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From kayousterhout <>
Subject [GitHub] spark pull request #13603: [SPARK-15865][CORE] Blacklist should not result i...
Date Tue, 14 Jun 2016 22:32:51 GMT
Github user kayousterhout commented on a diff in the pull request:
    --- Diff: core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala ---
    @@ -280,10 +280,54 @@ private[spark] class TaskSchedulerImpl(
    +    if (!launchedTask && isTaskSetCompletelyBlacklisted(taskSet)) {
    +      taskSet.abort(s"Aborting ${taskSet.taskSet} because it has a task which cannot
be scheduled" +
    +        s" on any executor due to blacklists.")
    +    }
         return launchedTask
    +   * Check whether the given task set has been blacklisted to the point that it can't
run anywhere.
    +   *
    +   * It is possible that this taskset has become impossible to schedule *anywhere* due
to the
    +   * blacklist.  The most common scenario would be if there are fewer executors than
    +   * spark.task.maxFailures. We need to detect this so we can fail the task set, otherwise
the job
    +   * will hang.
    +   *
    +   * The check here is a balance between being sure to catch the issue, but not wasting
    +   * too much time inside the scheduling loop.  Just check if the last task is schedulable
    +   * on any of the available executors.  So this is O(numExecutors) worst-case, but it'll
    +   * really be fast unless you've got a bunch of things blacklisted.  Its possible it
won't detect
    +   * the unschedulable task immediately, but if it returns false, there is at least *some*
    +   * that is schedulable, and after scheduling all of those, we'll eventually find the
    +   * task.
    +   */
    +  private[scheduler] def isTaskSetCompletelyBlacklisted(
    --- End diff --
    Ah got it -- agree that in the long term, given the new blacklistling, it might make sense
here! But let's put it in the TaskSetManager for now.

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