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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4676) Foreman.moveToState can block forever if called by the foreman thread while the query is still being setup
Date Mon, 16 May 2016 21:38:12 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15285370#comment-15285370

ASF GitHub Bot commented on DRILL-4676:

Github user hnfgns commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/work/foreman/Foreman.java
    @@ -1221,6 +1223,12 @@ public void interrupted(final InterruptedException e) {
          *   to the user
         public void moveToState(final QueryState newState, final Exception ex) {
    +      // if the current thread is the foreman thread, throw an exception
    +      // otherwise the foreman will be blocked forever on acceptExternalEvents
    +      if (myThreadRef == Thread.currentThread()) {
    --- End diff --
    Let me ask you this: what was the primary cause of deadlock came out of your investigation?

> Foreman.moveToState can block forever if called by the foreman thread while the query
is still being setup
> ----------------------------------------------------------------------------------------------------------
>                 Key: DRILL-4676
>                 URL: https://issues.apache.org/jira/browse/DRILL-4676
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Flow
>    Affects Versions: 1.6.0
>            Reporter: Deneche A. Hakim
>            Assignee: Sudheesh Katkam
>             Fix For: 1.7.0
> When the query is being setup, foreman has a special CountDownLatch that blocks rpc threads
from delivering external events, this latch is unblocked at the end of the query setup.
> In some cases though, when the foreman is submitting remote fragments, a failure in RpcBus.send()
causes an exception to be thrown that is reported to 
> Foreman.FragmentSubmitListener and blocks in the CountDownLatch. This causes the foreman
thread to block forever, and can rpc threads to be blocked too.
> This seems to happen more frequently at a high concurrency load, and also can prevent
clients from connecting to the Drillbits.

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