Thiruvel Thirumoolan created HBASE-19468:
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Summary: FNFE during scans and flushes
Key: HBASE-19468
URL: https://issues.apache.org/jira/browse/HBASE-19468
Project: HBase
Issue Type: Sub-task
Affects Versions: 1.3.1
Reporter: Thiruvel Thirumoolan
Priority: Minor
We see FNFE exceptions on our 1.3 clusters when scans and flushes happen at the
same time. This causes regionserver to throw a UnknownScannerException and
client retries.
This happens during the following sequence:
1. Scanner open, client fetched some rows from regionserver and working on it
2. Flush happens and storeScanner is updated with flushed files
(StoreScanner.updateReaders())
3. Compaction discharger runs and cleans up the newly flushed file as we don't
have new scanners on it yet.
4. Client issues scan.next and during StoreScanner.resetScannerStack(), we get
a FNFE. RegionServer throws a UnknownScannerThe client retries in 1.3. With
branch-1.4, the scan fails with a DoNotRetryIOException.
[~ram_krish], My proposal is to increment the reader count during
updateReaders() and decrement it during resetScannerStack(), so discharger
doesn't clean it up. Scan lease expiries also have to be taken care of. Am I
missing anything? Is there a better approach?
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