[jira] [Commented] (HBASE-3787) Increment is non-idempotent but client retries RPC

["Andrew Purtell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13566821#comment-13566821 ] 

Andrew Purtell commented on HBASE-3787:
---------------------------------------

I think this has come up again on the user list. See http://search-hadoop.com/m/3naHBtQZV51/. Since we can easily change the on wire RPC format of various operations for 0.96, now is a good time to look at this. A solution might be to introduce a nonce (generated internally by the client) on non-idempotent operations to convert them into idempotent ones. Not sure exactly how that would work server side.
                
> Increment is non-idempotent but client retries RPC
> --------------------------------------------------
>
>                 Key: HBASE-3787
>                 URL: https://issues.apache.org/jira/browse/HBASE-3787
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>    Affects Versions: 0.96.0, 0.94.4
>            Reporter: dhruba borthakur
>            Priority: Critical
>             Fix For: 0.96.0
>
>
> The HTable.increment() operation is non-idempotent. The client retries the increment RPC a few times (as specified by configuration) before throwing an error to the application. This makes it possible that the same increment call be applied twice at the server.
> For increment operations, is it better to use HConnectionManager.getRegionServerWithoutRetries()? Another  option would be to enhance the IPC module to make the RPC server correctly identify if the RPC is a retry attempt and handle accordingly.

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