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https://issues.apache.org/jira/browse/YARN-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14306748#comment-14306748
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Sunil G commented on YARN-3136:
-------------------------------
Hi [~rohithsharma]
*getLiveContainers()* is giving a copy as you mentioned. Earlier I was looking
for getter method to fetch FicaSchedulerApp from *applications* with schedule
lock. But that also not needed.
{code}
Map<ApplicationId, SchedulerApplication<T>> applications
this.applications =
new ConcurrentHashMap<ApplicationId,
SchedulerApplication<FiCaSchedulerApp>>();
{code}
*applications* is a concurrent hash map. Hence synchronized can be removed from
*getTransferredContainers* without any change in the method itself. Also as
mentioned by [~jianhe], a check will be added on *registerApplicationMaster()*.
> getTransferredContainers can be a bottleneck during AM registration
> -------------------------------------------------------------------
>
> Key: YARN-3136
> URL: https://issues.apache.org/jira/browse/YARN-3136
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: scheduler
> Affects Versions: 2.6.0
> Reporter: Jason Lowe
> Assignee: Sunil G
>
> While examining RM stack traces on a busy cluster I noticed a pattern of AMs
> stuck waiting for the scheduler lock trying to call getTransferredContainers.
> The scheduler lock is highly contended, especially on a large cluster with
> many nodes heartbeating, and it would be nice if we could find a way to
> eliminate the need to grab this lock during this call. We've already done
> similar work during AM allocate calls to make sure they don't needlessly grab
> the scheduler lock, and it would be good to do so here as well, if possible.
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