IPCs done using block token-based tickets can't reuse connections
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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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