attilapiros commented on a change in pull request #29014:
URL: https://github.com/apache/spark/pull/29014#discussion_r461567745



##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, false)
+    conf.set(config.UNREGISTER_OUTPUT_ON_HOST_ON_FETCH_FAILURE, true)
+    createWorkers(2)
+    sc = createSparkContext(conf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val executorToDecom = executorIdToWorkerInfo.keysIterator.next
+
+    // The task code below cannot call executorIdToWorkerInfo, so we need to 
pre-compute
+    // the worker to decom to force it to be serialized into the task.
+    val workerToDecom = executorIdToWorkerInfo(executorToDecom)
+
+    // The setup of this job is similar to the one above: 2 stage job with 
first stage having
+    // long and short tasks. Except that we want the shuffle output to be 
regenerated on a
+    // fetch failure instead of an executor lost. Since it is hard to "trigger 
a fetch failure",
+    // we manually raise the FetchFailed exception when the 2nd stage's task 
runs and require that
+    // fetch failure to trigger a recomputation.
+    logInfo(s"Will try to decommission the task running on executor 
$executorToDecom")
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+        val taskInfo = taskEnd.taskInfo
+        if (taskInfo.executorId == executorToDecom && taskInfo.attemptNumber 
== 0 &&
+          taskEnd.stageAttemptId == 0) {
+          decommissionWorkerOnMaster(workerToDecom,
+            "decommission worker after task on it is done")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((_, _) 
=> {
+        val executorId = SparkEnv.get.executorId
+        val sleepTimeSeconds = if (executorId == executorToDecom) 10 else 1
+        Thread.sleep(sleepTimeSeconds * 1000L)
+        List(1).iterator
+      }, preservesPartitioning = true)
+        .repartition(1).mapPartitions(iter => {
+        val context = TaskContext.get()
+        if (context.attemptNumber == 0 && context.stageAttemptNumber() == 0) {
+          // MapIndex is explicitly -1 to force the entire host to be 
decommissioned
+          // However, this will cause both the tasks in the preceding stage 
since the host here is
+          // "localhost" (shortcoming of this single-machine unit test in that 
all the workers
+          // are actually on the same host)
+          throw new FetchFailedException(BlockManagerId(executorToDecom,
+            workerToDecom.host, workerToDecom.port), 0, 0, -1, 0, "Forcing 
fetch failure")
+        }
+        val sumVal: List[Int] = List(iter.sum)
+        sumVal.iterator
+      }, preservesPartitioning = true)
+        .sum()
+      assert(jobResult === 2)
+    }
+    // 6 tasks: 2 from first stage, 2 rerun again from first stage, 2nd stage 
attempt 1 and 2.
+    val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+    assert(tasksSeen.size === 6, s"Expected 6 tasks but got $tasksSeen")
+  }
+
+  private abstract class RootStageAwareListener extends SparkListener {
+    private var rootStageId: Option[Int] = None
+    private val tasksFinished = new ConcurrentLinkedQueue[String]()
+    private val jobDone = new AtomicBoolean(false)
+    protected val rootTasksStarted = new ConcurrentLinkedQueue[TaskInfo]()
+    protected val rootTasksEnded = new ConcurrentLinkedQueue[TaskInfo]()
+
+    protected def isRootStageId(stageId: Int): Boolean =
+      (rootStageId.isDefined && rootStageId.get == stageId)
+
+    override def onStageSubmitted(stageSubmitted: 
SparkListenerStageSubmitted): Unit = {
+      if (stageSubmitted.stageInfo.parentIds.isEmpty && rootStageId.isEmpty) {
+        rootStageId = Some(stageSubmitted.stageInfo.stageId)
+      }
+    }
+
+    override def onJobEnd(jobEnd: SparkListenerJobEnd): Unit = {
+      jobEnd.jobResult match {
+        case JobSucceeded => jobDone.set(true)
+      }
+    }
+
+    protected def handleRootTaskEnd(end: SparkListenerTaskEnd) = {}
+
+    protected def handleRootTaskStart(start: SparkListenerTaskStart) = {}
+
+    protected def validate(): Unit = {}
+
+    override def onTaskStart(taskStart: SparkListenerTaskStart): Unit = {
+      if (isRootStageId(taskStart.stageId)) {
+        rootTasksStarted.add(taskStart.taskInfo)
+        handleRootTaskStart(taskStart)
+      }
+    }
+
+    override def onTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+      val taskSignature = s"${taskEnd.stageId}:${taskEnd.stageAttemptId}:" +
+        s"${taskEnd.taskInfo.index}:${taskEnd.taskInfo.attemptNumber}"
+      logInfo(s"Task End $taskSignature")
+      tasksFinished.add(taskSignature)
+      if (isRootStageId(taskEnd.stageId)) {
+        rootTasksEnded.add(taskEnd.taskInfo)
+        handleRootTaskEnd(taskEnd)
+      }
+    }
+
+    def getTasksFinishedEnsuringCleanJobRun(): Seq[String] = {
+      assert(jobDone.get(), "Job isn't successfully done yet")
+      validate()
+      tasksFinished.asScala.toSeq
+    }
+  }
+
+  private def getExecutorToWorkerAssignments: Map[String, WorkerInfo] = {
+    val executorIdToWorkerInfo = mutable.HashMap[String, WorkerInfo]()
+    master.workers.foreach { wi =>
+      assert(wi.executors.size <= 1, "There should be at most one executor per 
worker")
+      // Cast the executorId to string since the TaskInfo.executorId is a 
string
+      wi.executors.values.foreach { e =>
+        val executorIdString = e.id.toString
+        val oldWorkerInfo = executorIdToWorkerInfo.put(executorIdString, wi)
+        assert(oldWorkerInfo.isEmpty,
+          s"Executor $executorIdString already present on another worker 
${oldWorkerInfo}")
+      }
+    }
+    executorIdToWorkerInfo.toMap
+  }
+
+  private def appConf: SparkConf = {
+    new SparkConf()
+      .setMaster(masterRpcEnv.address.toSparkURL)
+      .setAppName("test")
+      .set(config.EXECUTOR_CORES.key, "1")
+      .set(config.EXECUTOR_MEMORY.key, "1024m") // one exec per worker
+  }
+
+  private def makeMaster(): Master = {
+    val master = new Master(masterRpcEnv, masterRpcEnv.address, 0, 
securityManager, conf)
+    masterRpcEnv.setupEndpoint(Master.ENDPOINT_NAME, master)
+    master
+  }
+
+  private def createWorkers(numWorkers: Int, cores: Int = 1, memory: Int = 
1024): Unit = {
+    val workerRpcEnvs = (0 until numWorkers).map { i =>
+      RpcEnv.create(Worker.SYSTEM_NAME + i, "localhost", 0, conf, 
securityManager)
+    }
+    workers.clear()
+    val rpcAddressToRpcEnv: mutable.HashMap[RpcAddress, RpcEnv] = 
mutable.HashMap.empty
+    workerRpcEnvs.foreach { rpcEnv =>
+      val workDir = Utils.createTempDir(namePrefix = 
this.getClass.getSimpleName()).toString
+      val worker = new Worker(rpcEnv, 0, cores, memory, 
Array(masterRpcEnv.address),
+        Worker.ENDPOINT_NAME, workDir, conf, securityManager)
+      rpcEnv.setupEndpoint(Worker.ENDPOINT_NAME, worker)
+      workers.append(worker)
+      val oldRpcEnv = rpcAddressToRpcEnv.put(rpcEnv.address, rpcEnv)
+      logInfo(s"Created a worker at ${rpcEnv.address} with workdir $workDir")
+      assert(oldRpcEnv.isEmpty, s"Detected duplicate rpcEnv ${oldRpcEnv} for 
${rpcEnv.address}")
+    }
+    workerIdToRpcEnvs.clear()
+    // Wait until all workers register with master successfully
+    eventually(timeout(1.minute), interval(1.seconds)) {
+      val workersOnMaster = getMasterState.workers
+      val numWorkersCurrently = workersOnMaster.length
+      logInfo(s"Waiting for $numWorkers workers to come up: So far 
$numWorkersCurrently")
+      assert(numWorkersCurrently === numWorkers)
+      workersOnMaster.foreach { workerInfo =>
+        val rpcAddress = RpcAddress(workerInfo.host, workerInfo.port)
+        val rpcEnv = rpcAddressToRpcEnv(rpcAddress)
+        assert(rpcEnv != null, s"Cannot find the worker for $rpcAddress")
+        val oldRpcEnv = workerIdToRpcEnvs.put(workerInfo.id, rpcEnv)
+        assert(oldRpcEnv.isEmpty, s"Detected duplicate rpcEnv ${oldRpcEnv} for 
worker " +
+          s"${workerInfo.id}")
+      }
+    }
+    logInfo(s"Created ${workers.size} workers")
+  }
+
+  private def getMasterState: MasterStateResponse = {
+    master.self.askSync[MasterStateResponse](RequestMasterState)
+  }
+
+  private def getApplications(): Seq[ApplicationInfo] = {
+    getMasterState.activeApps
+  }
+
+  def decommissionWorkerOnMaster(workerInfo: WorkerInfo, reason: String): Unit 
= {
+    logInfo(s"Trying to decommission worker ${workerInfo.id} for reason 
`$reason`")
+    master.self.send(WorkerDecommission(workerInfo.id, workerInfo.endpoint))
+  }
+
+  def killWorkerAfterTimeout(workerInfo: WorkerInfo, secondsToWait: Integer): 
Unit = {
+    val env = workerIdToRpcEnvs(workerInfo.id)
+    Thread.sleep(secondsToWait * 1000L)
+    env.shutdown()
+    env.awaitTermination()
+  }
+
+  def createSparkContext(conf: SparkConf): SparkContext = {
+    sc = new SparkContext(conf)
+    val appId = sc.applicationId
+    eventually(timeout(1.minute), interval(1.seconds)) {
+      val apps = getApplications()
+      assert(apps.size === 1)
+      assert(apps.head.id === appId)
+      assert(apps.head.getExecutorLimit === Int.MaxValue)
+    }
+    sc
+  }
+
+  private class ExternalShuffleServiceHolder(conf: SparkConf) {
+    private val transportConf = SparkTransportConf.fromSparkConf(conf,
+      "shuffle", numUsableCores = 2)
+    private var rpcHandler = new ExternalBlockHandler(transportConf, null)
+    private var transportContext = new TransportContext(transportConf, 
rpcHandler)
+    private var server = transportContext.createServer()

