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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 21:26:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13037090#comment-13037090

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

It seems that the reasons of {{TestFileConcurrentReader}} failing are:
- The test open many files within a short period of time, says in a few seconds.
- {{DFSClient}} creates a proxy for each open.
- Since the default ipc.client.connection.maxidletime is 10 seconds, so the proxies are not
yet closed.
- Therefore, {{TestFileConcurrentReader}} fails with runtime exceptions (out of descriptors?)

Todd, do you agree?

*Questions*: We already have {{RPC.stopProxy(cdp)}} in a finally-block.  Why the resource
is still not released?  Is it because {{TestFileConcurrentReader}} opens files so fast that
the finally-block is not yet reached?  Or {{RPC.stopProxy(..)}} does not work?

> 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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