SPARK-1937: fix issue with task locality

Don't check executor/host availability when creating a TaskSetManager. Because the executors may haven't been registered when the TaskSetManager is created, in which case all tasks will be considered "has no preferred locations", and thus losing data locality in later scheduling.

Author: Rui Li <[email protected]>
Author: lirui-intel <[email protected]>

Closes apache#892 from lirui-intel/delaySchedule and squashes the following commits:

8444d7c [Rui Li] fix code style
fafd57f [Rui Li] keep locality constraints within the valid levels
18f9e05 [Rui Li] restrict allowed locality
5b3fb2f [Rui Li] refine UT
99f843e [Rui Li] add unit test and fix bug
fff4123 [Rui Li] fix computing valid locality levels
685ed3d [Rui Li] remove delay shedule for pendingTasksWithNoPrefs
7b0177a [Rui Li] remove redundant code
c7b93b5 [Rui Li] revise patch
3d7da02 [lirui-intel] Update TaskSchedulerImpl.scala
cab4c71 [Rui Li] revised patch
539a578 [Rui Li] fix code style
cf0d6ac [Rui Li] fix code style
3dfae86 [Rui Li] re-compute pending tasks when new host is added
a225ac2 [Rui Li] SPARK-1937: fix issue with task locality

Author: Rui Li

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

@@ -210,11 +210,14 @@ private[spark] class TaskSchedulerImpl(
     SparkEnv.set(sc.env)
 
     // Mark each slave as alive and remember its hostname
+    // Also track if new executor is added
+    var newExecAvail = false
     for (o <- offers) {
       executorIdToHost(o.executorId) = o.host
       if (!executorsByHost.contains(o.host)) {
         executorsByHost(o.host) = new HashSet[String]()
         executorAdded(o.executorId, o.host)
+        newExecAvail = true
       }
     }
 
@@ -227,12 +230,15 @@ private[spark] class TaskSchedulerImpl(
     for (taskSet <- sortedTaskSets) {
       logDebug("parentName: %s, name: %s, runningTasks: %s".format(
         taskSet.parent.name, taskSet.name, taskSet.runningTasks))
+      if (newExecAvail) {
+        taskSet.executorAdded()
+      }
     }
 
     // Take each TaskSet in our scheduling order, and then offer it each node in increasing order
     // of locality levels so that it gets a chance to launch local tasks on all of them.
     var launchedTask = false
-    for (taskSet <- sortedTaskSets; maxLocality <- TaskLocality.values) {
+    for (taskSet <- sortedTaskSets; maxLocality <- taskSet.myLocalityLevels) {
       do {
         launchedTask = false
         for (i <- 0 until shuffledOffers.size) {

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

@@ -118,7 +118,7 @@ private[spark] class TaskSetManager(
   private val pendingTasksForRack = new HashMap[String, ArrayBuffer[Int]]
 
   // Set containing pending tasks with no locality preferences.
-  val pendingTasksWithNoPrefs = new ArrayBuffer[Int]
+  var pendingTasksWithNoPrefs = new ArrayBuffer[Int]
 
   // Set containing all pending tasks (also used as a stack, as above).
   val allPendingTasks = new ArrayBuffer[Int]
@@ -153,8 +153,8 @@ private[spark] class TaskSetManager(
   }
 
   // Figure out which locality levels we have in our TaskSet, so we can do delay scheduling
-  val myLocalityLevels = computeValidLocalityLevels()
-  val localityWaits = myLocalityLevels.map(getLocalityWait) // Time to wait at each level
+  var myLocalityLevels = computeValidLocalityLevels()
+  var localityWaits = myLocalityLevels.map(getLocalityWait) // Time to wait at each level
 
