[jira] [Assigned] (SPARK-21991) [LAUNCHER] LauncherServer acceptConnections thread sometime dies if machine has very high load

["Apache Spark (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-21991?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-21991:
------------------------------------

    Assignee: Apache Spark

> [LAUNCHER] LauncherServer acceptConnections thread sometime dies if machine has very high load
> ----------------------------------------------------------------------------------------------
>
>                 Key: SPARK-21991
>                 URL: https://issues.apache.org/jira/browse/SPARK-21991
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Submit
>    Affects Versions: 2.0.2, 2.1.0, 2.1.1, 2.2.0
>         Environment: Single node machine running Ubuntu 16.04.2 LTS (4.4.0-79-generic)
> YARN 2.7.2
> Spark 2.0.2
>            Reporter: Andrea Zito
>            Assignee: Apache Spark
>            Priority: Minor
>
> The way the _LauncherServer_ _acceptConnections_ thread schedules client timeouts causes (non-deterministically) the thread to die with the following exception if the machine is under very high load:
> {noformat}
> Exception in thread "LauncherServer-1" java.lang.IllegalStateException: Task already scheduled or cancelled
>         at java.util.Timer.sched(Timer.java:401)
>         at java.util.Timer.schedule(Timer.java:193)
>         at org.apache.spark.launcher.LauncherServer.acceptConnections(LauncherServer.java:249)
>         at org.apache.spark.launcher.LauncherServer.access$000(LauncherServer.java:80)
>         at org.apache.spark.launcher.LauncherServer$1.run(LauncherServer.java:143)
> {noformat}
> The issue is related to the ordering of actions that the _acceptConnections_ thread uses to handle a client connection:
> # create timeout action
> # create client thread
> # start client thread
> # schedule timeout action
> Under normal conditions the scheduling of the timeout action happen before the client thread has a chance to start, however if the machine is under very high load the client thread can receive CPU time before the timeout action gets scheduled.
> If this condition happen, the client thread cancel the timeout action (which is not yet been scheduled) and goes on, but as soon as the _acceptConnections_ thread gets the CPU back, it will try to schedule the timeout action (which has already been canceled) thus raising the exception.
> Changing the order in which the client thread gets started and the timeout gets scheduled seems to be sufficient to fix this issue.
> As stated above the issue is non-deterministic, I faced the issue multiple times on a single-node machine submitting a high number of short jobs sequentially, but I couldn't easily create a test reproducing the issue. 



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