Github user dhruve commented on a diff in the pull request:
https://github.com/apache/spark/pull/22288#discussion_r226754849
--- Diff:
core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala ---
@@ -415,9 +420,65 @@ private[spark] class TaskSchedulerImpl(
launchedAnyTask |= launchedTaskAtCurrentMaxLocality
} while (launchedTaskAtCurrentMaxLocality)
}
+
if (!launchedAnyTask) {
- taskSet.abortIfCompletelyBlacklisted(hostToExecutors)
+ taskSet.getCompletelyBlacklistedTaskIfAny(hostToExecutors) match
{
+ case taskIndex: Some[Int] => // Returns the taskIndex which
was unschedulable
+
+ // If the taskSet is unschedulable we try to find an
existing idle blacklisted
+ // executor. If we cannot find one, we abort immediately.
Else we kill the idle
+ // executor and kick off an abortTimer which if it doesn't
schedule a task within the
+ // the timeout will abort the taskSet if we were unable to
schedule any task from the
+ // taskSet.
+ // Note 1: We keep track of schedulability on a per taskSet
basis rather than on a per
+ // task basis.
+ // Note 2: The taskSet can still be aborted when there are
more than one idle
+ // blacklisted executors and dynamic allocation is on. This
can happen when a killed
+ // idle executor isn't replaced in time by
ExecutorAllocationManager as it relies on
+ // pending tasks and doesn't kill executors on idle
timeouts, resulting in the abort
+ // timer to expire and abort the taskSet.
+ executorIdToRunningTaskIds.find(x => !isExecutorBusy(x._1))
match {
+ case Some (x) =>
+ val executorId = x._1
+ if (!unschedulableTaskSetToExpiryTime.contains(taskSet))
{
+ blacklistTrackerOpt.foreach(blt =>
blt.killBlacklistedIdleExecutor(executorId))
+
+ unschedulableTaskSetToExpiryTime(taskSet) =
clock.getTimeMillis()
+ val timeout =
conf.get(config.UNSCHEDULABLE_TASKSET_TIMEOUT) * 1000
+ logInfo(s"Waiting for $timeout ms for completely "
+ + s"blacklisted task to be schedulable again before
aborting $taskSet.")
+ abortTimer.schedule(new TimerTask() {
+ override def run() {
+ if
(unschedulableTaskSetToExpiryTime.contains(taskSet) &&
+ (unschedulableTaskSetToExpiryTime(taskSet) +
timeout)
+ <= clock.getTimeMillis()
+ ) {
+ logInfo("Cannot schedule any task because of
complete blacklisting. " +
+ s"Wait time for scheduling expired. Aborting
$taskSet.")
+
taskSet.abortSinceCompletelyBlacklisted(taskIndex.get)
+ } else {
+ this.cancel()
+ }
+ }
+ }, timeout)
+ }
+ case _ => // Abort Immediately
+ logInfo("Cannot schedule any task because of complete
blacklisting. No idle" +
+ s" executors can be found to kill. Aborting $taskSet."
)
+ taskSet.abortSinceCompletelyBlacklisted(taskIndex.get)
+ }
+ case _ => // Do nothing if no tasks completely blacklisted.
+ }
+ } else {
+ // If a task was scheduled, we clear the expiry time for all the
taskSets. This ensures
+ // that we have got atleast a non blacklisted executor and the
job can progress. The
+ // abort timer checks this entry to decide if we want to abort
the taskSet.
--- End diff --
That is correct. It also covers other scenario that @tgravescs originally
pointed out.
Lets say if you have multiple taskSets running which are completely
blacklisted. If you were able to get an executor, you would just clear the
timer for that specific taskSet. Now due to resource constraint, if you weren't
able to obtain another executor within the timeout for the other taskSet, you
would abort the other taskSet when you could actually wait for it to be
scheduled on the newly obtained executor.
So clearing the timer for all the taskSets ensures that currently we aren't
in a completely blacklisted state and should try to run to completion. However
if the taskset itself is flawed, we would eventually fail. This could result in
wasted effort, but we don't have a way to determine that yet, so this should be
okay.
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