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HBase >> mail # user >> Differences between ScannerTimeoutException and LeaseException during a scanner

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Re: Differences between ScannerTimeoutException and LeaseException during a scanner
It looks like a "race condition" between the check that the lease is
expired in HRegionServer.next, and the LeaseListener.leaseExpired methods.
If the next call from the client is done before the lease listener do its
job, the scanner still exists in the map but is expired, which causes
LeaseException instead of UnknownScannerException.
Indeed I found this in the logs:

2012-11-15 08:45:34,003 ERROR
org.apache.hadoop.hbase.regionserver.LeaseException: lease
'4939065839430667309' does not exist
 at org.apache.hadoop.hbase.regionserver.Leases.removeLease(Leases.java:231)
 at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Method.java:597)


2012-11-15 08:48:37,734 INFO
org.apache.hadoop.hbase.regionserver.HRegionServer: Scanner
4939065839430667309 lease expired

The scanner is properly closed way too late!
I just realized there is already a related issue about this:

2012/11/15 Guillaume Perrot <[EMAIL PROTECTED]>

> Hi,
> Similar questions have been mailed in the past, but they are not clear
> enough to me, so here is a new one:
> In HBase 0.90.3, when a client scanner was too slow to advance (no actual
> next call within 60s), we had a nice ScannerTimeoutException in client
> (UnknownScannerException in region server).
> With HBase 0.92.1, when I simulate such a slow scanner I still have this
> exception.
> But in our production environment, scanners that used to
> produce ScannerTimeoutException in HBase 0.90.3 no longer produce them
> since we upgraded to HBase 0.92.1.
> Instead we now have:
> org.apache.hadoop.hbase.regionserver.LeaseException:
> org.apache.hadoop.hbase.regionserver.LeaseException: lease
> '2770824890045864909' does not exist
> at org.apache.hadoop.hbase.regionserver.Leases.removeLease(Leases.java:231)
>  at
> org.apache.hadoop.hbase.regionserver.HRegionServer.next(HRegionServer.java:2117)
> at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
>  at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
>  at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:364)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1326)
> I don't uderstand the workflow leading to this exception instead of a
> ScannerTimeoutException, any local attempt to reproduce this problem leads
> to a ScannerTimeoutException and not a LeaseException.
> Any idea ?
> Thanks in advance.

  *Guillaume Perrot
**Software Engineer
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