Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/4155#discussion_r23434036
--- Diff:
core/src/main/scala/org/apache/spark/scheduler/OutputCommitCoordinator.scala ---
@@ -0,0 +1,172 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.scheduler
+
+import scala.collection.mutable
+import scala.concurrent.duration.FiniteDuration
+
+import akka.actor.{PoisonPill, ActorRef, Actor}
+
+import org.apache.spark.{SparkConf, Logging}
+import org.apache.spark.util.{AkkaUtils, ActorLogReceive}
+
+private[spark] sealed trait OutputCommitCoordinationMessage extends
Serializable
+
+private[spark] case class StageStarted(stage: Int) extends
OutputCommitCoordinationMessage
+private[spark] case class StageEnded(stage: Int) extends
OutputCommitCoordinationMessage
+private[spark] case object StopCoordinator extends
OutputCommitCoordinationMessage
+
+private[spark] case class AskPermissionToCommitOutput(
+ stage: Int,
+ task: Long,
+ taskAttempt: Long)
+ extends OutputCommitCoordinationMessage
+
+private[spark] case class TaskCompleted(
+ stage: Int,
+ task: Long,
+ attempt: Long,
+ successful: Boolean)
+ extends OutputCommitCoordinationMessage
+
+/**
+ * Authority that decides whether tasks can commit output to HDFS.
+ *
+ * This lives on the driver, but the actor allows the tasks that commit
+ * to Hadoop to invoke it.
+ */
+private[spark] class OutputCommitCoordinator(conf: SparkConf) extends
Logging {
+
+ // Initialized by SparkEnv
+ var coordinatorActor: ActorRef = _
+ val timeout = AkkaUtils.askTimeout(conf)
+ val maxAttempts = AkkaUtils.numRetries(conf)
+ val retryInterval = AkkaUtils.retryWaitMs(conf)
+
+ private type StageId = Int
+ private type TaskId = Long
+ private type TaskAttemptId = Long
+
+ private val authorizedCommittersByStage:
+ mutable.Map[StageId, mutable.Map[TaskId, TaskAttemptId]] =
mutable.HashMap()
+
+ def stageStart(stage: StageId) {
+ coordinatorActor ! StageStarted(stage)
+ }
+ def stageEnd(stage: StageId) {
+ coordinatorActor ! StageEnded(stage)
+ }
+
+ def canCommit(
+ stage: StageId,
+ task: TaskId,
+ attempt: TaskAttemptId): Boolean = {
+ AkkaUtils.askWithReply(AskPermissionToCommitOutput(stage, task,
attempt),
+ coordinatorActor, maxAttempts, retryInterval, timeout)
+ }
+
+ def taskCompleted(
+ stage: StageId,
+ task: TaskId,
+ attempt: TaskAttemptId,
+ successful: Boolean) {
+ coordinatorActor ! TaskCompleted(stage, task, attempt, successful)
+ }
+
+ def stop() {
+ val stopped = AkkaUtils.askWithReply[Boolean](StopCoordinator,
coordinatorActor, timeout)
+ if (!stopped) {
+ logWarning("Expected true from stopping output coordinator actor,
but got false!")
+ }
+ authorizedCommittersByStage.foreach(_._2.clear)
+ authorizedCommittersByStage.clear
+ }
+
+ private def handleStageStart(stage: StageId): Unit = {
+ authorizedCommittersByStage(stage) = mutable.HashMap[TaskId,
TaskAttemptId]()
+ }
+
+ private def handleStageEnd(stage: StageId): Unit = {
+ authorizedCommittersByStage.remove(stage)
+ }
+
+ private def handleAskPermissionToCommit(
+ stage: StageId,
+ task: TaskId,
+ attempt: TaskAttemptId):
+ Boolean = {
+ if (!authorizedCommittersByStage.contains(stage)) {
+ logDebug(s"Stage $stage has completed, so not allowing task attempt
$attempt to commit")
+ return false
+ }
+ val authorizedCommitters = authorizedCommittersByStage(stage)
+ if (authorizedCommitters.contains(task)) {
+ val existingCommitter = authorizedCommitters(task)
+ logDebug(s"Denying $attempt to commit for stage=$stage, task=$task;
" +
+ s"existingCommitter = $existingCommitter")
+ false
+ } else {
+ logDebug(s"Authorizing $attempt to commit for stage=$stage,
task=$task")
+ authorizedCommitters(task) = attempt
+ true
+ }
+ }
+
+ private def handleTaskCompletion(
+ stage: StageId,
+ task: TaskId,
+ attempt: TaskAttemptId,
+ successful: Boolean): Unit = {
+ if (!authorizedCommittersByStage.contains(stage)) {
+ logDebug(s"Ignoring task completion for completed stage")
+ return
+ }
+ val authorizedCommitters = authorizedCommittersByStage(stage)
+ if (authorizedCommitters.get(task) == Some(attempt) && !successful) {
+ logDebug(s"Authorized committer $attempt (stage=$stage, task=$task)
failed; clearing lock")
+ // The authorized committer failed; clear the lock so future
attempts can commit their output
+ authorizedCommitters.remove(task)
+ }
+ }
+
+}
+
+private[spark] object OutputCommitCoordinator {
+
+ class OutputCommitCoordinatorActor(outputCommitCoordinator:
OutputCommitCoordinator)
--- End diff --
What's the motivation for defining this class inside of the
`OutputCommitCoordinator` and having a `createActor` method instead of a
regular constructor call?
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