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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5974) Scanner retry behavior with RPC timeout on next() seems incorrect
Date Fri, 11 May 2012 19:14:49 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13273517#comment-13273517
] 

Todd Lipcon commented on HBASE-5974:
------------------------------------

bq. In the scenario Todd described, can the server keep the most recent batch of results so
that when server sees cookie from client carrying 1 less than expected value, the server can
resend the stored batch ?

I think it's too expensive in terms of memory consumption on the server. My assertion is that
this issue is very rare (or else people probably would have noticed the missing rows a lot
more often). So, keeping the last response batch cached server side seems a poor use of RAM.
                
> Scanner retry behavior with RPC timeout on next() seems incorrect
> -----------------------------------------------------------------
>
>                 Key: HBASE-5974
>                 URL: https://issues.apache.org/jira/browse/HBASE-5974
>             Project: HBase
>          Issue Type: Bug
>          Components: client, regionserver
>    Affects Versions: 0.90.7, 0.92.1, 0.94.0, 0.96.0
>            Reporter: Todd Lipcon
>            Priority: Critical
>
> I'm seeing the following behavior:
> - set RPC timeout to a short value
> - call next() for some batch of rows, big enough so the client times out before the result
is returned
> - the HConnectionManager stuff will retry the next() call to the same server. At this
point, one of two things can happen: 1) the previous next() call will still be processing,
in which case you get a LeaseException, because it was removed from the map during the processing,
or 2) the next() call will succeed but skip the prior batch of rows.

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