[SPARK-24589][CORE] Correctly identify tasks in output commit coordinator.

When an output stage is retried, it's possible that tasks from the previous
attempt are still running. In that case, there would be a new task for the
same partition in the new attempt, and the coordinator would allow both
tasks to commit their output since it did not keep track of stage attempts.

The change adds more information to the stage state tracked by the coordinator,
so that only one task is allowed to commit the output in the above case.
The stage state in the coordinator is also maintained across stage retries,
so that a stray speculative task from a previous stage attempt is not allowed
to commit.

This also removes some code added in SPARK-18113 that allowed for duplicate
commit requests; with the RPC code used in Spark 2, that situation cannot
happen, so there is no need to handle it.

Author: Marcelo Vanzin <[email protected]>

Closes apache#21577 from vanzin/SPARK-24552.

Author: Marcelo Vanzin

core/src/main/scala/org/apache/spark/mapred/SparkHadoopMapRedUtil.scala

@@ -69,9 +69,9 @@ object SparkHadoopMapRedUtil extends Logging {
 
       if (shouldCoordinateWithDriver) {
         val outputCommitCoordinator = SparkEnv.get.outputCommitCoordinator
-        val taskAttemptNumber = TaskContext.get().attemptNumber()
-        val stageId = TaskContext.get().stageId()
-        val canCommit = outputCommitCoordinator.canCommit(stageId, splitId, taskAttemptNumber)
+        val ctx = TaskContext.get()
+        val canCommit = outputCommitCoordinator.canCommit(ctx.stageId(), ctx.stageAttemptNumber(),
+          splitId, ctx.attemptNumber())
 
         if (canCommit) {
           performCommit()
@@ -81,7 +81,7 @@ object SparkHadoopMapRedUtil extends Logging {
           logInfo(message)
           // We need to abort the task so that the driver can reschedule new attempts, if necessary
           committer.abortTask(mrTaskContext)
-          throw new CommitDeniedException(message, stageId, splitId, taskAttemptNumber)
+          throw new CommitDeniedException(message, ctx.stageId(), splitId, ctx.attemptNumber())
         }
       } else {
         // Speculation is disabled or a user has chosen to manually bypass the commit coordination

core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala

@@ -1171,6 +1171,7 @@ class DAGScheduler(
 
     outputCommitCoordinator.taskCompleted(
       stageId,
+      task.stageAttemptId,
       task.partitionId,
       event.taskInfo.attemptNumber, // this is a task attempt number
       event.reason)
@@ -1330,23 +1331,24 @@ class DAGScheduler(
             s" ${task.stageAttemptId} and there is a more recent attempt for that stage " +
             s"(attempt ${failedStage.latestInfo.attemptNumber}) running")
         } else {
+          failedStage.fetchFailedAttemptIds.add(task.stageAttemptId)
+          val shouldAbortStage =
+            failedStage.fetchFailedAttemptIds.size >= maxConsecutiveStageAttempts ||
+            disallowStageRetryForTest
+
           // It is likely that we receive multiple FetchFailed for a single stage (because we have
           // multiple tasks running concurrently on different executors). In that case, it is
           // possible the fetch failure has already been handled by the scheduler.
           if (runningStages.contains(failedStage)) {
             logInfo(s"Marking $failedStage (${failedStage.name}) as failed " +
               s"due to a fetch failure from $mapStage (${mapStage.name})")
-            markStageAsFinished(failedStage, Some(failureMessage))
+            markStageAsFinished(failedStage, errorMessage = Some(failureMessage),
+              willRetry = !shouldAbortStage)
           } else {
             logDebug(s"Received fetch failure from $task, but its from $failedStage which is no " +
               s"longer running")
           }
 
-          failedStage.fetchFailedAttemptIds.add(task.stageAttemptId)
-          val shouldAbortStage =
-            failedStage.fetchFailedAttemptIds.size >= maxConsecutiveStageAttempts ||
-            disallowStageRetryForTest
-
           if (shouldAbortStage) {
             val abortMessage = if (disallowStageRetryForTest) {
               "Fetch failure will not retry stage due to testing config"
@@ -1545,7 +1547,10 @@ class DAGScheduler(
   /**
    * Marks a stage as finished and removes it from the list of running stages.
    */
-  private def markStageAsFinished(stage: Stage, errorMessage: Option[String] = None): Unit = {
+  private def markStageAsFinished(
+      stage: Stage,
+      errorMessage: Option[String] = None,
+      willRetry: Boolean = false): Unit = {
     val serviceTime = stage.latestInfo.submissionTime match {
       case Some(t) => "%.03f".format((clock.getTimeMillis() - t) / 1000.0)
       case _ => "Unknown"
@@ -1564,7 +1569,9 @@ class DAGScheduler(
       logInfo(s"$stage (${stage.name}) failed in $serviceTime s due to ${errorMessage.get}")
     }
 
