spark core 2.0 Executor Heartbeat

Executor heartbeat 调度一个任务向driver汇报心跳和部分度量信息

  /**
   * Schedules a task to report heartbeat and partial metrics for active tasks to driver.
   */
  private def startDriverHeartbeater(): Unit = {
    val intervalMs = conf.getTimeAsMs("spark.executor.heartbeatInterval", "10s")

    // Wait a random interval so the heartbeats don't end up in sync
    val initialDelay = intervalMs + (math.random * intervalMs).asInstanceOf[Int]

    val heartbeatTask = new Runnable() {
      override def run(): Unit = Utils.logUncaughtExceptions(reportHeartBeat())
    }
    heartbeater.scheduleAtFixedRate(heartbeatTask, initialDelay, intervalMs, TimeUnit.MILLISECONDS)
  }
}

heartbeater是一个后台周期性的执行器。周期性的调用heartbeatTask这个任务。

  private val heartbeater = ThreadUtils.newDaemonSingleThreadScheduledExecutor("driver-heartbeater")

heartbeatTask仅调用reportHeartBeat方法，如下

/** Reports heartbeat and metrics for active tasks to the driver. */
  private def reportHeartBeat(): Unit = {
    // list of (task id, accumUpdates) to send back to the driver
    val accumUpdates = new ArrayBuffer[(Long, Seq[AccumulatorV2[_, _]])]()
    val curGCTime = computeTotalGcTime()

    for (taskRunner <- runningTasks.values().asScala) {
      if (taskRunner.task != null) {
        taskRunner.task.metrics.mergeShuffleReadMetrics()
        taskRunner.task.metrics.setJvmGCTime(curGCTime - taskRunner.startGCTime)
        accumUpdates += ((taskRunner.taskId, taskRunner.task.metrics.accumulators()))
      }
    }

    val message = Heartbeat(executorId, accumUpdates.toArray, env.blockManager.blockManagerId)
    try {
      val response = heartbeatReceiverRef.askWithRetry[HeartbeatResponse](
          message, RpcTimeout(conf, "spark.executor.heartbeatInterval", "10s"))
      if (response.reregisterBlockManager) {
        logInfo("Told to re-register on heartbeat")
        env.blockManager.reregister()
      }
      heartbeatFailures = 0
    } catch {
      case NonFatal(e) =>
        logWarning("Issue communicating with driver in heartbeater", e)
        heartbeatFailures += 1
        if (heartbeatFailures >= HEARTBEAT_MAX_FAILURES) {
          logError(s"Exit as unable to send heartbeats to driver " +
            s"more than $HEARTBEAT_MAX_FAILURES times")
          System.exit(ExecutorExitCode.HEARTBEAT_FAILURE)
        }
    }
  }