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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5651) remove dfs.namenode.caching.enabled
Date Fri, 20 Dec 2013 22:00:10 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5651?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13854598#comment-13854598
] 

Andrew Wang commented on HDFS-5651:
-----------------------------------

I read the locking stuff again, and I think you're right. It's hard to win when {{#rescan}}
can potentially be a long operation holding the lock. Only comment is that we should assert
that the FSN locks aren't held in {{waitFor}}, since that'd be an error. Thanks Colin.

> remove dfs.namenode.caching.enabled
> -----------------------------------
>
>                 Key: HDFS-5651
>                 URL: https://issues.apache.org/jira/browse/HDFS-5651
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: 3.0.0
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>         Attachments: HDFS-5651.001.patch, HDFS-5651.002.patch, HDFS-5651.003.patch, HDFS-5651.004.patch,
HDFS-5651.006.patch
>
>
> We can remove dfs.namenode.caching.enabled and simply always enable caching, similar
to how we do with snapshots and other features.  The main overhead is the size of the cachedBlocks
GSet.  However, we can simply make the size of this GSet configurable, and people who don't
want caching can set it to a very small value.



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