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Date: Fri, 20 May 2011 22:06:47 +0000 (UTC)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1965) IPCs done using block token-based
 tickets can't reuse connections
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    [ https://issues.apache.org/jira/browse/HDFS-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13037113#comment-13037113 ] 

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

Okay, you mean this is a temporary fix.  Sounds good.  Some comments on the patch:

- Instead of changing it to public, we could create add a utility method, say in {{DFSTestUtil}}, for invoking the package private method.
{code}
+  /** Public only for tests */
+  public static ClientDatanodeProtocol createClientDatanodeProtocolProxy(
{code}

- How about putting {{confWithNoIpcIdle}} as a member field?

- Please use {{CommonConfigurationKeysPublic.IPC_CLIENT_CONNECTION_MAXIDLETIME_KEY}} for "ipc.client.connection.maxidletime".

- Please add a comment saying that this is a temporary fix and the corresponding codes should be removed once {{stopProxy(..)}} is fixed.

> 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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