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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:
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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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