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https://issues.apache.org/jira/browse/HADOOP-2639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12563245#action_12563245
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Arun C Murthy commented on HADOOP-2639:
---------------------------------------
Ok, looks like there is some disconnect...
While implementing HADOOP-2247, I remember that the following code:
{noformat}
float failureRate = (float)fetchFailures / runningReduceTasks;
{noformat}
is to mean: _Check if there are too many currently running reduce TIPs are
complaining about this map._
I had a discussion with Amar and he clarified that he was considering the
counter as _currently running reduce task-attempts_ and not _currently running
reduce TIPs_ as was the original intention... and hence this debate/disconnect.
Given that, I think the right fix is for us to figure _why_ the
*runningReduceTasks* counter is wrongly turning -ve and fix the wrong
decrement...
Thoughts?
> Reducers stuck in shuffle
> -------------------------
>
> Key: HADOOP-2639
> URL: https://issues.apache.org/jira/browse/HADOOP-2639
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Amareshwari Sri Ramadasu
> Assignee: Amar Kamat
> Priority: Blocker
> Fix For: 0.16.0
>
> Attachments: HADOOP-2639.patch
>
>
> I started sort benchmark on 500 nodes. It has 40000 maps and 900 reducers.
> There are 11 reducers stuck in shuffle with 33% progress. I could see a node
> down which ran 80 maps on it. And all these reducers are trying to fetch map
> output from that node.
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