Review comment:
       Nit: These can be `vals` and all the resets to null can be removed as it 
used only once and not reused:
   
   
https://github.com/apache/spark/blob/806630a19437b370a295010645bf949ee0541aeb/core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala#L134
   

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, false)
+    conf.set(config.UNREGISTER_OUTPUT_ON_HOST_ON_FETCH_FAILURE, true)
+    createWorkers(2)
+    sc = createSparkContext(conf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val executorToDecom = executorIdToWorkerInfo.keysIterator.next
+
+    // The task code below cannot call executorIdToWorkerInfo, so we need to 
pre-compute
+    // the worker to decom to force it to be serialized into the task.
+    val workerToDecom = executorIdToWorkerInfo(executorToDecom)
+
+    // The setup of this job is similar to the one above: 2 stage job with 
first stage having
+    // long and short tasks. Except that we want the shuffle output to be 
regenerated on a
+    // fetch failure instead of an executor lost. Since it is hard to "trigger 
a fetch failure",
+    // we manually raise the FetchFailed exception when the 2nd stage's task 
runs and require that
+    // fetch failure to trigger a recomputation.
+    logInfo(s"Will try to decommission the task running on executor 
$executorToDecom")
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+        val taskInfo = taskEnd.taskInfo
+        if (taskInfo.executorId == executorToDecom && taskInfo.attemptNumber 
== 0 &&
+          taskEnd.stageAttemptId == 0) {
+          decommissionWorkerOnMaster(workerToDecom,
+            "decommission worker after task on it is done")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((_, _) 
=> {
+        val executorId = SparkEnv.get.executorId
+        val sleepTimeSeconds = if (executorId == executorToDecom) 10 else 1
+        Thread.sleep(sleepTimeSeconds * 1000L)
+        List(1).iterator
+      }, preservesPartitioning = true)
+        .repartition(1).mapPartitions(iter => {
+        val context = TaskContext.get()
+        if (context.attemptNumber == 0 && context.stageAttemptNumber() == 0) {
+          // MapIndex is explicitly -1 to force the entire host to be 
decommissioned
+          // However, this will cause both the tasks in the preceding stage 
since the host here is
+          // "localhost" (shortcoming of this single-machine unit test in that 
all the workers
+          // are actually on the same host)
+          throw new FetchFailedException(BlockManagerId(executorToDecom,
+            workerToDecom.host, workerToDecom.port), 0, 0, -1, 0, "Forcing 
fetch failure")
+        }
+        val sumVal: List[Int] = List(iter.sum)
+        sumVal.iterator
+      }, preservesPartitioning = true)
+        .sum()
+      assert(jobResult === 2)
+    }
+    // 6 tasks: 2 from first stage, 2 rerun again from first stage, 2nd stage 
attempt 1 and 2.
+    val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+    assert(tasksSeen.size === 6, s"Expected 6 tasks but got $tasksSeen")
+  }
+
+  private abstract class RootStageAwareListener extends SparkListener {
+    private var rootStageId: Option[Int] = None
+    private val tasksFinished = new ConcurrentLinkedQueue[String]()
+    private val jobDone = new AtomicBoolean(false)
+    protected val rootTasksStarted = new ConcurrentLinkedQueue[TaskInfo]()
+    protected val rootTasksEnded = new ConcurrentLinkedQueue[TaskInfo]()
+
+    protected def isRootStageId(stageId: Int): Boolean =
+      (rootStageId.isDefined && rootStageId.get == stageId)
+
+    override def onStageSubmitted(stageSubmitted: 
SparkListenerStageSubmitted): Unit = {
+      if (stageSubmitted.stageInfo.parentIds.isEmpty && rootStageId.isEmpty) {
+        rootStageId = Some(stageSubmitted.stageInfo.stageId)
+      }
+    }
+
+    override def onJobEnd(jobEnd: SparkListenerJobEnd): Unit = {
+      jobEnd.jobResult match {
+        case JobSucceeded => jobDone.set(true)
+      }
+    }
+
+    protected def handleRootTaskEnd(end: SparkListenerTaskEnd) = {}
+
+    protected def handleRootTaskStart(start: SparkListenerTaskStart) = {}
+
+    protected def validate(): Unit = {}
+
+    override def onTaskStart(taskStart: SparkListenerTaskStart): Unit = {
+      if (isRootStageId(taskStart.stageId)) {
+        rootTasksStarted.add(taskStart.taskInfo)
+        handleRootTaskStart(taskStart)
+      }
+    }
+
+    override def onTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+      val taskSignature = s"${taskEnd.stageId}:${taskEnd.stageAttemptId}:" +
+        s"${taskEnd.taskInfo.index}:${taskEnd.taskInfo.attemptNumber}"
+      logInfo(s"Task End $taskSignature")
+      tasksFinished.add(taskSignature)
+      if (isRootStageId(taskEnd.stageId)) {
+        rootTasksEnded.add(taskEnd.taskInfo)
