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https://issues.apache.org/jira/browse/MAPREDUCE-3184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13206390#comment-13206390
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Matt Foley commented on MAPREDUCE-3184:
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This patch has been tested at user sites and is believed stable. Nathan
Roberts requested that I include it in 1.0.1, as its absence is causing ops
problems with 1.0.0.
> Improve handling of fetch failures when a tasktracker is not responding on
> HTTP
> -------------------------------------------------------------------------------
>
> Key: MAPREDUCE-3184
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3184
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobtracker
> Affects Versions: 0.20.205.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 1.1.0
>
> Attachments: mr-3184.txt
>
>
> On a 100 node cluster, we had an issue where one of the TaskTrackers was hit
> by MAPREDUCE-2386 and stopped responding to fetches. The behavior observed
> was the following:
> - every reducer would try to fetch the same map task, and fail after ~13
> minutes.
> - At that point, all reducers would report this failed fetch to the JT for
> the same task, and the task would be re-run.
> - Meanwhile, the reducers would move on to the next map task that ran on the
> TT, and hang for another 13 minutes.
> The job essentially made no progress for hours, as each map task that ran on
> the bad node was serially marked failed.
> To combat this issue, we should introduce a second type of failed fetch
> notification, used when the TT does not respond at all (ie
> SocketTimeoutException, etc). These fetch failure notifications should count
> against the TT at large, rather than a single task. If more than half of the
> reducers report such an issue for a given TT, then all of the tasks from that
> TT should be re-run.
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