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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-1965) IPCs done using block token-based tickets can't reuse connections
Date Thu, 19 May 2011 22:15:47 GMT
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

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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