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From "Sean Sechrist (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3686) Scanner timeout on RegionServer but Client won't know what happened
Date Wed, 23 Mar 2011 15:16:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010169#comment-13010169
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Sean Sechrist commented on HBASE-3686:
--------------------------------------

It was an old customization that had been reverted on the server but not in the client's config.


It would be hard to return a better message in the UnknownScannerException, because the region
server doesn't know whether it was a scanner whose lease expired or if it is a genuine unknown
scanner.

So, I think the scan telling the server the lease period does seem like the best bet.

> Scanner timeout on RegionServer but Client won't know what happened
> -------------------------------------------------------------------
>
>                 Key: HBASE-3686
>                 URL: https://issues.apache.org/jira/browse/HBASE-3686
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.89.20100924
>            Reporter: Sean Sechrist
>            Priority: Minor
>
> This can cause rows to be lost from a scan.
> See this thread where the issue was brought up: http://search-hadoop.com/m/xITBQ136xGJ1
> If hbase.regionserver.lease.period is higher on the client than the server we can get
this series of events: 
> 1. Client is scanning along happily, and does something slow.
> 2. Scanner times out on region server
> 3. Client calls HTable.ClientScanner.next()
> 4. The region server throws an UnknownScannerException
> 5. Client catches exception and sees that it's not longer then it's hbase.regionserver.lease.period
config, so it doesn't throw a ScannerTimeoutException. Instead, it treats it like a NSRE.
> Right now the workaround is to make sure the configs are consistent. 
> A possible fix would be to use whatever the region server's scanner timeout is, rather
than the local one.

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