[jira] [Commented] (HBASE-4557) Do something better than UnknownScannerException

["Ted Yu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479375#comment-13479375 ] 

Ted Yu commented on HBASE-4557:
-------------------------------

One a related note:
It is difficult for user to find out the correlation between region name and scanner name when they see:
{code}
Caused by: org.apache.hadoop.hbase.UnknownScannerException: org.apache.hadoop.hbase.UnknownScannerException: Name: -3944363018500584369
	at org.apache.hadoop.hbase.regionserver.HRegionServer.next(HRegionServer.java:1869)
{code}
When entry keyed by scannerName is removed from scanners map, can we temporarily store (scanner name, region name) mapping so that the above exception message can provide more information to the user ?
                
> Do something better than UnknownScannerException
> ------------------------------------------------
>
>                 Key: HBASE-4557
>                 URL: https://issues.apache.org/jira/browse/HBASE-4557
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.90.4
>            Reporter: Jean-Daniel Cryans
>             Fix For: 0.96.0
>
>
> UnknownScannerException is a plague, there's no reason we should not at least try to create a new scanner. If that fails again, maybe try automatically setting a lower scanner caching (if possible and with proper loggin) and retry again.

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