 

主要调用M-prepareSubmitEnvironment，该方法更根据用户定义的参数，匹配不同client，去调用不同clientApp。(ps：本次讲ClientApp  也就是standalone)

在M-runMain通过  调用M-Utils.classForName 反射的方式调用 ClientApp 的 M-main （ps:如果是localhost 或者是client 直接反射用户的定义的main）

几种提交方式

// Following constants are visible for testing.
private[deploy] val YARN_CLUSTER_SUBMIT_CLASS = "org.apache.spark.deploy.yarn.YarnClusterApplication"
private[deploy] val REST_CLUSTER_SUBMIT_CLASS = classOf[RestSubmissionClientApp].getName()
private[deploy] val STANDALONE_CLUSTER_SUBMIT_CLASS = classOf[ClientApp].getName()
private[deploy] val KUBERNETES_CLUSTER_SUBMIT_CLASS ="org.apache.spark.deploy.k8s.submit.KubernetesClientApplication"

private[deploy] def prepareSubmitEnvironment(
    args: SparkSubmitArguments,
    conf: Option[HadoopConfiguration] = None)
    : (Seq[String], Seq[String], SparkConf, String)

 

 

2.ClientApp.scala   

最后driver粗粒度就是DriverWrapper

通过Rpc 发送给driver

override def onStart(): Unit = {
  driverArgs.cmd match {
    case "launch" =>
      val mainClass = "org.apache.spark.deploy.worker.DriverWrapper"
      asyncSendToMasterAndForwardReply[SubmitDriverResponse](RequestSubmitDriver(driverDescription))

 

 

3.Master.scala

master 接受之后，放入map缓存中，调用M-schedule，根据资源选择一个work，向该work发送启动LaunchDriver的消息

case RequestSubmitDriver(description) =>
  if (state != RecoveryState.ALIVE) {
    val msg = s"${Utils.BACKUP_STANDALONE_MASTER_PREFIX}: $state. " +
      "Can only accept driver submissions in ALIVE state."
    context.reply(SubmitDriverResponse(self, false, None, msg))
  } else {
    logInfo("Driver submitted " + description.command.mainClass)
    val driver = createDriver(description)
    persistenceEngine.addDriver(driver)
    waitingDrivers += driver
    drivers.add(driver)
    schedule()
    // TODO: It might be good to instead have the submission client poll the master to determine
    //       the current status of the driver. For now it's simply "fire and forget".
    context.reply(SubmitDriverResponse(self, true, Some(driver.id),
      s"Driver successfully submitted as ${driver.id}"))
  }
}

private def schedule(): Unit = {
  if (state != RecoveryState.ALIVE) {
    return
  }
  // Drivers take strict precedence over executors
  val shuffledAliveWorkers = Random.shuffle(workers.toSeq.filter(_.state == WorkerState.ALIVE))
  val numWorkersAlive = shuffledAliveWorkers.size
  var curPos = 0
  for (driver <- waitingDrivers.toList) { // iterate over a copy of waitingDrivers
    // We assign workers to each waiting driver in a round-robin fashion. For each driver, we
    // start from the last worker that was assigned a driver, and continue onwards until we have
    // explored all alive workers.
    var launched = false
    var numWorkersVisited = 0
    while (numWorkersVisited < numWorkersAlive && !launched) {
      val worker = shuffledAliveWorkers(curPos)
      numWorkersVisited += 1
      if (worker.memoryFree >= driver.desc.mem && worker.coresFree >= driver.desc.cores) {
        launchDriver(worker, driver)
        waitingDrivers -= driver
        launched = true
      }
      curPos = (curPos + 1) % numWorkersAlive
    }
  }
  startExecutorsOnWorkers()
}

private def launchDriver(worker: WorkerInfo, driver: DriverInfo) {
  logInfo("Launching driver " + driver.id + " on worker " + worker.id)
  worker.addDriver(driver)
  driver.worker = Some(worker)
  worker.endpoint.send(LaunchDriver(driver.id, driver.desc))
  driver.state = DriverState.RUNNING
}

 

 

4.Work.scala

work接受消息之后，new DriverRunner() 调用该对象的M-start

case LaunchDriver(driverId, driverDesc) =>
  logInfo(s"Asked to launch driver $driverId")
  val driver = new DriverRunner(
    conf,
    driverId,
    workDir,
    sparkHome,
    driverDesc.copy(command = Worker.maybeUpdateSSLSettings(driverDesc.command, conf)),
    self,
    workerUri,
    securityMgr)
  drivers(driverId) = driver
  driver.start()

