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From "Apache Spark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-13279) Spark driver stuck holding a global lock when there are 200k tasks submitted in a stage
Date Thu, 11 Feb 2016 06:00:21 GMT

    [ https://issues.apache.org/jira/browse/SPARK-13279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15142286#comment-15142286
] 

Apache Spark commented on SPARK-13279:
--------------------------------------

User 'sitalkedia' has created a pull request for this issue:
https://github.com/apache/spark/pull/11167

> Spark driver stuck holding a global lock when there are 200k tasks submitted in a stage
> ---------------------------------------------------------------------------------------
>
>                 Key: SPARK-13279
>                 URL: https://issues.apache.org/jira/browse/SPARK-13279
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>    Affects Versions: 1.6.0
>            Reporter: Sital Kedia
>             Fix For: 1.6.0
>
>
> While running a large pipeline with 200k tasks, we found that the executors were not
able to register with the driver because the driver was stuck holding a global lock in TaskSchedulerImpl.submitTasks
function. 
> jstack of the driver - http://pastebin.com/m8CP6VMv
> executor log - http://pastebin.com/2NPS1mXC
> From the jstack I see that the thread handing the resource offer from executors (dispatcher-event-loop-9)
is blocked on a lock held by the thread "dag-scheduler-event-loop", which is iterating over
an entire ArrayBuffer when adding a pending tasks. So when we have 200k pending tasks, because
of this o(n2) operations, the driver is just hung for more than 5 minutes. 
> Solution -   In addPendingTask function, we don't really need a duplicate check. It's
okay if we add a task to the same queue twice because dequeueTaskFromList will skip already-running
tasks. 
> Please note that this is a regression from Spark 1.5.



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