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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3637) Handle localization sym-linking correctly at the YARN level
Date Tue, 12 May 2015 23:36:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-3637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14541010#comment-14541010

Vinod Kumar Vavilapalli commented on YARN-3637:

bq. was the shared cache not completely integrated in 2.7?
>From what I know, we didn't call it ready yet for lack of some security related support.
I marked it as beta in the release note.

> Handle localization sym-linking correctly at the YARN level
> -----------------------------------------------------------
>                 Key: YARN-3637
>                 URL: https://issues.apache.org/jira/browse/YARN-3637
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Chris Trezzo
>            Assignee: Chris Trezzo
>            Priority: Blocker
> The shared cache needs to handle resource sym-linking at the YARN layer. Currently, we
let the application layer (i.e. mapreduce) handle this, but it is probably better for all
applications if it is handled transparently.
> Here is the scenario:
> Imagine two separate jars (with unique checksums) that have the same name job.jar.
> They are stored in the shared cache as two separate resources:
> checksum1/job.jar
> checksum2/job.jar
> A new application tries to use both of these resources, but internally refers to them
as different names:
> foo.jar maps to checksum1
> bar.jar maps to checksum2
> When the shared cache returns the path to the resources, both resources are named the
same (i.e. job.jar). Because of this, when the resources are localized one of them clobbers
the other. This is because both symlinks in the container_id directory are the same name (i.e.
job.jar) even though they point to two separate resource directories.
> Originally we tackled this in the MapReduce client by using the fragment portion of the
resource url. This, however, seems like something that should be solved at the YARN layer.

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