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From "Omkar Vinit Joshi (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-547) Race condition in Public / Private Localizer may result into resource getting downloaded again
Date Tue, 16 Apr 2013 00:48:16 GMT

     [ https://issues.apache.org/jira/browse/YARN-547?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Omkar Vinit Joshi updated YARN-547:
-----------------------------------

    Summary: Race condition in Public / Private Localizer may result into resource getting
downloaded again  (was: Race condition in Public Localizer may result into resource getting
downloaded again)
    
> 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
>
>
> 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 come in then ResourceLocalizationEvents
are fired 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 
> The root cause for this is the presence of FetchResourceTransition on receiving ResourceRequestEvent
in DOWNLOADING state.

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