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https://issues.apache.org/jira/browse/YARN-547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13632711#comment-13632711
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Hadoop QA commented on YARN-547:
--------------------------------
{color:green}+1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12578908/yarn-547-20130416.1.patch
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:green}+1 tests included{color}. The patch appears to include 3 new
or modified test files.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-YARN-Build/747//testReport/
Console output: https://builds.apache.org/job/PreCommit-YARN-Build/747//console
This message is automatically generated.
> Race condition in Public / Private Localizer may result into resource getting
> downloaded again
> ----------------------------------------------------------------------------------------------
>
> Key: YARN-547
> URL: https://issues.apache.org/jira/browse/YARN-547
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Omkar Vinit Joshi
> Assignee: Omkar Vinit Joshi
> Attachments: yarn-547-20130411.1.patch, yarn-547-20130411.patch,
> yarn-547-20130412.patch, yarn-547-20130415.patch, yarn-547-20130416.1.patch,
> yarn-547-20130416.patch
>
>
> Public Localizer :
> At present when multiple containers try to request a localized resource
> * If the resource is not present then first it is created and Resource
> Localization starts ( LocalizedResource is in DOWNLOADING state)
> * Now if in this state multiple ResourceRequestEvents arrive then
> ResourceLocalizationEvents are sent for all of them.
> Most of the times it is not resulting into a duplicate resource download but
> there is a race condition present there. Inside ResourceLocalization (for
> public download) all the requests are added to local attempts map. If a new
> request comes in then first it is checked in this map before a new download
> starts for the same. For the current download the request will be there in
> the map. Now if a same resource request comes in then it will rejected (i.e.
> resource is getting downloaded already). However if the current download
> completes then the request will be removed from this local map. Now after
> this removal if the LocalizerRequestEvent comes in then as it is not present
> in local map the resource will be downloaded again.
> PrivateLocalizer :
> Here a different but similar race condition is present.
> * Here inside findNextResource method call; each LocalizerRunner tries to
> grab a lock on LocalizerResource. If the lock is not acquired then it will
> keep trying until the resource state changes to LOCALIZED. This lock will be
> released by the LocalizerRunner when download completes.
> * Now if another ContainerLocalizer tries to grab the lock on a resource
> before LocalizedResource state changes to LOCALIZED then resource will be
> downloaded again.
> At both the places the root cause of this is that all the threads try to
> acquire the lock on resource however current state of the LocalizedResource
> is not taken into consideration.
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