+        handleRootTaskEnd(taskEnd)
+      }
+    }
+
+    def getTasksFinishedEnsuringCleanJobRun(): Seq[String] = {
+      assert(jobDone.get(), "Job isn't successfully done yet")
+      validate()
+      tasksFinished.asScala.toSeq
+    }
+  }
+
+  private def getExecutorToWorkerAssignments: Map[String, WorkerInfo] = {
+    val executorIdToWorkerInfo = mutable.HashMap[String, WorkerInfo]()
+    master.workers.foreach { wi =>
+      assert(wi.executors.size <= 1, "There should be at most one executor per 
worker")
+      // Cast the executorId to string since the TaskInfo.executorId is a 
string
+      wi.executors.values.foreach { e =>
+        val executorIdString = e.id.toString
+        val oldWorkerInfo = executorIdToWorkerInfo.put(executorIdString, wi)
+        assert(oldWorkerInfo.isEmpty,
+          s"Executor $executorIdString already present on another worker 
${oldWorkerInfo}")
+      }
+    }
+    executorIdToWorkerInfo.toMap
+  }
+
+  private def appConf: SparkConf = {
+    new SparkConf()
+      .setMaster(masterRpcEnv.address.toSparkURL)
+      .setAppName("test")
+      .set(config.EXECUTOR_CORES.key, "1")
+      .set(config.EXECUTOR_MEMORY.key, "1024m") // one exec per worker
+  }
+
+  private def makeMaster(): Master = {
+    val master = new Master(masterRpcEnv, masterRpcEnv.address, 0, 
securityManager, conf)
+    masterRpcEnv.setupEndpoint(Master.ENDPOINT_NAME, master)
+    master
+  }
+
+  private def createWorkers(numWorkers: Int, cores: Int = 1, memory: Int = 
1024): Unit = {
+    val workerRpcEnvs = (0 until numWorkers).map { i =>
+      RpcEnv.create(Worker.SYSTEM_NAME + i, "localhost", 0, conf, 
securityManager)
+    }
+    workers.clear()
+    val rpcAddressToRpcEnv: mutable.HashMap[RpcAddress, RpcEnv] = 
mutable.HashMap.empty
+    workerRpcEnvs.foreach { rpcEnv =>
+      val workDir = Utils.createTempDir(namePrefix = 
this.getClass.getSimpleName()).toString
+      val worker = new Worker(rpcEnv, 0, cores, memory, 
Array(masterRpcEnv.address),
+        Worker.ENDPOINT_NAME, workDir, conf, securityManager)
+      rpcEnv.setupEndpoint(Worker.ENDPOINT_NAME, worker)
+      workers.append(worker)
+      val oldRpcEnv = rpcAddressToRpcEnv.put(rpcEnv.address, rpcEnv)
+      logInfo(s"Created a worker at ${rpcEnv.address} with workdir $workDir")
+      assert(oldRpcEnv.isEmpty, s"Detected duplicate rpcEnv ${oldRpcEnv} for 
${rpcEnv.address}")
+    }
+    workerIdToRpcEnvs.clear()
+    // Wait until all workers register with master successfully
+    eventually(timeout(1.minute), interval(1.seconds)) {
+      val workersOnMaster = getMasterState.workers
+      val numWorkersCurrently = workersOnMaster.length
+      logInfo(s"Waiting for $numWorkers workers to come up: So far 
$numWorkersCurrently")
+      assert(numWorkersCurrently === numWorkers)
+      workersOnMaster.foreach { workerInfo =>
+        val rpcAddress = RpcAddress(workerInfo.host, workerInfo.port)
+        val rpcEnv = rpcAddressToRpcEnv(rpcAddress)
+        assert(rpcEnv != null, s"Cannot find the worker for $rpcAddress")
+        val oldRpcEnv = workerIdToRpcEnvs.put(workerInfo.id, rpcEnv)
+        assert(oldRpcEnv.isEmpty, s"Detected duplicate rpcEnv ${oldRpcEnv} for 
worker " +
+          s"${workerInfo.id}")
+      }
+    }
+    logInfo(s"Created ${workers.size} workers")
+  }
+
+  private def getMasterState: MasterStateResponse = {
+    master.self.askSync[MasterStateResponse](RequestMasterState)
+  }
+
+  private def getApplications(): Seq[ApplicationInfo] = {
+    getMasterState.activeApps
+  }
+
+  def decommissionWorkerOnMaster(workerInfo: WorkerInfo, reason: String): Unit 
= {
+    logInfo(s"Trying to decommission worker ${workerInfo.id} for reason 
`$reason`")
+    master.self.send(WorkerDecommission(workerInfo.id, workerInfo.endpoint))
+  }
+
+  def killWorkerAfterTimeout(workerInfo: WorkerInfo, secondsToWait: Integer): 
Unit = {
+    val env = workerIdToRpcEnvs(workerInfo.id)
+    Thread.sleep(secondsToWait * 1000L)
+    env.shutdown()
+    env.awaitTermination()
+  }
+
+  def createSparkContext(conf: SparkConf): SparkContext = {
+    sc = new SparkContext(conf)
+    val appId = sc.applicationId
+    eventually(timeout(1.minute), interval(1.seconds)) {
+      val apps = getApplications()
+      assert(apps.size === 1)
+      assert(apps.head.id === appId)
+      assert(apps.head.getExecutorLimit === Int.MaxValue)
+    }
+    sc
+  }
+
+  private class ExternalShuffleServiceHolder(conf: SparkConf) {
+    private val transportConf = SparkTransportConf.fromSparkConf(conf,
+      "shuffle", numUsableCores = 2)
+    private var rpcHandler = new ExternalBlockHandler(transportConf, null)
+    private var transportContext = new TransportContext(transportConf, 
rpcHandler)
+    private var server = transportContext.createServer()