-    outputCommitCoordinator.stageEnd(stage.id)
+    if (!willRetry) {
+      outputCommitCoordinator.stageEnd(stage.id)
+    }
     listenerBus.post(SparkListenerStageCompleted(stage.latestInfo))
     runningStages -= stage
   }

core/src/main/scala/org/apache/spark/scheduler/OutputCommitCoordinator.scala

@@ -27,7 +27,11 @@ import org.apache.spark.util.{RpcUtils, ThreadUtils}
 private sealed trait OutputCommitCoordinationMessage extends Serializable
 
 private case object StopCoordinator extends OutputCommitCoordinationMessage
-private case class AskPermissionToCommitOutput(stage: Int, partition: Int, attemptNumber: Int)
+private case class AskPermissionToCommitOutput(
+    stage: Int,
+    stageAttempt: Int,
+    partition: Int,
+    attemptNumber: Int)
 
 /**
  * Authority that decides whether tasks can commit output to HDFS. Uses a "first committer wins"
@@ -45,13 +49,15 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
   // Initialized by SparkEnv
   var coordinatorRef: Option[RpcEndpointRef] = None
 
-  private type StageId = Int
-  private type PartitionId = Int
-  private type TaskAttemptNumber = Int
-  private val NO_AUTHORIZED_COMMITTER: TaskAttemptNumber = -1
+  // Class used to identify a committer. The task ID for a committer is implicitly defined by
+  // the partition being processed, but the coordinator needs to keep track of both the stage
+  // attempt and the task attempt, because in some situations the same task may be running
+  // concurrently in two different attempts of the same stage.
+  private case class TaskIdentifier(stageAttempt: Int, taskAttempt: Int)
+
   private case class StageState(numPartitions: Int) {
-    val authorizedCommitters = Array.fill[TaskAttemptNumber](numPartitions)(NO_AUTHORIZED_COMMITTER)
-    val failures = mutable.Map[PartitionId, mutable.Set[TaskAttemptNumber]]()
+    val authorizedCommitters = Array.fill[TaskIdentifier](numPartitions)(null)
+    val failures = mutable.Map[Int, mutable.Set[TaskIdentifier]]()
   }
 
   /**
@@ -64,7 +70,7 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
    *
    * Access to this map should be guarded by synchronizing on the OutputCommitCoordinator instance.
    */
-  private val stageStates = mutable.Map[StageId, StageState]()
+  private val stageStates = mutable.Map[Int, StageState]()
 
   /**
    * Returns whether the OutputCommitCoordinator's internal data structures are all empty.
@@ -87,10 +93,11 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
    * @return true if this task is authorized to commit, false otherwise
    */
   def canCommit(
-      stage: StageId,
-      partition: PartitionId,
-      attemptNumber: TaskAttemptNumber): Boolean = {
-    val msg = AskPermissionToCommitOutput(stage, partition, attemptNumber)
+      stage: Int,
+      stageAttempt: Int,
+      partition: Int,
+      attemptNumber: Int): Boolean = {
+    val msg = AskPermissionToCommitOutput(stage, stageAttempt, partition, attemptNumber)
     coordinatorRef match {
       case Some(endpointRef) =>
         ThreadUtils.awaitResult(endpointRef.ask[Boolean](msg),
@@ -103,26 +110,35 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
   }
 
   /**
-   * Called by the DAGScheduler when a stage starts.
+   * Called by the DAGScheduler when a stage starts. Initializes the stage's state if it hasn't
+   * yet been initialized.
    *
    * @param stage the stage id.
    * @param maxPartitionId the maximum partition id that could appear in this stage's tasks (i.e.
    *                       the maximum possible value of `context.partitionId`).
    */
-  private[scheduler] def stageStart(stage: StageId, maxPartitionId: Int): Unit = synchronized {
-    stageStates(stage) = new StageState(maxPartitionId + 1)
+  private[scheduler] def stageStart(stage: Int, maxPartitionId: Int): Unit = synchronized {
+    stageStates.get(stage) match {
+      case Some(state) =>
+        require(state.authorizedCommitters.length == maxPartitionId + 1)
+        logInfo(s"Reusing state from previous attempt of stage $stage.")
+
+      case _ =>
+        stageStates(stage) = new StageState(maxPartitionId + 1)
+    }
   }
 
   // Called by DAGScheduler
-  private[scheduler] def stageEnd(stage: StageId): Unit = synchronized {
+  private[scheduler] def stageEnd(stage: Int): Unit = synchronized {
     stageStates.remove(stage)
   }
 
