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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3513) HttpFS should cache filesystems
Date Thu, 07 Jun 2012 16:04:24 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3513?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13291089#comment-13291089
] 

Daryn Sharp commented on HDFS-3513:
-----------------------------------

Would a more general, and possibly simpler solution, be to not disable the fs cache but instead
track the last-use per user?  After the expiration period, the user's cached fs instances
may be closed.  Would this address the comment about worst case the server will have a cached
fs per user?  That scenario will lead to a lot of "leaked" fds because {{DFSClient}} will
have sockets in the TIME_WAIT state (see MAPREDUCE-4323).
                
> HttpFS should cache filesystems
> -------------------------------
>
>                 Key: HDFS-3513
>                 URL: https://issues.apache.org/jira/browse/HDFS-3513
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.0.0-alpha
>            Reporter: Alejandro Abdelnur
>            Assignee: Alejandro Abdelnur
>         Attachments: HDFS-3513.patch, HDFS-3513.patch
>
>
> HttpFS opens and closes a FileSystem instance against the backend filesystem (typically
HDFS) on every request. The FileSystem caching is not used as it does not have expiration/timeout
and filesystem instances in there live forever, for long running services like HttpFS this
is not a good thing as it would keep connections open to the NN.

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