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From pwend...@apache.org
Subject git commit: [SPARK-2204] Launch tasks on the proper executors in mesos fine-grained mode
Date Wed, 25 Jun 2014 20:21:26 GMT
Repository: spark
Updated Branches:
  refs/heads/master 7ff2c754f -> 1132e472e


[SPARK-2204] Launch tasks on the proper executors in mesos fine-grained mode

The scheduler for Mesos in fine-grained mode launches tasks on the wrong executors. `MesosSchedulerBackend.resourceOffers(SchedulerDriver,
List[Offer])` is assuming that `TaskSchedulerImpl.resourceOffers(Seq[WorkerOffer])` is returning
task lists in the same order as the offers it was passed, but in the current implementation
`TaskSchedulerImpl.resourceOffers` shuffles the offers to avoid assigning the tasks always
to the same executors. The result is that the tasks are launched on the wrong executors. The
jobs are sometimes able to complete, but most of the time they fail. It seems that as soon
as something goes wrong with a task for some reason Spark is not able to recover since it's
mistaken as to where the tasks are actually running. Also, it seems that the more the cluster
is under load the more likely the job is to fail because there's a higher probability that
Spark is trying to launch a task on a slave that doesn't actually have enough resources, again
because it's using the 
 wrong offers.

The solution is to not assume that the order in which the tasks are returned is the same as
the offers, and simply launch the tasks on the executor decided by `TaskSchedulerImpl.resourceOffers`.
What I am not sure about is that I considered slaveId and executorId to be the same, which
is true at least in my setup, but I don't know if that is always true.

I tested this on top of the 1.0.0 release and it seems to work fine on our cluster.

Author: Sebastien Rainville <sebastien@hopper.com>

Closes #1140 from sebastienrainville/fine-grained-mode-fix-master and squashes the following
commits:

a98b0e0 [Sebastien Rainville] Use a HashMap to retrieve the offer indices
d6ffe54 [Sebastien Rainville] Launch tasks on the proper executors in mesos fine-grained mode


Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/1132e472
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/1132e472
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/1132e472

Branch: refs/heads/master
Commit: 1132e472eca1a00c2ce10d2f84e8f0e79a5193d3
Parents: 7ff2c75
Author: Sebastien Rainville <sebastien@hopper.com>
Authored: Wed Jun 25 13:21:18 2014 -0700
Committer: Patrick Wendell <pwendell@gmail.com>
Committed: Wed Jun 25 13:21:18 2014 -0700

----------------------------------------------------------------------
 .../cluster/mesos/MesosSchedulerBackend.scala          | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/spark/blob/1132e472/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerBackend.scala
----------------------------------------------------------------------
diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerBackend.scala
b/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerBackend.scala
index a089a02..c717e7c 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerBackend.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosSchedulerBackend.scala
@@ -185,8 +185,8 @@ private[spark] class MesosSchedulerBackend(
       synchronized {
         // Build a big list of the offerable workers, and remember their indices so that
we can
         // figure out which Offer to reply to for each worker
-        val offerableIndices = new ArrayBuffer[Int]
         val offerableWorkers = new ArrayBuffer[WorkerOffer]
+        val offerableIndices = new HashMap[String, Int]
 
         def enoughMemory(o: Offer) = {
           val mem = getResource(o.getResourcesList, "mem")
@@ -195,7 +195,7 @@ private[spark] class MesosSchedulerBackend(
         }
 
         for ((offer, index) <- offers.zipWithIndex if enoughMemory(offer)) {
-          offerableIndices += index
+          offerableIndices.put(offer.getSlaveId.getValue, index)
           offerableWorkers += new WorkerOffer(
             offer.getSlaveId.getValue,
             offer.getHostname,
@@ -206,14 +206,13 @@ private[spark] class MesosSchedulerBackend(
         val taskLists = scheduler.resourceOffers(offerableWorkers)
 
         // Build a list of Mesos tasks for each slave
-        val mesosTasks = offers.map(o => Collections.emptyList[MesosTaskInfo]())
+        val mesosTasks = offers.map(o => new JArrayList[MesosTaskInfo]())
         for ((taskList, index) <- taskLists.zipWithIndex) {
           if (!taskList.isEmpty) {
-            val offerNum = offerableIndices(index)
-            val slaveId = offers(offerNum).getSlaveId.getValue
-            slaveIdsWithExecutors += slaveId
-            mesosTasks(offerNum) = new JArrayList[MesosTaskInfo](taskList.size)
             for (taskDesc <- taskList) {
+              val slaveId = taskDesc.executorId
+              val offerNum = offerableIndices(slaveId)
+              slaveIdsWithExecutors += slaveId
               taskIdToSlaveId(taskDesc.taskId) = slaveId
               mesosTasks(offerNum).add(createMesosTask(taskDesc, slaveId))
             }


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