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https://issues.apache.org/jira/browse/HADOOP-1874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12527226
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Devaraj Das commented on HADOOP-1874:
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Right Doug. This is a quick solution that might be taken out later in favor of
better solutions like the one you are talking about.
> lost task trackers -- jobs hang
> -------------------------------
>
> Key: HADOOP-1874
> URL: https://issues.apache.org/jira/browse/HADOOP-1874
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.15.0
> Reporter: Christian Kunz
> Assignee: Devaraj Das
> Priority: Blocker
> Attachments: lazy-dfs-ops.patch
>
>
> This happens on a 1400 node cluster using a recent nightly build patched with
> HADOOP-1763 (that fixes a previous 'lost task tracker' issue) running a
> c++-pipes job with 4200 maps and 2800 reduces. The task trackers start to get
> lost in high numbers at the end of job completion.
> Similar non-pipes job do not show the same problem, but is unclear whether it
> is related to c++-pipes. It could also be dfs overload when reduce tasks
> close and validate all newly created dfs files. I see dfs client rpc timeout
> exception. But this alone does not explain the escalation in losing task
> trackers.
> I also noticed that the job tracker becomes rather unresponsive with rpc
> timeout and call queue overflow exceptions. Job Tracker is running with 60
> handlers.
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