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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2119) JobTracker becomes non-responsive if the task trackers finish task too fast
Date Sat, 09 Feb 2008 08:20:07 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12567287#action_12567287

Amar Kamat commented on HADOOP-2119:

I guess you meant 'spare matrix' conceptually. AFAIK java doesn't have any inbuilt implementation
for sparse matrix. This data structure will be optimized for non-running tasks (virgin + failed)
1) For virgin tasks there are no insertions 
2) For failed tasks we just append in the front. 

Wondering on the following points
1) I am not sure how easy it would be to insert into this structure. 
2) Also how easily we can maintain the sortedness. This would be required for failed/running
3) Also the implementation and space complexity will also be _HIGH_. 

For HADOOP-2014, any of the designs mentioned in the table would work fine with an extra count
(in the TIP) of number of trackers having the split locally. I think the strategy mentioned
] along with (8) [in the above table] for running tasks would be efficient in terms of memory,
space and implementation. Comments?

> 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.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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