   // Called by DAGScheduler
   private[scheduler] def taskCompleted(
-      stage: StageId,
-      partition: PartitionId,
-      attemptNumber: TaskAttemptNumber,
+      stage: Int,
+      stageAttempt: Int,
+      partition: Int,
+      attemptNumber: Int,
       reason: TaskEndReason): Unit = synchronized {
     val stageState = stageStates.getOrElse(stage, {
       logDebug(s"Ignoring task completion for completed stage")
@@ -131,16 +147,17 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
     reason match {
       case Success =>
       // The task output has been committed successfully
-      case denied: TaskCommitDenied =>
-        logInfo(s"Task was denied committing, stage: $stage, partition: $partition, " +
-          s"attempt: $attemptNumber")
-      case otherReason =>
+      case _: TaskCommitDenied =>
+        logInfo(s"Task was denied committing, stage: $stage.$stageAttempt, " +
+          s"partition: $partition, attempt: $attemptNumber")
+      case _ =>
         // Mark the attempt as failed to blacklist from future commit protocol
-        stageState.failures.getOrElseUpdate(partition, mutable.Set()) += attemptNumber
-        if (stageState.authorizedCommitters(partition) == attemptNumber) {
+        val taskId = TaskIdentifier(stageAttempt, attemptNumber)
+        stageState.failures.getOrElseUpdate(partition, mutable.Set()) += taskId
+        if (stageState.authorizedCommitters(partition) == taskId) {
           logDebug(s"Authorized committer (attemptNumber=$attemptNumber, stage=$stage, " +
             s"partition=$partition) failed; clearing lock")
-          stageState.authorizedCommitters(partition) = NO_AUTHORIZED_COMMITTER
+          stageState.authorizedCommitters(partition) = null
         }
     }
   }
@@ -155,47 +172,41 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
 
   // Marked private[scheduler] instead of private so this can be mocked in tests
   private[scheduler] def handleAskPermissionToCommit(
-      stage: StageId,
-      partition: PartitionId,
-      attemptNumber: TaskAttemptNumber): Boolean = synchronized {
+      stage: Int,
+      stageAttempt: Int,
+      partition: Int,
+      attemptNumber: Int): Boolean = synchronized {
     stageStates.get(stage) match {
-      case Some(state) if attemptFailed(state, partition, attemptNumber) =>
-        logInfo(s"Denying attemptNumber=$attemptNumber to commit for stage=$stage," +
-          s" partition=$partition as task attempt $attemptNumber has already failed.")
+      case Some(state) if attemptFailed(state, stageAttempt, partition, attemptNumber) =>
+        logInfo(s"Commit denied for stage=$stage.$stageAttempt, partition=$partition: " +
+          s"task attempt $attemptNumber already marked as failed.")
         false
       case Some(state) =>
-        state.authorizedCommitters(partition) match {
-          case NO_AUTHORIZED_COMMITTER =>
-            logDebug(s"Authorizing attemptNumber=$attemptNumber to commit for stage=$stage, " +
-              s"partition=$partition")
-            state.authorizedCommitters(partition) = attemptNumber
-            true
-          case existingCommitter =>
-            // Coordinator should be idempotent when receiving AskPermissionToCommit.
-            if (existingCommitter == attemptNumber) {
-              logWarning(s"Authorizing duplicate request to commit for " +
-                s"attemptNumber=$attemptNumber to commit for stage=$stage," +
-                s" partition=$partition; existingCommitter = $existingCommitter." +
-                s" This can indicate dropped network traffic.")
-              true
-            } else {
-              logDebug(s"Denying attemptNumber=$attemptNumber to commit for stage=$stage, " +
-                s"partition=$partition; existingCommitter = $existingCommitter")
-              false
-            }
+        val existing = state.authorizedCommitters(partition)
+        if (existing == null) {
+          logDebug(s"Commit allowed for stage=$stage.$stageAttempt, partition=$partition, " +
+            s"task attempt $attemptNumber")
+          state.authorizedCommitters(partition) = TaskIdentifier(stageAttempt, attemptNumber)
+          true
+        } else {
+          logDebug(s"Commit denied for stage=$stage.$stageAttempt, partition=$partition: " +
+            s"already committed by $existing")
+          false
         }
       case None =>
-        logDebug(s"Stage $stage has completed, so not allowing" +
-          s" attempt number $attemptNumber of partition $partition to commit")
+        logDebug(s"Commit denied for stage=$stage.$stageAttempt, partition=$partition: " +
+          "stage already marked as completed.")
         false
     }
   }
 
   private def attemptFailed(
       stageState: StageState,
-      partition: PartitionId,
-      attempt: TaskAttemptNumber): Boolean = synchronized {
-    stageState.failures.get(partition).exists(_.contains(attempt))
+      stageAttempt: Int,
+      partition: Int,
+      attempt: Int): Boolean = synchronized {
+    val failInfo = TaskIdentifier(stageAttempt, attempt)
+    stageState.failures.get(partition).exists(_.contains(failInfo))
   }
 }
 
@@ -215,9 +226,10 @@ private[spark] object OutputCommitCoordinator {
     }
 
     override def receiveAndReply(context: RpcCallContext): PartialFunction[Any, Unit] = {
-      case AskPermissionToCommitOutput(stage, partition, attemptNumber) =>
+      case AskPermissionToCommitOutput(stage, stageAttempt, partition, attemptNumber) =>
         context.reply(
-          outputCommitCoordinator.handleAskPermissionToCommit(stage, partition, attemptNumber))
+          outputCommitCoordinator.handleAskPermissionToCommit(stage, stageAttempt, partition,
+            attemptNumber))
     }
   }
 }