Review comment:
       Nit: These can be `vals` and all the resets to null can be removed as 
`ExternalShuffleServiceHolder` used only once and not reused:
   
   
https://github.com/apache/spark/blob/806630a19437b370a295010645bf949ee0541aeb/core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala#L134
   

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)

Review comment:
       The `conf` is global and this way `config.TASK_MAX_FAILURES` will be set 
to 2 on other test methods depending on this test was before or after. At least 
let's set this at the declaration to avoid this side effect.  

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, false)
+    conf.set(config.UNREGISTER_OUTPUT_ON_HOST_ON_FETCH_FAILURE, true)
+    createWorkers(2)
+    sc = createSparkContext(conf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val executorToDecom = executorIdToWorkerInfo.keysIterator.next
+
+    // The task code below cannot call executorIdToWorkerInfo, so we need to 
pre-compute
+    // the worker to decom to force it to be serialized into the task.
+    val workerToDecom = executorIdToWorkerInfo(executorToDecom)
+
+    // The setup of this job is similar to the one above: 2 stage job with 
first stage having
+    // long and short tasks. Except that we want the shuffle output to be 
regenerated on a
+    // fetch failure instead of an executor lost. Since it is hard to "trigger 
a fetch failure",
+    // we manually raise the FetchFailed exception when the 2nd stage's task 
runs and require that
+    // fetch failure to trigger a recomputation.
+    logInfo(s"Will try to decommission the task running on executor 
$executorToDecom")
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+        val taskInfo = taskEnd.taskInfo
+        if (taskInfo.executorId == executorToDecom && taskInfo.attemptNumber 
== 0 &&
+          taskEnd.stageAttemptId == 0) {
+          decommissionWorkerOnMaster(workerToDecom,
+            "decommission worker after task on it is done")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((_, _) 
=> {
+        val executorId = SparkEnv.get.executorId
+        val sleepTimeSeconds = if (executorId == executorToDecom) 10 else 1
+        Thread.sleep(sleepTimeSeconds * 1000L)
+        List(1).iterator
+      }, preservesPartitioning = true)
+        .repartition(1).mapPartitions(iter => {
+        val context = TaskContext.get()
+        if (context.attemptNumber == 0 && context.stageAttemptNumber() == 0) {
+          // MapIndex is explicitly -1 to force the entire host to be 
decommissioned
+          // However, this will cause both the tasks in the preceding stage 
since the host here is
+          // "localhost" (shortcoming of this single-machine unit test in that 
all the workers
+          // are actually on the same host)
+          throw new FetchFailedException(BlockManagerId(executorToDecom,
+            workerToDecom.host, workerToDecom.port), 0, 0, -1, 0, "Forcing 
fetch failure")
+        }
+        val sumVal: List[Int] = List(iter.sum)
+        sumVal.iterator
+      }, preservesPartitioning = true)
+        .sum()
+      assert(jobResult === 2)
+    }
+    // 6 tasks: 2 from first stage, 2 rerun again from first stage, 2nd stage 
attempt 1 and 2.
+    val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+    assert(tasksSeen.size === 6, s"Expected 6 tasks but got $tasksSeen")
+  }
+
+  private abstract class RootStageAwareListener extends SparkListener {
+    private var rootStageId: Option[Int] = None
+    private val tasksFinished = new ConcurrentLinkedQueue[String]()
+    private val jobDone = new AtomicBoolean(false)
+    protected val rootTasksStarted = new ConcurrentLinkedQueue[TaskInfo]()
+    protected val rootTasksEnded = new ConcurrentLinkedQueue[TaskInfo]()
+
+    protected def isRootStageId(stageId: Int): Boolean =
+      (rootStageId.isDefined && rootStageId.get == stageId)
+
+    override def onStageSubmitted(stageSubmitted: 
SparkListenerStageSubmitted): Unit = {
+      if (stageSubmitted.stageInfo.parentIds.isEmpty && rootStageId.isEmpty) {
+        rootStageId = Some(stageSubmitted.stageInfo.stageId)
+      }
+    }
+
+    override def onJobEnd(jobEnd: SparkListenerJobEnd): Unit = {
+      jobEnd.jobResult match {
+        case JobSucceeded => jobDone.set(true)
+      }
+    }
+
+    protected def handleRootTaskEnd(end: SparkListenerTaskEnd) = {}
+
+    protected def handleRootTaskStart(start: SparkListenerTaskStart) = {}
+
+    protected def validate(): Unit = {}
+
+    override def onTaskStart(taskStart: SparkListenerTaskStart): Unit = {
+      if (isRootStageId(taskStart.stageId)) {
+        rootTasksStarted.add(taskStart.taskInfo)
+        handleRootTaskStart(taskStart)
+      }
+    }
+
+    override def onTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+      val taskSignature = s"${taskEnd.stageId}:${taskEnd.stageAttemptId}:" +
+        s"${taskEnd.taskInfo.index}:${taskEnd.taskInfo.attemptNumber}"
+      logInfo(s"Task End $taskSignature")
+      tasksFinished.add(taskSignature)
+      if (isRootStageId(taskEnd.stageId)) {
+        rootTasksEnded.add(taskEnd.taskInfo)
+        handleRootTaskEnd(taskEnd)
+      }
+    }
+
+    def getTasksFinishedEnsuringCleanJobRun(): Seq[String] = {

