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From "Edward J. Yoon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HAMA-444) All tasks should be finished at the last iteration
Date Mon, 26 Sep 2011 05:53:26 GMT

    [ https://issues.apache.org/jira/browse/HAMA-444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13114475#comment-13114475
] 

Edward J. Yoon commented on HAMA-444:
-------------------------------------

This is not related with ZK race condition issue.

Currently, Child process closes BSPPeer and GroomServer reports TaskStatus when task is done
without error.

{code}
            if (!tip.runner.isAlive()) {
              if (taskStatus.getRunState() != TaskStatus.State.FAILED) {
                taskStatus.setRunState(TaskStatus.State.SUCCEEDED);
              }
              taskStatus.setPhase(TaskStatus.Phase.CLEANUP);
            }
{code}

But, each BSP task can be finished differently. For example, 

{code}
bsp() {
  while(condition is ture) {
    ... local computation
    bsp.send(something, toOtherHost);

    sync();
    if(condition is ture) {
      LOG.info("This task is finished at " + getSuperstepCount());
      break;
    }
  }
}
{code}

In this case, current comparison logic of barrier can be problematic because finished tasks
won't create znode anymore.

> All tasks should be finished at the last iteration
> --------------------------------------------------
>
>                 Key: HAMA-444
>                 URL: https://issues.apache.org/jira/browse/HAMA-444
>             Project: Hama
>          Issue Type: Bug
>          Components: bsp
>    Affects Versions: 0.3.0
>            Reporter: Edward J. Yoon
>             Fix For: 0.4.0
>
>
> Each BSP task can be finished differently with their each conditions. In this case, all
tasks should be finished at the last iteration or comparison logic of barrier should be fixed
to avoid hang problem.

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