Github user lirui-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/892#discussion_r13473499
--- Diff:
core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala ---
@@ -54,8 +54,15 @@ private[spark] class TaskSetManager(
clock: Clock = SystemClock)
extends Schedulable with Logging
{
+ // Remember when this TaskSetManager is created
+ val creationTime = clock.getTime()
val conf = sched.sc.conf
+ // The period we wait for new executors to come up
+ // After this period, tasks in pendingTasksWithNoPrefs will be
considered as PROCESS_LOCAL
+ private val WAIT_NEW_EXEC_TIMEOUT =
conf.getLong("spark.scheduler.waitNewExecutorTime", 3000L)
--- End diff --
This waiting period is only intended for pendingTasksWithNoPrefs. Suppose
pendingTasksWithNoPrefs contains tasks whose preference is unavailable. Within
this waiting period, we want to try pendingTasksForExecutor,
pendingTasksForHost and pendingTasksForRack first because tasks in these lists
do have some locality. And when an executor is added, we remove tasks newly
have locality from pendingTasksWithNoPrefs. Then after the waiting period, we
believe no executor will come for tasks still remain in
pendingTasksWithNoPrefs. So they can be shceduled as PROCESS_LOCAL.
You can see tasks in pendingTasksForHost can still get scheduled even
within the period. We're just holding back on pendingTasksWithNoPrefs. I think
it's better than holding back the whole application and schedule nothing.
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