Review comment:
       I believe now the validation can be part of the tests and not the 
listener.
   I would change `rootTasksStarted` and `rootTasksEnded` from `protected` to 
package private, remove the `validate` method in each tests I would move the 
validation body after the `getTasksFinishedEnsuringCleanJobRun` call. Finally I 
would rename this to `getTasksFinished` (aka. single responsibility principle). 
   

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf

Review comment:
       Variable shadowing. I would use a different name.

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)

Review comment:
       In `conf` you set the  `TASK_MAX_FAILURES` to 2 but it seems to me that 
conf is not used after this but the `appConf`.
   
   When you fixed this please double check it really has effect to the 
execution. 

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, false)
+    conf.set(config.UNREGISTER_OUTPUT_ON_HOST_ON_FETCH_FAILURE, true)
+    createWorkers(2)
+    sc = createSparkContext(conf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val executorToDecom = executorIdToWorkerInfo.keysIterator.next
+
+    // The task code below cannot call executorIdToWorkerInfo, so we need to 
pre-compute
+    // the worker to decom to force it to be serialized into the task.
+    val workerToDecom = executorIdToWorkerInfo(executorToDecom)
+
+    // The setup of this job is similar to the one above: 2 stage job with 
first stage having
+    // long and short tasks. Except that we want the shuffle output to be 
regenerated on a
+    // fetch failure instead of an executor lost. Since it is hard to "trigger 
a fetch failure",
+    // we manually raise the FetchFailed exception when the 2nd stage's task 
runs and require that
+    // fetch failure to trigger a recomputation.
+    logInfo(s"Will try to decommission the task running on executor 
$executorToDecom")
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+        val taskInfo = taskEnd.taskInfo
+        if (taskInfo.executorId == executorToDecom && taskInfo.attemptNumber 
== 0 &&
+          taskEnd.stageAttemptId == 0) {
+          decommissionWorkerOnMaster(workerToDecom,
+            "decommission worker after task on it is done")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((_, _) 
=> {
+        val executorId = SparkEnv.get.executorId
+        val sleepTimeSeconds = if (executorId == executorToDecom) 10 else 1
+        Thread.sleep(sleepTimeSeconds * 1000L)
+        List(1).iterator
+      }, preservesPartitioning = true)
+        .repartition(1).mapPartitions(iter => {
+        val context = TaskContext.get()
+        if (context.attemptNumber == 0 && context.stageAttemptNumber() == 0) {
+          // MapIndex is explicitly -1 to force the entire host to be 
decommissioned
+          // However, this will cause both the tasks in the preceding stage 
since the host here is
+          // "localhost" (shortcoming of this single-machine unit test in that 
all the workers
+          // are actually on the same host)
+          throw new FetchFailedException(BlockManagerId(executorToDecom,
+            workerToDecom.host, workerToDecom.port), 0, 0, -1, 0, "Forcing 
fetch failure")
+        }
+        val sumVal: List[Int] = List(iter.sum)
+        sumVal.iterator
+      }, preservesPartitioning = true)
+        .sum()
+      assert(jobResult === 2)
+    }
+    // 6 tasks: 2 from first stage, 2 rerun again from first stage, 2nd stage 
attempt 1 and 2.
+    val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+    assert(tasksSeen.size === 6, s"Expected 6 tasks but got $tasksSeen")
+  }
+
+  private abstract class RootStageAwareListener extends SparkListener {
+    private var rootStageId: Option[Int] = None
+    private val tasksFinished = new ConcurrentLinkedQueue[String]()
+    private val jobDone = new AtomicBoolean(false)
+    protected val rootTasksStarted = new ConcurrentLinkedQueue[TaskInfo]()
+    protected val rootTasksEnded = new ConcurrentLinkedQueue[TaskInfo]()
+
+    protected def isRootStageId(stageId: Int): Boolean =
+      (rootStageId.isDefined && rootStageId.get == stageId)
+
+    override def onStageSubmitted(stageSubmitted: 
SparkListenerStageSubmitted): Unit = {
+      if (stageSubmitted.stageInfo.parentIds.isEmpty && rootStageId.isEmpty) {
+        rootStageId = Some(stageSubmitted.stageInfo.stageId)
+      }
+    }
+
+    override def onJobEnd(jobEnd: SparkListenerJobEnd): Unit = {
+      jobEnd.jobResult match {
+        case JobSucceeded => jobDone.set(true)
+      }
+    }
+
+    protected def handleRootTaskEnd(end: SparkListenerTaskEnd) = {}
+
+    protected def handleRootTaskStart(start: SparkListenerTaskStart) = {}
+
+    protected def validate(): Unit = {}
+
+    override def onTaskStart(taskStart: SparkListenerTaskStart): Unit = {
+      if (isRootStageId(taskStart.stageId)) {
+        rootTasksStarted.add(taskStart.taskInfo)
+        handleRootTaskStart(taskStart)
+      }
+    }
+
+    override def onTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+      val taskSignature = s"${taskEnd.stageId}:${taskEnd.stageAttemptId}:" +
+        s"${taskEnd.taskInfo.index}:${taskEnd.taskInfo.attemptNumber}"
+      logInfo(s"Task End $taskSignature")
+      tasksFinished.add(taskSignature)
+      if (isRootStageId(taskEnd.stageId)) {
+        rootTasksEnded.add(taskEnd.taskInfo)
+        handleRootTaskEnd(taskEnd)
+      }
+    }
+
+    def getTasksFinishedEnsuringCleanJobRun(): Seq[String] = {
+      assert(jobDone.get(), "Job isn't successfully done yet")
+      validate()
+      tasksFinished.asScala.toSeq
+    }
+  }
+
+  private def getExecutorToWorkerAssignments: Map[String, WorkerInfo] = {
+    val executorIdToWorkerInfo = mutable.HashMap[String, WorkerInfo]()
+    master.workers.foreach { wi =>
+      assert(wi.executors.size <= 1, "There should be at most one executor per 
worker")
+      // Cast the executorId to string since the TaskInfo.executorId is a 
string
+      wi.executors.values.foreach { e =>
+        val executorIdString = e.id.toString
+        val oldWorkerInfo = executorIdToWorkerInfo.put(executorIdString, wi)
+        assert(oldWorkerInfo.isEmpty,
+          s"Executor $executorIdString already present on another worker 
${oldWorkerInfo}")
+      }
+    }
+    executorIdToWorkerInfo.toMap
+  }
+
+  private def appConf: SparkConf = {
+    new SparkConf()
+      .setMaster(masterRpcEnv.address.toSparkURL)
+      .setAppName("test")
+      .set(config.EXECUTOR_CORES.key, "1")
+      .set(config.EXECUTOR_MEMORY.key, "1024m") // one exec per worker

