spark1.1.0源码阅读-executor

1. executor上执行launchTask

  def launchTask(
      context: ExecutorBackend, taskId: Long, taskName: String, serializedTask: ByteBuffer) {
    val tr = new TaskRunner(context, taskId, taskName, serializedTask)
    runningTasks.put(taskId, tr)
    threadPool.execute(tr)
  }

2. executor上执行TaskRunner的run

 class TaskRunner(
      execBackend: ExecutorBackend, val taskId: Long, taskName: String, serializedTask: ByteBuffer)
    extends Runnable {

    @volatile private var killed = false
    @volatile var task: Task[Any] = _
    @volatile var attemptedTask: Option[Task[Any]] = None

    def kill(interruptThread: Boolean) {
      logInfo(s"Executor is trying to kill $taskName (TID $taskId)")
      killed = true
      if (task != null) {
        task.kill(interruptThread)
      }
    }

    override def run() {
      val startTime = System.currentTimeMillis()
      SparkEnv.set(env)
      Thread.currentThread.setContextClassLoader(replClassLoader)
      val ser = SparkEnv.get.closureSerializer.newInstance()
      logInfo(s"Running $taskName (TID $taskId)")
      execBackend.statusUpdate(taskId, TaskState.RUNNING, EMPTY_BYTE_BUFFER)
      var taskStart: Long = 0
      def gcTime = ManagementFactory.getGarbageCollectorMXBeans.map(_.getCollectionTime).sum
      val startGCTime = gcTime

      try {
        SparkEnv.set(env)
        Accumulators.clear()
        val (taskFiles, taskJars, taskBytes) = Task.deserializeWithDependencies(serializedTask)  //反序列化出 taskFiles，taskJars，taskBytes
        updateDependencies(taskFiles, taskJars)
        task = ser.deserialize[Task[Any]](taskBytes, Thread.currentThread.getContextClassLoader)  //反序列化出task对象

        // If this task has been killed before we deserialized it, let's quit now. Otherwise,
        // continue executing the task.
        if (killed) {
          // Throw an exception rather than returning, because returning within a try{} block
          // causes a NonLocalReturnControl exception to be thrown. The NonLocalReturnControl
          // exception will be caught by the catch block, leading to an incorrect ExceptionFailure
          // for the task.
          throw new TaskKilledException
        }

        attemptedTask = Some(task)
        logDebug("Task " + taskId + "'s epoch is " + task.epoch)
        env.mapOutputTracker.updateEpoch(task.epoch)

49         // Run the actual task and measure its runtime.
50         taskStart = System.currentTimeMillis()
51         val value = task.run(taskId.toInt)
52         val taskFinish = System.currentTimeMillis()

        // If the task has been killed, let's fail it.
        if (task.killed) {
          throw new TaskKilledException
        }

3. task.run

private[spark] abstract class Task[T](val stageId: Int, var partitionId: Int) extends Serializable {

  final def run(attemptId: Long): T = {
    context = new TaskContext(stageId, partitionId, attemptId, runningLocally = false)
    context.taskMetrics.hostname = Utils.localHostName()
    taskThread = Thread.currentThread()
    if (_killed) {
      kill(interruptThread = false)
    }
10     runTask(context)
  }

4. task是抽象类，对于具体的类（resultTask和shuffleMapTask）会执行相应的runTask。

a. resultTask

  override def runTask(context: TaskContext): U = {
 2     // Deserialize the RDD and the func using the broadcast variables.
    val ser = SparkEnv.get.closureSerializer.newInstance()
    val (rdd, func) = ser.deserialize[(RDD[T], (TaskContext, Iterator[T]) => U)](
      ByteBuffer.wrap(taskBinary.value), Thread.currentThread.getContextClassLoader)

    metrics = Some(context.taskMetrics)
    try {
      func(context, rdd.iterator(partition, context))
    } finally {
      context.markTaskCompleted()
    }
  }

b. shuffleMapTask

  override def runTask(context: TaskContext): MapStatus = {
    // Deserialize the RDD using the broadcast variable.
    val ser = SparkEnv.get.closureSerializer.newInstance()
    val (rdd, dep) = ser.deserialize[(RDD[_], ShuffleDependency[_, _, _])](
      ByteBuffer.wrap(taskBinary.value), Thread.currentThread.getContextClassLoader)

    metrics = Some(context.taskMetrics)
    var writer: ShuffleWriter[Any, Any] = null
    try {
      val manager = SparkEnv.get.shuffleManager
      writer = manager.getWriter[Any, Any](dep.shuffleHandle, partitionId, context)
12       writer.write(rdd.iterator(partition, context).asInstanceOf[Iterator[_ <: Product2[Any, Any]]])
      return writer.stop(success = true).get
    } catch {
      case e: Exception =>
        if (writer != null) {
          writer.stop(success = false)
        }
        throw e
    } finally {
      context.markTaskCompleted()
    }
  }

  /** Write a bunch of records to this task's output */
  override def write(records: Iterator[_ <: Product2[K, V]]): Unit = {
    val iter = if (dep.aggregator.isDefined) {
      if (dep.mapSideCombine) {
        dep.aggregator.get.combineValuesByKey(records, context)
      } else {
        records
      }
    } else if (dep.aggregator.isEmpty && dep.mapSideCombine) {
      throw new IllegalStateException("Aggregator is empty for map-side combine")
    } else {
      records
    }

    for (elem <- iter) {
      val bucketId = dep.partitioner.getPartition(elem._1)
      shuffle.writers(bucketId).write(elem)
    }
  }

 

 1   /**
 2    * Get a ShuffleWriterGroup for the given map task, which will register it as complete
 3    * when the writers are closed successfully
 4    */
  def forMapTask(shuffleId: Int, mapId: Int, numBuckets: Int, serializer: Serializer,
      writeMetrics: ShuffleWriteMetrics) = {
    new ShuffleWriterGroup {
      shuffleStates.putIfAbsent(shuffleId, new ShuffleState(numBuckets))
      private val shuffleState = shuffleStates(shuffleId)
      private var fileGroup: ShuffleFileGroup = null

      val writers: Array[BlockObjectWriter] = if (consolidateShuffleFiles) {
        fileGroup = getUnusedFileGroup()
        Array.tabulate[BlockObjectWriter](numBuckets) { bucketId =>
          val blockId = ShuffleBlockId(shuffleId, mapId, bucketId)
          blockManager.getDiskWriter(blockId, fileGroup(bucketId), serializer, bufferSize,
            writeMetrics)
        }
      } else {
        Array.tabulate[BlockObjectWriter](numBuckets) { bucketId =>
          val blockId = ShuffleBlockId(shuffleId, mapId, bucketId)
          val blockFile = blockManager.diskBlockManager.getFile(blockId)
          // Because of previous failures, the shuffle file may already exist on this machine.
          // If so, remove it.
          if (blockFile.exists) {
            if (blockFile.delete()) {
              logInfo(s"Removed existing shuffle file $blockFile")
            } else {
              logWarning(s"Failed to remove existing shuffle file $blockFile")
            }
          }
          blockManager.getDiskWriter(blockId, blockFile, serializer, bufferSize, writeMetrics)
        }
      }