[SPARK-18113] Use ask to replace askWithRetry in canCommit and make r…

…eceiver idempotent.

## What changes were proposed in this pull request?

Method canCommit sends AskPermissionToCommitOutput using askWithRetry. If timeout, it will send again. Thus AskPermissionToCommitOutput can be received multi times. Method canCommit should return the same value when called by the same attempt multi times.

In implementation before this fix, method handleAskPermissionToCommit just check if there is committer already registered, which is not enough. When worker retries AskPermissionToCommitOutput it will get CommitDeniedException, then the task will fail with reason TaskCommitDenied, which is not regarded as a task failure(SPARK-11178), so TaskScheduler will schedule this task infinitely.

In this fix, use `ask` to replace `askWithRetry` in `canCommit` and make receiver idempotent.

## How was this patch tested?

Added a new unit test to OutputCommitCoordinatorSuite.

Author: jinxing <[email protected]>

Closes apache#16503 from jinxing64/SPARK-18113.

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

@@ -22,6 +22,7 @@ import scala.collection.mutable
 import org.apache.spark._
 import org.apache.spark.internal.Logging
 import org.apache.spark.rpc.{RpcCallContext, RpcEndpoint, RpcEndpointRef, RpcEnv}
+import org.apache.spark.util.{RpcUtils, ThreadUtils}
 
 private sealed trait OutputCommitCoordinationMessage extends Serializable
 
@@ -88,7 +89,8 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
     val msg = AskPermissionToCommitOutput(stage, partition, attemptNumber)
     coordinatorRef match {
       case Some(endpointRef) =>
-        endpointRef.askWithRetry[Boolean](msg)
+        ThreadUtils.awaitResult(endpointRef.ask[Boolean](msg),
+          RpcUtils.askRpcTimeout(conf).duration)
       case None =>
         logError(
           "canCommit called after coordinator was stopped (is SparkEnv shutdown in progress)?")
@@ -165,9 +167,18 @@ private[spark] class OutputCommitCoordinator(conf: SparkConf, isDriver: Boolean)
             authorizedCommitters(partition) = attemptNumber
             true
           case existingCommitter =>
-            logDebug(s"Denying attemptNumber=$attemptNumber to commit for stage=$stage, " +
-              s"partition=$partition; existingCommitter = $existingCommitter")
-            false
+            // Coordinator should be idempotent when receiving AskPermissionToCommit.
+            if (existingCommitter == attemptNumber) {
+              logWarning(s"Authorizing duplicate request to commit for " +
+                s"attemptNumber=$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
+            }
         }
       case None =>
         logDebug(s"Stage $stage has completed, so not allowing attempt number $attemptNumber of" +

core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorSuite.scala

@@ -189,6 +189,12 @@ class OutputCommitCoordinatorSuite extends SparkFunSuite with BeforeAndAfter {
     assert(
       !outputCommitCoordinator.canCommit(stage, partition, nonAuthorizedCommitter + 3))
   }
+
+  test("Duplicate calls to canCommit from the authorized committer gets idempotent responses.") {
+    val rdd = sc.parallelize(Seq(1), 1)
+    sc.runJob(rdd, OutputCommitFunctions(tempDir.getAbsolutePath).callCanCommitMultipleTimes _,
+       0 until rdd.partitions.size)
+  }
 }
 
 /**
@@ -221,6 +227,16 @@ private case class OutputCommitFunctions(tempDirPath: String) {
       if (ctx.attemptNumber == 0) failingOutputCommitter else successfulOutputCommitter)
   }
 
+  // Receiver should be idempotent for AskPermissionToCommitOutput
+  def callCanCommitMultipleTimes(iter: Iterator[Int]): Unit = {
+    val ctx = TaskContext.get()
+    val canCommit1 = SparkEnv.get.outputCommitCoordinator
+      .canCommit(ctx.stageId(), ctx.partitionId(), ctx.attemptNumber())
+    val canCommit2 = SparkEnv.get.outputCommitCoordinator
+      .canCommit(ctx.stageId(), ctx.partitionId(), ctx.attemptNumber())
+    assert(canCommit1 && canCommit2)
+  }
+
   private def runCommitWithProvidedCommitter(
       ctx: TaskContext,
       iter: Iterator[Int],