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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2902) Killing a container that is localizing can orphan resources in the DOWNLOADING state
Date Fri, 09 Oct 2015 20:11:06 GMT

    [ https://issues.apache.org/jira/browse/YARN-2902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14951115#comment-14951115
] 

Jason Lowe commented on YARN-2902:
----------------------------------

The key with the new proposal is that the LocalizerRunner thread is the one issuing the deletes
and only after the localizer process exits.

bq. 2. Container is killed. Associated resources are stuck in downloading state and a deletion
task is launched for them.
That deletion task would not be launched because the localizer has not exited.  The LocalizerRunner
will still be waiting on the localizer process to exit.

bq. Localizer doesnt exit immediately as of now when container is killed, even though we interrupt
the thread.
Yes, and that's fine.  We won't issue the deletion requests until the localizer process eventually
exits.

The key is this code in LocalizerRunner:
{code:title=LocalizerRunner}
    public void run() {
      Path nmPrivateCTokensPath = null;
      Throwable exception = null;
      try {
[...localizer pre-startup code removed for brevity...]
        if (dirsHandler.areDisksHealthy()) {
          exec.startLocalizer(new LocalizerStartContext.Builder()
              .setNmPrivateContainerTokens(nmPrivateCTokensPath)
              .setNmAddr(localizationServerAddress)
              .setUser(context.getUser())
              .setAppId(ConverterUtils.toString(context.getContainerId()
                  .getApplicationAttemptId().getApplicationId()))
              .setLocId(localizerId)
              .setDirsHandler(dirsHandler)
              .build());
        } else {
          throw new IOException("All disks failed. "
              + dirsHandler.getDisksHealthReport(false));
        }
      // TODO handle ExitCodeException separately?
      } catch (FSError fe) {
        exception = fe;
      } catch (Exception e) {
        exception = e;
      } finally {
        if (exception != null) {
          LOG.info("Localizer failed", exception);
          // On error, report failure to Container and signal ABORT
          // Notify resource of failed localization
          ContainerId cId = context.getContainerId();
          dispatcher.getEventHandler().handle(new ContainerResourceFailedEvent(
              cId, null, exception.getMessage()));
        }
        for (LocalizerResourceRequestEvent event : scheduled.values()) {
          event.getResource().unlock();
        }
        delService.delete(null, nmPrivateCTokensPath, new Path[] {});
      }
{code}

startLocalizer won't return until the localizer process exits, so when it iterates the {{scheduled}}
map in the finally block to unlock the resources we can issue deletions for the local resource
paths at the same time.


> Killing a container that is localizing can orphan resources in the DOWNLOADING state
> ------------------------------------------------------------------------------------
>
>                 Key: YARN-2902
>                 URL: https://issues.apache.org/jira/browse/YARN-2902
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: nodemanager
>    Affects Versions: 2.5.0
>            Reporter: Jason Lowe
>            Assignee: Varun Saxena
>         Attachments: YARN-2902.002.patch, YARN-2902.03.patch, YARN-2902.04.patch, YARN-2902.05.patch,
YARN-2902.06.patch, YARN-2902.07.patch, YARN-2902.patch
>
>
> If a container is in the process of localizing when it is stopped/killed then resources
are left in the DOWNLOADING state.  If no other container comes along and requests these resources
they linger around with no reference counts but aren't cleaned up during normal cache cleanup
scans since it will never delete resources in the DOWNLOADING state even if their reference
count is zero.



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