Review comment:
       Both set to the defaults.

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")
+    } finally {
+      ss.close()
+    }
+  }
+
+  test("decommission workers ensure that fetch failures lead to rerun") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, false)
+    conf.set(config.UNREGISTER_OUTPUT_ON_HOST_ON_FETCH_FAILURE, true)
+    createWorkers(2)
+    sc = createSparkContext(conf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val executorToDecom = executorIdToWorkerInfo.keysIterator.next
+
+    // The task code below cannot call executorIdToWorkerInfo, so we need to 
pre-compute
+    // the worker to decom to force it to be serialized into the task.
+    val workerToDecom = executorIdToWorkerInfo(executorToDecom)
+
+    // The setup of this job is similar to the one above: 2 stage job with 
first stage having
+    // long and short tasks. Except that we want the shuffle output to be 
regenerated on a
+    // fetch failure instead of an executor lost. Since it is hard to "trigger 
a fetch failure",
+    // we manually raise the FetchFailed exception when the 2nd stage's task 
runs and require that
+    // fetch failure to trigger a recomputation.
+    logInfo(s"Will try to decommission the task running on executor 
$executorToDecom")
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+        val taskInfo = taskEnd.taskInfo
+        if (taskInfo.executorId == executorToDecom && taskInfo.attemptNumber 
== 0 &&
+          taskEnd.stageAttemptId == 0) {
+          decommissionWorkerOnMaster(workerToDecom,
+            "decommission worker after task on it is done")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((_, _) 
=> {
+        val executorId = SparkEnv.get.executorId
+        val sleepTimeSeconds = if (executorId == executorToDecom) 10 else 1
+        Thread.sleep(sleepTimeSeconds * 1000L)
+        List(1).iterator
+      }, preservesPartitioning = true)
+        .repartition(1).mapPartitions(iter => {
+        val context = TaskContext.get()
+        if (context.attemptNumber == 0 && context.stageAttemptNumber() == 0) {
+          // MapIndex is explicitly -1 to force the entire host to be 
decommissioned
+          // However, this will cause both the tasks in the preceding stage 
since the host here is
+          // "localhost" (shortcoming of this single-machine unit test in that 
all the workers
+          // are actually on the same host)
+          throw new FetchFailedException(BlockManagerId(executorToDecom,
+            workerToDecom.host, workerToDecom.port), 0, 0, -1, 0, "Forcing 
fetch failure")
+        }
+        val sumVal: List[Int] = List(iter.sum)
+        sumVal.iterator
+      }, preservesPartitioning = true)
+        .sum()
+      assert(jobResult === 2)
+    }
+    // 6 tasks: 2 from first stage, 2 rerun again from first stage, 2nd stage 
attempt 1 and 2.
+    val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+    assert(tasksSeen.size === 6, s"Expected 6 tasks but got $tasksSeen")
+  }
+
+  private abstract class RootStageAwareListener extends SparkListener {
+    private var rootStageId: Option[Int] = None
+    private val tasksFinished = new ConcurrentLinkedQueue[String]()
+    private val jobDone = new AtomicBoolean(false)
+    protected val rootTasksStarted = new ConcurrentLinkedQueue[TaskInfo]()
+    protected val rootTasksEnded = new ConcurrentLinkedQueue[TaskInfo]()
+
+    protected def isRootStageId(stageId: Int): Boolean =
+      (rootStageId.isDefined && rootStageId.get == stageId)
+
+    override def onStageSubmitted(stageSubmitted: 
SparkListenerStageSubmitted): Unit = {
+      if (stageSubmitted.stageInfo.parentIds.isEmpty && rootStageId.isEmpty) {
+        rootStageId = Some(stageSubmitted.stageInfo.stageId)
+      }
+    }
+
+    override def onJobEnd(jobEnd: SparkListenerJobEnd): Unit = {
+      jobEnd.jobResult match {
+        case JobSucceeded => jobDone.set(true)
+      }
+    }
+
+    protected def handleRootTaskEnd(end: SparkListenerTaskEnd) = {}
+
+    protected def handleRootTaskStart(start: SparkListenerTaskStart) = {}
+
+    protected def validate(): Unit = {}
+
+    override def onTaskStart(taskStart: SparkListenerTaskStart): Unit = {
+      if (isRootStageId(taskStart.stageId)) {
+        rootTasksStarted.add(taskStart.taskInfo)
+        handleRootTaskStart(taskStart)
+      }
+    }
+
+    override def onTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+      val taskSignature = s"${taskEnd.stageId}:${taskEnd.stageAttemptId}:" +
+        s"${taskEnd.taskInfo.index}:${taskEnd.taskInfo.attemptNumber}"
+      logInfo(s"Task End $taskSignature")
+      tasksFinished.add(taskSignature)
+      if (isRootStageId(taskEnd.stageId)) {
+        rootTasksEnded.add(taskEnd.taskInfo)
+        handleRootTaskEnd(taskEnd)
+      }
+    }
+
+    def getTasksFinishedEnsuringCleanJobRun(): Seq[String] = {
+      assert(jobDone.get(), "Job isn't successfully done yet")
+      validate()
+      tasksFinished.asScala.toSeq
+    }
+  }
+
+  private def getExecutorToWorkerAssignments: Map[String, WorkerInfo] = {
+    val executorIdToWorkerInfo = mutable.HashMap[String, WorkerInfo]()
+    master.workers.foreach { wi =>
+      assert(wi.executors.size <= 1, "There should be at most one executor per 
worker")
+      // Cast the executorId to string since the TaskInfo.executorId is a 
string
+      wi.executors.values.foreach { e =>
+        val executorIdString = e.id.toString
+        val oldWorkerInfo = executorIdToWorkerInfo.put(executorIdString, wi)
+        assert(oldWorkerInfo.isEmpty,
+          s"Executor $executorIdString already present on another worker 
${oldWorkerInfo}")
+      }
+    }
+    executorIdToWorkerInfo.toMap
+  }
+
+  private def appConf: SparkConf = {

