This could be HBASE-2077 J-D
On Wed, Apr 13, 2011 at 9:15 AM, Gary Helmling <[email protected]> wrote: > Hi Vidhya, > > So it sounds like the timeout thread is timing out the scanner when it takes > more than 60 seconds reading through the large column family store file > without returning anything to the client? Even without the TTL expiration > being applied, I think I've heard of this in other cases where a very > restrictive filter was used on a large table scan. > > If this is the case, it certainly seems like we should handle it better. We > could do something as simple as refreshing the scanner timestamp every X > rows when iterating server side. > > I'll check the code and open a JIRA (if we don't have one existing). Thanks > for detailing the problem. > > --gh > > > > On Wed, Apr 13, 2011 at 7:44 AM, Vidhyashankar Venkataraman < > [email protected]> wrote: > >> Hi >> We had enabled scanner caching but I don't think it is the same issue >> because scanner.next in this case is blocking: the scanner is busy in the >> region server but hasn't returned anything yet since a row to be returned >> hasn't been found yet (all rows have expired but are still there since they >> havent been compacted yet). >> >> Vidhya >> >> On 4/13/11 1:44 AM, "Ted Yu" <[email protected]> wrote: >> >> Have you read the following thread ? >> "ScannerTimeoutException when a scan enables caching, no exception when it >> doesn't"Did you enable caching ? If not, it is different issue. >> >> On Wed, Apr 13, 2011 at 12:40 AM, Vidhyashankar Venkataraman < >> [email protected]> wrote: >> >> > (This could be a known issue. Please let me know if it is). >> > >> > We had a set of uncompacted store files in a region. One of the column >> > families had a store file of 5 Gigs. The other column families were >> pretty >> > small (a few megabytes at most). >> > >> > It so turned out that all these files had rows whose TTL had expired. >> Now >> > when this region was scanned (which should yield a result of a null set), >> we >> > got Scanner timeouts and UnknownScannerExceptions. >> > >> > And when we tried scanning the region without the large column family, >> the >> > scanner returned back safely with no result. >> > >> > So, I major compacted it and the scan started working correctly. >> > >> > So it looks like timeouts happen if the scanner does not return any >> output >> > for a specified time. >> > Which isn't exactly the correct thing to do, because it could be the case >> > that the scanner was indeed busy but it just so happened that there are >> no >> > rows yet to return back to the client. >> > >> > We can try increasing the scanner timeout, but this doesn't resolve the >> > underlying problem. Is this a know issue? >> > >> > Thank you >> > Vidhya >> > >> >> >
