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https://issues.apache.org/jira/browse/YARN-2410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14628840#comment-14628840
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Hadoop QA commented on YARN-2410:
---------------------------------

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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | pre-patch |  15m 25s | Pre-patch trunk compilation is 
healthy. |
| {color:green}+1{color} | @author |   0m  0s | The patch does not contain any 
@author tags. |
| {color:green}+1{color} | tests included |   0m  0s | The patch appears to 
include 1 new or modified test files. |
| {color:green}+1{color} | javac |   7m 43s | There were no new javac warning 
messages. |
| {color:green}+1{color} | javadoc |   9m 37s | There were no new javadoc 
warning messages. |
| {color:green}+1{color} | release audit |   0m 22s | The applied patch does 
not increase the total number of release audit warnings. |
| {color:red}-1{color} | checkstyle |   0m 21s | The applied patch generated  
32 new checkstyle issues (total was 60, now 92). |
| {color:green}+1{color} | whitespace |   0m  0s | The patch has no lines that 
end in whitespace. |
| {color:green}+1{color} | install |   1m 23s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 32s | The patch built with 
eclipse:eclipse. |
| {color:red}-1{color} | findbugs |   0m 48s | The patch appears to introduce 4 
new Findbugs (version 3.0.0) warnings. |
| {color:green}+1{color} | mapreduce tests |   0m 26s | Tests passed in 
hadoop-mapreduce-client-shuffle. |
| | |  36m 40s | |
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|| Reason || Tests ||
| FindBugs | module:hadoop-mapreduce-client-shuffle |
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|| Subsystem || Report/Notes ||
| Patch URL | 
http://issues.apache.org/jira/secure/attachment/12745525/YARN-2410-v3.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / 3ec0a04 |
| checkstyle |  
https://builds.apache.org/job/PreCommit-YARN-Build/8551/artifact/patchprocess/diffcheckstylehadoop-mapreduce-client-shuffle.txt
 |
| Findbugs warnings | 
https://builds.apache.org/job/PreCommit-YARN-Build/8551/artifact/patchprocess/newPatchFindbugsWarningshadoop-mapreduce-client-shuffle.html
 |
| hadoop-mapreduce-client-shuffle test log | 
https://builds.apache.org/job/PreCommit-YARN-Build/8551/artifact/patchprocess/testrun_hadoop-mapreduce-client-shuffle.txt
 |
| Test Results | 
https://builds.apache.org/job/PreCommit-YARN-Build/8551/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf902.gq1.ygridcore.net 3.13.0-36-lowlatency #63-Ubuntu SMP 
PREEMPT Wed Sep 3 21:56:12 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux |
| Console output | 
https://builds.apache.org/job/PreCommit-YARN-Build/8551/console |


This message was automatically generated.

> Nodemanager ShuffleHandler can possible exhaust file descriptors
> ----------------------------------------------------------------
>
>                 Key: YARN-2410
>                 URL: https://issues.apache.org/jira/browse/YARN-2410
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>    Affects Versions: 2.5.0
>            Reporter: Nathan Roberts
>            Assignee: Kuhu Shukla
>             Fix For: 2.7.2
>
>         Attachments: YARN-2410-v1.patch, YARN-2410-v2.patch, 
> YARN-2410-v3.patch
>
>
> The async nature of the shufflehandler can cause it to open a huge number of
> file descriptors, when it runs out it crashes.
> Scenario:
> Job with 6K reduces, slow start set to 0.95, about 40 map outputs per node.
> Let's say all 6K reduces hit a node at about same time asking for their
> outputs. Each reducer will ask for all 40 map outputs over a single socket in 
> a
> single request (not necessarily all 40 at once, but with coalescing it is
> likely to be a large number).
> sendMapOutput() will open the file for random reading and then perform an 
> async transfer of the particular portion of this file(). This will 
> theoretically
> happen 6000*40=240000 times which will run the NM out of file descriptors and 
> cause it to crash.
> The algorithm should be refactored a little to not open the fds until they're
> actually needed. 



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