 

 

5.DriverRunner.scala

该对象中，M-start 中new 了一个线程，调用prepareAndRunDriver 最后通过 ProcessBuilder调用 DriverWrapper 的main（step2中的）

 

private[worker] def start() = {
  new Thread("DriverRunner for " + driverId) {
    override def run() {
      var shutdownHook: AnyRef = null
      try {
        shutdownHook = ShutdownHookManager.addShutdownHook { () =>
          logInfo(s"Worker shutting down, killing driver $driverId")
          kill()
        }
        // prepare driver jars and run driver
        val exitCode = prepareAndRunDriver()
        // set final state depending on if forcibly killed and process exit code
        finalState = if (exitCode == 0) {
          Some(DriverState.FINISHED)
        } else if (killed) {
          Some(DriverState.KILLED)
        } else {
          Some(DriverState.FAILED)
        }
      } catch {
        case e: Exception =>
          kill()
          finalState = Some(DriverState.ERROR)
          finalException = Some(e)
      } finally {
        if (shutdownHook != null) {
          ShutdownHookManager.removeShutdownHook(shutdownHook)
        }
      }
      // notify worker of final driver state, possible exception
      worker.send(DriverStateChanged(driverId, finalState.get, finalException))
    }
  }.start()
}

private[worker] def prepareAndRunDriver(): Int = {
  val driverDir = createWorkingDirectory()
  val localJarFilename = downloadUserJar(driverDir)
  def substituteVariables(argument: String): String = argument match {
    case "{{WORKER_URL}}" => workerUrl
    case "{{USER_JAR}}" => localJarFilename
    case other => other
  }
  // TODO: If we add ability to submit multiple jars they should also be added here
  val builder = CommandUtils.buildProcessBuilder(driverDesc.command, securityManager,
    driverDesc.mem, sparkHome.getAbsolutePath, substituteVariables)
  runDriver(builder, driverDir, driverDesc.supervise)
}

private[worker] def prepareAndRunDriver(): Int = {
  val driverDir = createWorkingDirectory()
  val localJarFilename = downloadUserJar(driverDir)
  def substituteVariables(argument: String): String = argument match {
    case "{{WORKER_URL}}" => workerUrl
    case "{{USER_JAR}}" => localJarFilename
    case other => other
  }
  // TODO: If we add ability to submit multiple jars they should also be added here
  val builder = CommandUtils.buildProcessBuilder(driverDesc.command, securityManager,
    driverDesc.mem, sparkHome.getAbsolutePath, substituteVariables)
  runDriver(builder, driverDir, driverDesc.supervise)
}

6.DriverWrapper.scala （粗粒度Driver client)
开始调用用户指定 jar 和main 真正开始执行我们所写的代码
def main(args: Array[String]) {
  args.toList match {
    /*
     * IMPORTANT: Spark 1.3 provides a stable application submission gateway that is both
     * backward and forward compatible across future Spark versions. Because this gateway
     * uses this class to launch the driver, the ordering and semantics of the arguments
     * here must also remain consistent across versions.
     */
    case workerUrl :: userJar :: mainClass :: extraArgs =>
      val conf = new SparkConf()
      val host: String = Utils.localHostName()
      val port: Int = sys.props.getOrElse("spark.driver.port", "0").toInt
      val rpcEnv = RpcEnv.create("Driver", host, port, conf, new SecurityManager(conf))
      logInfo(s"Driver address: ${rpcEnv.address}")
      rpcEnv.setupEndpoint("workerWatcher", new WorkerWatcher(rpcEnv, workerUrl))

      val currentLoader = Thread.currentThread.getContextClassLoader
      val userJarUrl = new File(userJar).toURI().toURL()
      val loader =
        if (sys.props.getOrElse("spark.driver.userClassPathFirst", "false").toBoolean) {
          new ChildFirstURLClassLoader(Array(userJarUrl), currentLoader)
        } else {
          new MutableURLClassLoader(Array(userJarUrl), currentLoader)
        }
      Thread.currentThread.setContextClassLoader(loader)
      setupDependencies(loader, userJar)

      // Delegate to supplied main class
      val clazz = Utils.classForName(mainClass)
      val mainMethod = clazz.getMethod("main", classOf[Array[String]])
      mainMethod.invoke(null, extraArgs.toArray[String])
      rpcEnv.shutdown()
    case _ =>
      // scalastyle:off println
      System.err.println("Usage: DriverWrapper <workerUrl> <userJar> <driverMainClass> [options]")
      // scalastyle:on println
      System.exit(-1)
  }
}