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From "Geoff Hendrey" <ghend...@decarta.com>
Subject RE: ScannerTimeoutException
Date Thu, 08 Sep 2011 15:23:44 GMT
Hi Jan -

The relevant code looks like this. I added addFamily. Still getting the ScannerTimeoutException.
Arghhh. This is really becoming a mission critical problem for my team...Furthermore, the
problem becomes more and more frequent, to the point that the job almost never finishes. At
the beginning of the job, the timout never happens. By the end, it's happening 9 out of 10
attempts...

                Scan scan = new Scan(Bytes.toBytes(key));
                scan.setCaching(1);
                scan.setMaxVersions(1);
                scan.addFamily(Bytes.toBytes("V1")); 
                scan.addColumn(Bytes.toBytes("V1"), Bytes.toBytes("cluster_map"));
                scan.addColumn(Bytes.toBytes("V1"), Bytes.toBytes("version_control_number"));

-geoff

-----Original Message-----
From: Geoff Hendrey 
Sent: Tuesday, September 06, 2011 9:51 AM
To: Jan Lukavsk√Ĺ; user@hbase.apache.org
Cc: hbase-user@hadoop.apache.org
Subject: RE: ScannerTimeoutException

I'll try your suggestions!

-----Original Message-----
From: Jan Lukavsk√Ĺ [mailto:jan.lukavsky@firma.seznam.cz] 
Sent: Tuesday, September 06, 2011 9:48 AM
To: user@hbase.apache.org
Cc: Geoff Hendrey; hbase-user@hadoop.apache.org
Subject: Re: ScannerTimeoutException

Hi Geoff,

we are having these issues when the scanner uses scan.addColumn() and 
the column is sparse, in the sense there are many rows with some other 
column in the same column family. I suppose your problems will vanish if 
you use scan.addFamily() call instead. The same behavior may appear if 
you are reading from region after massive delete (then the timeouts 
settle down after major compation), or when using server side Filters.

Changing scan.addColumn() to scan.addFamily() brings some overhead, 
which I think could be removed by RegionServer renewing the lease of 
scanner while reading data, not only after first entry to 
HRegionServer.next().

Would this be worth opening a JIRA?

Jan

On 6.9.2011 04:11, Geoff Hendrey wrote:
> Hi -
>
>
>
> I found some odd behavior with ResultScanner.next(). Usually the times
> for next() are couple hundred ms. But occasionally the call to next
> spikes VERY long. In fact, I have the timeout set to 60 seconds (60000),
> but once in a while the call to next() itself is interrupted by the
> ScannerTimeoutException after more than 60 seconds. It seems odd that
> the call to next itself can be interrupted because "61107ms passed since
> the last invocation, timeout is currently set to 60000"
>
> The only thing I can think of is that a GC kicks in after the call to
> next begins, but before the call returns, and the server is still
> ticking the timeout. But this seems to happen periodically with
> regularity. The odds of the GC kicking in at that exact instant, so
> often, seem kind of low.
>
> -geoff
>
>
>


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