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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2119) JobTracker becomes non-responsive if the task trackers finish task too fast
Date Thu, 20 Mar 2008 23:47:24 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12580969#action_12580969

Owen O'Malley commented on HADOOP-2119:

In the JobTracker:
  * siblingSetAtLevel seems really arcane. I would propose that instead you add getChildren
to the Node interface.
  * why is there yet another map from hostname to Node? This is already done in the node mapping.

In the JobInProgress:
  * I'm really concerned that we are adding 5 new fields holding collections to the JobInProgress
  * reducers is a really bad name. I'd suggest runnableReduces or something.
  * nodesToMaps should be runnableMaps
  * Don't use assignment in a parameter to a method in initTasks
  * I'm bothered by all of the checks for null Nodes that just skip the location. I think
it should be a warn in the job tracker logs so that admins can find the problem and should
be the default node/ default rack.
  * Shouldn't we remove the node from the nodesToMaps regardless of the level? Since if it
is running, it is also in the runningMaps list and we can speculate out of there.
  * nodesToMaps being null should be a fatal error
  * nodesToMaps should be a Map<Node,Set<Tip>> rather than a list of tips, so
that we can remove things reasonably fast

i'll look some more tonight.

> JobTracker becomes non-responsive if the task trackers finish task too fast
> ---------------------------------------------------------------------------
>                 Key: HADOOP-2119
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2119
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.16.0
>            Reporter: Runping Qi
>            Assignee: Amar Kamat
>            Priority: Critical
>             Fix For: 0.17.0
>         Attachments: HADOOP-2119-v4.1.patch, HADOOP-2119-v5.1.patch, HADOOP-2119-v5.1.patch,
hadoop-2119.patch, hadoop-jobtracker-thread-dump.txt
> I ran a job with 0 reducer on a cluster with 390 nodes.
> The mappers ran very fast.
> The jobtracker lacks behind on committing completed mapper tasks.
> The number of running mappers displayed on web UI getting bigger and bigger.
> The jos tracker eventually stopped responding to web UI.
> No progress is reported afterwards.
> Job tracker is running on a separate node.
> The job tracker process consumed 100% cpu, with vm size 1.01g (reach the heap space limit).

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