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https://issues.apache.org/jira/browse/HADOOP-2131?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12556558#action_12556558
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Hadoop QA commented on HADOOP-2131:
-----------------------------------
-1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12372604/patch-2131.txt
against trunk revision .
@author +1. The patch does not contain any @author tags.
javadoc +1. The javadoc tool did not generate any warning messages.
javac +1. The applied patch does not generate any new compiler warnings.
findbugs +1. The patch does not introduce any new Findbugs warnings.
core tests +1. The patch passed core unit tests.
contrib tests -1. The patch failed contrib unit tests.
Test results:
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/1498/testReport/
Findbugs warnings:
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/1498/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results:
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/1498/artifact/trunk/build/test/checkstyle-errors.html
Console output:
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/1498/console
This message is automatically generated.
> Speculative execution should be allowed for reducers only
> ---------------------------------------------------------
>
> Key: HADOOP-2131
> URL: https://issues.apache.org/jira/browse/HADOOP-2131
> Project: Hadoop
> Issue Type: Improvement
> Components: mapred
> Environment: Hadoop job, map fetches data from external systems
> Reporter: Srikanth Kakani
> Assignee: Amareshwari Sri Ramadasu
> Priority: Critical
> Fix For: 0.16.0
>
> Attachments: patch-2131.txt
>
>
> Consider hadoop jobs where maps fetch data from external systems, and emit
> the data. The reducers in this are identity reducers. The data processed by
> these jobs is huge. There could be slow nodes in this cluster and some of the
> reducers run twice as slow as their counterparts. This could result in a long
> tail. Speculative execution would help greatly in such cases. However given
> the current hadoop, we have to select speculative execution for both maps and
> reducers. In this case hurting the map performance as they are fetching data
> from external systems thereby overloading the external systems.
> Speculative execution only on reducers would be a great way to solve this
> problem.
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