GitHub user CodingCat opened a pull request:
https://github.com/apache/spark/pull/1313
SPARK-2294: fix locality inversion bug in TaskManager
copied from original JIRA
(https://issues.apache.org/jira/browse/SPARK-2294):
If an executor E is free, a task may be speculatively assigned to E when
there are other tasks in the job that have not been launched (at all) yet.
Similarly, a task without any locality preferences may be assigned to E when
there was another NODE_LOCAL task that could have been scheduled.
This happens because TaskSchedulerImpl calls TaskSetManager.resourceOffer
(which in turn calls TaskSetManager.findTask) with increasing locality levels,
beginning with PROCESS_LOCAL, followed by NODE_LOCAL, and so on until the
highest currently allowed level. Now, supposed NODE_LOCAL is the highest
currently allowed locality level. The first time findTask is called, it will be
called with max level PROCESS_LOCAL; if it cannot find any PROCESS_LOCAL tasks,
it will try to schedule tasks with no locality preferences or speculative
tasks. As a result, speculative tasks or tasks with no preferences may be
scheduled instead of NODE_LOCAL tasks.
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I added an additional parameter in resourceOffer and findTask, maxLocality,
indicating when we should consider the tasks without locality preference
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/CodingCat/spark SPARK-2294
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/1313.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1313
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commit 35524413287990734685125ec02eb8dd58f97b12
Author: CodingCat <[email protected]>
Date: 2014-07-07T04:37:06Z
fix locality inversion bug in TaskManager
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