(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
