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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13480) ShortCircuitConnection doesn't short-circuit all calls as expected
Date Tue, 11 Aug 2015 16:02:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14681987#comment-14681987
] 

Josh Elser commented on HBASE-13480:
------------------------------------

Hi [~jingcheng.du@intel.com]. I'd have to look at the code again, but your suggestion does
sound reasonable. I'm not sure if there are other locations lurking around in the code which
would have this problem. I'm wondering if Enis' suggestion of ConnectionAdapter extending
ConnectionImplementation instead is the less-error-prone approach. If we can make sure we
pass around the ability to shortcircuit, that should reduce the change to make sure we use
the SCC when we can.

> ShortCircuitConnection doesn't short-circuit all calls as expected
> ------------------------------------------------------------------
>
>                 Key: HBASE-13480
>                 URL: https://issues.apache.org/jira/browse/HBASE-13480
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>    Affects Versions: 1.0.0, 2.0.0, 1.1.0
>            Reporter: Josh Elser
>            Assignee: Josh Elser
>             Fix For: 2.0.0, 1.3.0, 1.2.1, 1.0.3, 1.1.3
>
>
> Noticed the following situation in debugging unexpected unit tests failures in HBASE-13351.
> {{ConnectionUtils#createShortCircuitHConnection(Connection, ServerName, AdminService.BlockingInterface,
ClientService.BlockingInterface)}} is intended to avoid the extra RPC by calling the server's
instantiation of the protobuf rpc stub directly for the AdminService and ClientService.
> The problem is that this is insufficient to actually avoid extra "remote" RPCs as all
other calls to the Connection are routed to a "real" Connection instance. As such, any object
created by the "real" Connection (such as an HTable) will use the real Connection, not the
SSC.
> The end result is that {{MasterRpcService#reportRegionStateTransition(RpcController,
ReportRegionStateTransitionRequest)}} will make additional "remote" RPCs over what it thinks
is an SSC through a {{Get}} on {{HTable}} which was constructed using the SSC, but the {{Get}}
itself will use the underlying real Connection instead of the SSC. With insufficiently sized
thread pools, this has been observed to result in RPC deadlock in the HMaster where an RPC
attempts to make another RPC but there are no more threads available to service the second
RPC so the first RPC blocks indefinitely.



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