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Date: Fri, 14 Sep 2007 12:22:32 -0700 (PDT)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-1874) lost task trackers -- jobs hang
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     [ https://issues.apache.org/jira/browse/HADOOP-1874?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Raghu Angadi updated HADOOP-1874:
---------------------------------

    Attachment: server-throttle-hack.patch

If things don't improve, I would suggest trying server-throttle-hack.patch, with default queue size of 100 per handler. It slows down reading new requests instead of dropping the earliest requests. This should avoid large spikes in calls dropped.

> 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.1.patch, lazy-dfs-ops.patch, server-throttle-hack.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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