spark scheduler

1 生成DAG 依赖图

private def createResultStage(
  rdd: RDD[_],
  func: (TaskContext, Iterator[_]) => _,
  partitions: Array[Int],
  jobId: Int,
  callSite: CallSite): ResultStage = {
val (shuffleDeps, resourceProfiles) = getShuffleDependenciesAndResourceProfiles(rdd)
val resourceProfile = mergeResourceProfilesForStage(resourceProfiles)
checkBarrierStageWithDynamicAllocation(rdd)
checkBarrierStageWithNumSlots(rdd, resourceProfile)
checkBarrierStageWithRDDChainPattern(rdd, partitions.toSet.size)
val parents = getOrCreateParentStages(shuffleDeps, jobId)
val id = nextStageId.getAndIncrement()
val stage = new ResultStage(id, rdd, func, partitions, parents, jobId,
  callSite, resourceProfile.id)
stageIdToStage(id) = stage
updateJobIdStageIdMaps(jobId, stage)
stage

}
2 提交阶段

	/** Submits stage, but first recursively submits any missing parents. */
  private def submitStage(stage: Stage): Unit = {
    val jobId = activeJobForStage(stage)
    if (jobId.isDefined) {
      logDebug(s"submitStage($stage (name=${stage.name};" +
        s"jobs=${stage.jobIds.toSeq.sorted.mkString(",")}))")
      if (!waitingStages(stage) && !runningStages(stage) && !failedStages(stage)) {
        val missing = getMissingParentStages(stage).sortBy(_.id)
        logDebug("missing: " + missing)
        if (missing.isEmpty) {
          logInfo("Submitting " + stage + " (" + stage.rdd + "), which has no missing parents")
          submitMissingTasks(stage, jobId.get)
        } else {
          for (parent <- missing) {
            submitStage(parent)
          }
          waitingStages += stage
        }
      }
    } else {
      abortStage(stage, "No active job for stage " + stage.id, None)
    }
  }

先提交依赖parent stage，再提交final stage