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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1965) IPCs done using block token-based tickets can't reuse connections
Date Fri, 20 May 2011 21:28:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13037095#comment-13037095
] 

Tsz Wo (Nicholas), SZE commented on HDFS-1965:
----------------------------------------------

> Turns out the reason that RPC.stopProxy isn't effective in "real life" is that the WritableRpcEngine
"Client" objects are cached in ClientCache with keys that aren't tied to principals. So, stopProxy
doesn't actually cause the connection to disconnect. I'm not sure if that's a bug or by design.

Todd, just saw you comments.  I think this is the real bug: we should fix {{stopProxy(..)}}
instead of changing max idle time.

> IPCs done using block token-based tickets can't reuse connections
> -----------------------------------------------------------------
>
>                 Key: HDFS-1965
>                 URL: https://issues.apache.org/jira/browse/HDFS-1965
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: security
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.22.0
>
>         Attachments: hdfs-1965.txt, hdfs-1965.txt
>
>
> This is the reason that TestFileConcurrentReaders has been failing a lot. Reproducing
a comment from HDFS-1057:
> The test has a thread which continually re-opens the file which is being written to.
Since the file's in the middle of being written, it makes an RPC to the DataNode in order
to determine the visible length of the file. This RPC is authenticated using the block token
which came back in the LocatedBlocks object as the security ticket.
> When this RPC hits the IPC layer, it looks at its existing connections and sees none
that can be re-used, since the block token differs between the two requesters. Hence, it reconnects,
and we end up with hundreds or thousands of IPC connections to the datanode.

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