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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-2183) Cleaner service for cache manager
Date Wed, 22 Oct 2014 22:30:34 GMT

    [ https://issues.apache.org/jira/browse/YARN-2183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14180676#comment-14180676
] 

Karthik Kambatla commented on YARN-2183:
----------------------------------------

bq. we do have a YARN admin command implemented that lets you run the cleaner task on demand
(YARN-2189). 
Cool. In that case, I see the merit to keeping runCleanerTask around.

bq. this check is needed to prevent a race (i.e. not allow an on-demand run when a scheduled
run is in progress).
I understand we need a check to prevent the race. I wonder if we can just re-use the existing
check in CleanerTask#run instead of an explicit check in CleanerService#runCleanerTask? From
what I remember, that would make the code in CleanerTask#run cleaner as well. (no pun)

bq. However, it’s not clear to me whether a dependency from an SCMStore to an AppChecker
is always a fine requirement for other types of stores.
I poked around a little more, and here is what I think. SharedCacheManager creates an instance
of AppChecker, rest of the SCM pieces (Store, CleanerService) should just use the same instance.
This instance can be passed either in the constructor or through an SCMContext similar to
RMContext. Or, we could add SCM#getAppChecker. 

In its current form, CleanerTask#cleanResourceReferences fetches the references from the store,
checks if the apps are running, and asks the store to remove the references. Moving the whole
method to the store would simplify the code more. 

The latest patch looks pretty good but for the above two points. One other nit: One of {CleanerTask,
CleanerService} has unused imports. 

> Cleaner service for cache manager
> ---------------------------------
>
>                 Key: YARN-2183
>                 URL: https://issues.apache.org/jira/browse/YARN-2183
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Chris Trezzo
>            Assignee: Chris Trezzo
>         Attachments: YARN-2183-trunk-v1.patch, YARN-2183-trunk-v2.patch, YARN-2183-trunk-v3.patch,
YARN-2183-trunk-v4.patch, YARN-2183-trunk-v5.patch
>
>
> Implement the cleaner service for the cache manager along with metrics for the service.
This service is responsible for cleaning up old resource references in the manager and removing
stale entries from the cache.



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