Review comment:
       Ok, I would get rid of this method and would use just one `SparkConf`. 
It should be created in the `beforeEach`.
   Please move the `securityManager` initialization there too and there you can 
set the master URL too. 
     

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)
+    val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+    val taskIdsKilled = new ConcurrentHashMap[Long, Boolean]
+    val listener = new RootStageAwareListener {
+      override def handleRootTaskStart(taskStart: SparkListenerTaskStart): 
Unit = {
+        val taskInfo = taskStart.taskInfo
+        if (taskIdsKilled.size() < numTimesToKillWorkers) {
+          val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+          decommissionWorkerOnMaster(workerInfo, "partition 0 must die")
+          killWorkerAfterTimeout(workerInfo, 1)
+          taskIdsKilled.put(taskInfo.taskId, true)
+        }
+      }
+
+      override def validate(): Unit = {
+        rootTasksStarted.asScala.foreach { taskInfo =>
+          assert(taskInfo.index == 0, s"Unknown task index ${taskInfo.index}")
+        }
+        rootTasksEnded.asScala.foreach { taskInfo =>
+          assert(taskInfo.index === 0, s"Expected task index ${taskInfo.index} 
to be 0")
+          // If a task has been killed then it shouldn't be successful
+          val taskSuccessExpected = 
!taskIdsKilled.getOrDefault(taskInfo.taskId, false)
+          val taskSuccessActual = taskInfo.successful
+          assert(taskSuccessActual === taskSuccessExpected,
+            s"Expected task success $taskSuccessActual == 
$taskSuccessExpected")
+        }
+      }
+    }
+    TestUtils.withListener(sc, listener) { _ =>
+      val jobResult = sc.parallelize(1 to 1, 1).map { _ =>
+        Thread.sleep(5 * 1000L); 1
+      }.count()
+      assert(jobResult === 1)
+    }
+    // single task job that gets to run numTimesToKillWorkers + 1 times.
+    assert(listener.getTasksFinishedEnsuringCleanJobRun().size === 
numTimesToKillWorkers + 1)
+  }
+
+  test("decommission workers ensure that shuffle output is regenerated even 
with shuffle service") {
+    val conf = appConf
+    conf.set(config.Tests.TEST_NO_STAGE_RETRY, true)
+    conf.set(config.SHUFFLE_MANAGER, "sort")
+    conf.set(config.SHUFFLE_SERVICE_ENABLED, true)
+    createWorkers(2)
+    val ss = new ExternalShuffleServiceHolder(conf)
+    sc = createSparkContext(conf)
+
+    // Here we will create a 2 stage job: The first stage will have two tasks 
and the second stage
+    // will have one task. The two tasks in the first stage will be long and 
short. We decommission
+    // and kill the worker after the short task is done. Eventually the driver 
should get the
+    // executor lost signal for the short task executor. This should trigger 
regenerating
+    // the shuffle output since we cleanly decommissioned the executor, 
despite running with an
+    // external shuffle service.
+    try {
+      val executorIdToWorkerInfo = getExecutorToWorkerAssignments
+      val workerForTask0Decommissioned = new AtomicBoolean(false)
+      // single task job
+      val listener = new RootStageAwareListener {
+        override def validate(): Unit = {
+          rootTasksStarted.asScala.foreach { taskInfo =>
+            assert(taskInfo.index <= 1, s"Expected ${taskInfo.index} <= 1")
+            assert(taskInfo.successful, s"Task ${taskInfo.index} should be 
successful")
+          }
+          val tasksEnded = rootTasksEnded.asScala
+          tasksEnded.filter(_.index != 0).foreach { taskInfo =>
+            assert(taskInfo.attemptNumber === 0, "2nd task should succeed on 
1st attempt")
+          }
+          val firstTaskAttempts = tasksEnded.filter(_.index == 0)
+          assert(firstTaskAttempts.size > 1, s"Task 0 should have multiple 
attempts")
+        }
+
+        override def handleRootTaskEnd(taskEnd: SparkListenerTaskEnd): Unit = {
+          val taskInfo = taskEnd.taskInfo
+          if (taskInfo.index == 0) {
+            if (workerForTask0Decommissioned.compareAndSet(false, true)) {
+              val workerInfo = executorIdToWorkerInfo(taskInfo.executorId)
+              decommissionWorkerOnMaster(workerInfo, "Kill early done map 
worker")
+              killWorkerAfterTimeout(workerInfo, 0)
+              logInfo(s"Killed the node ${workerInfo.hostPort} that was 
running the early task")
+            }
+          }
+        }
+      }
+      TestUtils.withListener(sc, listener) { _ =>
+        val jobResult = sc.parallelize(1 to 2, 2).mapPartitionsWithIndex((pid, 
_) => {
+          val sleepTimeSeconds = if (pid == 0) 1 else 10
+          Thread.sleep(sleepTimeSeconds * 1000L)
+          List(1).iterator
+        }, preservesPartitioning = true).repartition(1).sum()
+        assert(jobResult === 2)
+      }
+      val tasksSeen = listener.getTasksFinishedEnsuringCleanJobRun()
+      // 4 tasks: 2 from first stage, one retry due to decom, one more from 
the second stage.
+      assert(tasksSeen.size === 4, s"Expected at least 4 tasks but got 
$tasksSeen")

