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原始碼-spark執行流程分析

private def createTaskScheduler(
      sc: SparkContext,
      master: String): (SchedulerBackend, TaskScheduler) = {
    import SparkMasterRegex._

    // When running locally, don't try to re-execute tasks on failure.
    val MAX_LOCAL_TASK_FAILURES = 1

    master match {
      case "local" =>
        val scheduler = new TaskSchedulerImpl(sc, MAX_LOCAL_TASK_FAILURES, isLocal = true)
        val backend = new LocalBackend(sc.getConf, scheduler, 1)
        scheduler.initialize(backend)
        (backend, scheduler)

      case LOCAL_N_REGEX(threads) =>
        def localCpuCount: Int = Runtime.getRuntime.availableProcessors()
        // local[*] estimates the number of cores on the machine; local[N] uses exactly N threads.
        val threadCount = if (threads == "*") localCpuCount else threads.toInt
        if (threadCount <= 0) {
          throw new SparkException(s"Asked to run locally with $threadCount threads")
        }
        val scheduler = new TaskSchedulerImpl(sc, MAX_LOCAL_TASK_FAILURES, isLocal = true)
        val backend = new LocalBackend(sc.getConf, scheduler, threadCount)
        scheduler.initialize(backend)
        (backend, scheduler)

      case LOCAL_N_FAILURES_REGEX(threads, maxFailures) =>
        def localCpuCount: Int = Runtime.getRuntime.availableProcessors()
        // local[*, M] means the number of cores on the computer with M failures
        // local[N, M] means exactly N threads with M failures
        val threadCount = if (threads == "*") localCpuCount else threads.toInt
        val scheduler = new TaskSchedulerImpl(sc, maxFailures.toInt, isLocal = true)
        val backend = new LocalBackend(sc.getConf, scheduler, threadCount)
        scheduler.initialize(backend)
        (backend, scheduler)

      case SPARK_REGEX(sparkUrl) =>
        val scheduler = new TaskSchedulerImpl(sc)
        val masterUrls = sparkUrl.split(",").map("spark://" + _)
        val backend = new SparkDeploySchedulerBackend(scheduler, sc, masterUrls)
        scheduler.initialize(backend)
        (backend, scheduler)

      case LOCAL_CLUSTER_REGEX(numSlaves, coresPerSlave, memoryPerSlave) =>
        // Check to make sure memory requested <= memoryPerSlave. Otherwise Spark will just hang.
        val memoryPerSlaveInt = memoryPerSlave.toInt
        if (sc.executorMemory > memoryPerSlaveInt) {
          throw new SparkException(
            "Asked to launch cluster with %d MB RAM / worker but requested %d MB/worker".format(
              memoryPerSlaveInt, sc.executorMemory))
        }

        val scheduler = new TaskSchedulerImpl(sc)
        val localCluster = new LocalSparkCluster(
          numSlaves.toInt, coresPerSlave.toInt, memoryPerSlaveInt, sc.conf)
        val masterUrls = localCluster.start()
        val backend = new SparkDeploySchedulerBackend(scheduler, sc, masterUrls)
        scheduler.initialize(backend)
        backend.shutdownCallback = (backend: SparkDeploySchedulerBackend) => {
          localCluster.stop()
        }
        (backend, scheduler)

      case "yarn-standalone" | "yarn-cluster" =>
        if (master == "yarn-standalone") {
          logWarning(
            "\"yarn-standalone\" is deprecated as of Spark 1.0. Use \"yarn-cluster\" instead.")
        }
        val scheduler = try {
          val clazz = Utils.classForName("org.apache.spark.scheduler.cluster.YarnClusterScheduler")
          val cons = clazz.getConstructor(classOf[SparkContext])
          cons.newInstance(sc).asInstanceOf[TaskSchedulerImpl]
        } catch {
          // TODO: Enumerate the exact reasons why it can fail
          // But irrespective of it, it means we cannot proceed !
          case e: Exception => {
            throw new SparkException("YARN mode not available ?", e)
          }
        }
        val backend = try {
          val clazz =
            Utils.classForName("org.apache.spark.scheduler.cluster.YarnClusterSchedulerBackend")
          val cons = clazz.getConstructor(classOf[TaskSchedulerImpl], classOf[SparkContext])
          cons.newInstance(scheduler, sc).asInstanceOf[CoarseGrainedSchedulerBackend]
        } catch {
          case e: Exception => {
            throw new SparkException("YARN mode not available ?", e)
          }
        }
        scheduler.initialize(backend)
        (backend, scheduler)

      case "yarn-client" =>
        val scheduler = try {
          val clazz = Utils.classForName("org.apache.spark.scheduler.cluster.YarnScheduler")
          val cons = clazz.getConstructor(classOf[SparkContext])
          cons.newInstance(sc).asInstanceOf[TaskSchedulerImpl]

        } catch {
          case e: Exception => {
            throw new SparkException("YARN mode not available ?", e)
          }
        }

        val backend = try {
          val clazz =
            Utils.classForName("org.apache.spark.scheduler.cluster.YarnClientSchedulerBackend")
          val cons = clazz.getConstructor(classOf[TaskSchedulerImpl], classOf[SparkContext])
          cons.newInstance(scheduler, sc).asInstanceOf[CoarseGrainedSchedulerBackend]
        } catch {
          case e: Exception => {
            throw new SparkException("YARN mode not available ?", e)
          }
        }

        scheduler.initialize(backend)
        (backend, scheduler)

      case MESOS_REGEX(mesosUrl) =>
        MesosNativeLibrary.load()
        val scheduler = new TaskSchedulerImpl(sc)
        val coarseGrained = sc.conf.getBoolean("spark.mesos.coarse", defaultValue = true)
        val backend = if (coarseGrained) {
          new CoarseMesosSchedulerBackend(scheduler, sc, mesosUrl, sc.env.securityManager)
        } else {
          new MesosSchedulerBackend(scheduler, sc, mesosUrl)
        }
        scheduler.initialize(backend)
        (backend, scheduler)

      case SIMR_REGEX(simrUrl) =>
        val scheduler = new TaskSchedulerImpl(sc)
        val backend = new SimrSchedulerBackend(scheduler, sc, simrUrl)
        scheduler.initialize(backend)
        (backend, scheduler)

      case zkUrl if zkUrl.startsWith("zk://") =>
        logWarning("Master URL for a multi-master Mesos cluster managed by ZooKeeper should be " +
          "in the form mesos://zk://host:port. Current Master URL will stop working in Spark 2.0.")
        createTaskScheduler(sc, "mesos://" + zkUrl)

      case _ =>
        throw new SparkException("Could not parse Master URL: '" + master + "'")
    }
  }
}