   // Delay scheduling variables: we keep track of our current locality level and the time we
   // last launched a task at that level, and move up a level when localityWaits[curLevel] expires.
@@ -181,16 +181,14 @@ private[spark] class TaskSetManager(
     var hadAliveLocations = false
     for (loc <- tasks(index).preferredLocations) {
       for (execId <- loc.executorId) {
-        if (sched.isExecutorAlive(execId)) {
-          addTo(pendingTasksForExecutor.getOrElseUpdate(execId, new ArrayBuffer))
-          hadAliveLocations = true
-        }
+        addTo(pendingTasksForExecutor.getOrElseUpdate(execId, new ArrayBuffer))
       }
       if (sched.hasExecutorsAliveOnHost(loc.host)) {
-        addTo(pendingTasksForHost.getOrElseUpdate(loc.host, new ArrayBuffer))
-        for (rack <- sched.getRackForHost(loc.host)) {
-          addTo(pendingTasksForRack.getOrElseUpdate(rack, new ArrayBuffer))
-        }
+        hadAliveLocations = true
+      }
+      addTo(pendingTasksForHost.getOrElseUpdate(loc.host, new ArrayBuffer))
+      for (rack <- sched.getRackForHost(loc.host)) {
+        addTo(pendingTasksForRack.getOrElseUpdate(rack, new ArrayBuffer))
         hadAliveLocations = true
       }
     }
@@ -725,10 +723,12 @@ private[spark] class TaskSetManager(
   private def computeValidLocalityLevels(): Array[TaskLocality.TaskLocality] = {
     import TaskLocality.{PROCESS_LOCAL, NODE_LOCAL, RACK_LOCAL, ANY}
     val levels = new ArrayBuffer[TaskLocality.TaskLocality]
-    if (!pendingTasksForExecutor.isEmpty && getLocalityWait(PROCESS_LOCAL) != 0) {
+    if (!pendingTasksForExecutor.isEmpty && getLocalityWait(PROCESS_LOCAL) != 0 &&
+        pendingTasksForExecutor.keySet.exists(sched.isExecutorAlive(_))) {
       levels += PROCESS_LOCAL
     }
-    if (!pendingTasksForHost.isEmpty && getLocalityWait(NODE_LOCAL) != 0) {
+    if (!pendingTasksForHost.isEmpty && getLocalityWait(NODE_LOCAL) != 0 &&
+        pendingTasksForHost.keySet.exists(sched.hasExecutorsAliveOnHost(_))) {
       levels += NODE_LOCAL
     }
     if (!pendingTasksForRack.isEmpty && getLocalityWait(RACK_LOCAL) != 0) {
@@ -738,4 +738,21 @@ private[spark] class TaskSetManager(
     logDebug("Valid locality levels for " + taskSet + ": " + levels.mkString(", "))
     levels.toArray
   }
+
+  // Re-compute pendingTasksWithNoPrefs since new preferred locations may become available
+  def executorAdded() {
+    def newLocAvail(index: Int): Boolean = {
+      for (loc <- tasks(index).preferredLocations) {
+        if (sched.hasExecutorsAliveOnHost(loc.host) ||
+            sched.getRackForHost(loc.host).isDefined) {
+          return true
+        }
+      }
+      false
+    }
+    logInfo("Re-computing pending task lists.")
+    pendingTasksWithNoPrefs = pendingTasksWithNoPrefs.filter(!newLocAvail(_))
+    myLocalityLevels = computeValidLocalityLevels()
+    localityWaits = myLocalityLevels.map(getLocalityWait)
+  }
 }

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

@@ -77,6 +77,10 @@ class FakeTaskScheduler(sc: SparkContext, liveExecutors: (String, String)* /* ex
   override def isExecutorAlive(execId: String): Boolean = executors.contains(execId)
 
   override def hasExecutorsAliveOnHost(host: String): Boolean = executors.values.exists(_ == host)
+
+  def addExecutor(execId: String, host: String) {
+    executors.put(execId, host)
+  }
 }
 
 class TaskSetManagerSuite extends FunSuite with LocalSparkContext with Logging {
@@ -400,6 +404,36 @@ class TaskSetManagerSuite extends FunSuite with LocalSparkContext with Logging {
     assert(sched.taskSetsFailed.contains(taskSet.id))
   }
 
+  test("new executors get added") {
+    sc = new SparkContext("local", "test")
+    val sched = new FakeTaskScheduler(sc)
+    val taskSet = FakeTask.createTaskSet(4,
+      Seq(TaskLocation("host1", "execA")),
+      Seq(TaskLocation("host1", "execB")),
+      Seq(TaskLocation("host2", "execC")),
+      Seq())
+    val clock = new FakeClock
+    val manager = new TaskSetManager(sched, taskSet, MAX_TASK_FAILURES, clock)
+    // All tasks added to no-pref list since no preferred location is available
+    assert(manager.pendingTasksWithNoPrefs.size === 4)
+    // Only ANY is valid
+    assert(manager.myLocalityLevels.sameElements(Array(ANY)))
+    // Add a new executor
+    sched.addExecutor("execD", "host1")
+    manager.executorAdded()
+    // Task 0 and 1 should be removed from no-pref list
+    assert(manager.pendingTasksWithNoPrefs.size === 2)
+    // Valid locality should contain NODE_LOCAL and ANY
+    assert(manager.myLocalityLevels.sameElements(Array(NODE_LOCAL, ANY)))
+    // Add another executor
+    sched.addExecutor("execC", "host2")
+    manager.executorAdded()
+    // No-pref list now only contains task 3
+    assert(manager.pendingTasksWithNoPrefs.size === 1)
+    // Valid locality should contain PROCESS_LOCAL, NODE_LOCAL and ANY
+    assert(manager.myLocalityLevels.sameElements(Array(PROCESS_LOCAL, NODE_LOCAL, ANY)))
+  }
+
   def createTaskResult(id: Int): DirectTaskResult[Int] = {
     val valueSer = SparkEnv.get.serializer.newInstance()
     new DirectTaskResult[Int](valueSer.serialize(id), mutable.Map.empty, new TaskMetrics)