[HDFS-1965] IPCs done using block token-based tickets can't reuse connections - ASF JIRA

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Details

Type: Bug
Status: Closed
Priority: Critical
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 0.22.0
Component/s: security
Labels:
None

Hadoop Flags:

Reviewed

Description

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.