Github user lirui-intel commented on the pull request:
https://github.com/apache/spark/pull/892#issuecomment-44356508
If I understand, the application cannot control how many executors to
launch (at least with the standalone mode). New executors can be launched for
the application whenever the standalone master schedules resources. So I
suppose it's difficult for the user to determine when he/she gets "enough"
executors.
Another possible way to solve this issue is that when the TaskScheduler
finds new executors/hosts in the resource offer, it can inform the
TaskSetManager to re-compute the pending lists. TaskSetManager currently
handles event like "executor lost", maybe it should also handle "executor
added"?
I have another concern about pendingTasksWithNoPrefs in TaskSetManager.
This list now contains two kinds of tasks: tasks that truly have no preferred
locations, and tasks whose preferred locations are not available. Tasks in this
list are considered as PROCESS_LOCAL, which means they take precedence over
tasks in NODE_LOCAL and RACK_LOCAL lists. Therefore in some scenario (the
allowed locality is PROCESS_LOCAL), TaskSetManager may prefer tasks whose
desired location is unavailable, to tasks that can run with some locality. Not
sure if this behavior is intended?
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