Review comment:
       ```suggestion
         assert(tasksSeen.size === 4, s"Expected 4 tasks but got $tasksSeen")
   ```

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}
+import org.apache.spark.shuffle.FetchFailedException
+import org.apache.spark.storage.BlockManagerId
+import org.apache.spark.util.Utils
+
+class DecommissionWorkerSuite
+  extends SparkFunSuite
+    with Logging
+    with LocalSparkContext
+    with BeforeAndAfterEach {
+
+  private val conf = new 
SparkConf().set(config.Worker.WORKER_DECOMMISSION_ENABLED, true)
+  private val securityManager = new SecurityManager(conf)
+
+  private var masterRpcEnv: RpcEnv = null
+  private var master: Master = null
+  private val workerIdToRpcEnvs: mutable.HashMap[String, RpcEnv] = 
mutable.HashMap.empty
+  private val workers: mutable.ArrayBuffer[Worker] = mutable.ArrayBuffer.empty
+
+  override def beforeEach(): Unit = {
+    super.beforeEach()
+    masterRpcEnv = RpcEnv.create(Master.SYSTEM_NAME, "localhost", 0, conf, 
securityManager)
+    master = makeMaster()
+  }
+
+  override def afterEach(): Unit = {
+    try {
+      masterRpcEnv.shutdown()
+      workerIdToRpcEnvs.values.foreach(_.shutdown())
+      workerIdToRpcEnvs.clear()
+      master.stop()
+      workers.foreach(_.stop())
+      workers.clear()
+      masterRpcEnv = null
+    } finally {
+      super.afterEach()
+    }
+  }
+
+  test("decommission workers should not result in job failure") {
+    val maxTaskFailures = 2
+    conf.set(config.TASK_MAX_FAILURES, maxTaskFailures)
+    val numTimesToKillWorkers = maxTaskFailures + 1
+    val numWorkers = numTimesToKillWorkers + 1
+    createWorkers(numWorkers)
+
+    // Here we will have a single task job and we will keep decommissioning 
(and killing) the
+    // worker running that task K times. Where K is more than the 
maxTaskFailures. Since the worker
+    // is notified of the decommissioning, the task failures can be ignored 
and not fail
+    // the job.
+
+    sc = createSparkContext(appConf)

Review comment:
       By commenting out temporary the `decommissionWorkerOnMaster ` and let 
the `killWorkerAfterTimeout ` does his job.

##########
File path: 
core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala
##########
@@ -939,12 +941,43 @@ private[spark] class TaskSchedulerImpl(
 
   override def executorDecommission(
       executorId: String, decommissionInfo: ExecutorDecommissionInfo): Unit = {
+    synchronized {
+      // Don't bother noting decommissioning for executors that we don't know 
about
+      if (executorIdToHost.contains(executorId)) {
+        // The scheduler can get multiple decommission updates from multiple 
sources,
+        // and some of those can have isHostDecommissioned false. We merge 
them such that
+        // if we heard isHostDecommissioned ever true, then we keep that one 
since it is
+        // most likely coming from the cluster manager and thus authoritative
+        val oldDecomInfo = executorsPendingDecommission.get(executorId)
+        if (oldDecomInfo.isEmpty || !oldDecomInfo.get.isHostDecommissioned) {
+          executorsPendingDecommission(executorId) = decommissionInfo
+        }
+      }
+    }
     rootPool.executorDecommission(executorId)
     backend.reviveOffers()
   }
 
-  override def executorLost(executorId: String, reason: ExecutorLossReason): 
Unit = {
+  override def getExecutorDecommissionInfo(executorId: String)
+    : Option[ExecutorDecommissionInfo] = synchronized {
+      executorsPendingDecommission.get(executorId)
+  }
+
+  override def executorLost(executorId: String, givenReason: 
ExecutorLossReason): Unit = {
     var failedExecutor: Option[String] = None
+    val reason = givenReason match {
+      // Handle executor process loss due to decommissioning
+      case ExecutorProcessLost(message, workerLost, causedByApp) =>

Review comment:
       Nit: `workerLost` => 'origWorkerLost' , `causedByApp` => 
`origCausedByApp`

##########
File path: 
core/src/test/scala/org/apache/spark/deploy/DecommissionWorkerSuite.scala
##########
@@ -0,0 +1,420 @@
+/*
+ * 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.deploy
+
+import java.util.concurrent.{ConcurrentHashMap, ConcurrentLinkedQueue}
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable
+import scala.concurrent.duration._
+
+import org.scalatest.BeforeAndAfterEach
+import org.scalatest.concurrent.Eventually._
+
+import org.apache.spark._
+import org.apache.spark.deploy.DeployMessages.{MasterStateResponse, 
RequestMasterState, WorkerDecommission}
+import org.apache.spark.deploy.master.{ApplicationInfo, Master, WorkerInfo}
+import org.apache.spark.deploy.worker.Worker
+import org.apache.spark.internal.{config, Logging}
+import org.apache.spark.network.TransportContext
+import org.apache.spark.network.netty.SparkTransportConf
+import org.apache.spark.network.shuffle.ExternalBlockHandler
+import org.apache.spark.rpc.{RpcAddress, RpcEnv}
+import org.apache.spark.scheduler.{JobSucceeded, SparkListener, 
SparkListenerJobEnd, SparkListenerStageSubmitted, SparkListenerTaskEnd, 
SparkListenerTaskStart, TaskInfo}

Review comment:
       Nit: Use the wildcard import (`_`)
   https://github.com/databricks/scala-style-guide#imports 




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