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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3373) FileContext HDFS implementation can leak socket caches
Date Fri, 01 Jun 2012 22:03:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287722#comment-13287722

Daryn Sharp commented on HDFS-3373:

On a related tangent, a similar situation causes the NMs to leak sockets due to unclosed {{DistributedFileSystems}}.
 Each one holds a {{DFSClient}} that holds a cache with at least 1 CLOSE_WAIT socket.  The
socket gets closed if/when the {{DFSClient}} looks for a cached socket, but it gets replaced
with another CLOSE_WAIT socket.

With security enabled, a NM leaks 1 socket/user.  With security disabled, a NM will leak *1
socket/job* since the UGI always appears different which causes multiple instances of the
same dfs to pile up in the fs cache.

The UGI/fs-cache is a separate issue, but there should probably be something like another
thread that scans the cached sockets to remove closed ones.  Otherwise {{FileContext}} will
be ill-suited for a daemon that needs to create more than one context since it too will leak
> FileContext HDFS implementation can leak socket caches
> ------------------------------------------------------
>                 Key: HDFS-3373
>                 URL: https://issues.apache.org/jira/browse/HDFS-3373
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 2.0.0-alpha
>            Reporter: Todd Lipcon
>            Assignee: John George
> As noted by Nicholas in HDFS-3359, FileContext doesn't have a close() method, and thus
never calls DFSClient.close(). This means that, until finalizers run, DFSClient will hold
on to its SocketCache object and potentially have a lot of outstanding sockets/fds held on

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