Amitanand Aiyer created HBASE-8942:
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Summary: DFS errors during a read operation (get/scan), may cause
write outliers
Key: HBASE-8942
URL: https://issues.apache.org/jira/browse/HBASE-8942
Project: HBase
Issue Type: Bug
Affects Versions: 0.89-fb, 0.95.2
Reporter: Amitanand Aiyer
Assignee: Amitanand Aiyer
Priority: Minor
This is a similar issue as discussed in HBASE-8228
1) A scanner holds the Store.ReadLock() while opening the store files ...
encounters errors. Thus, takes a long time to finish.
2) A flush is completed, in the mean while. It needs the write lock to
commit(), and update scanners. Hence ends up waiting.
3+) All Puts (and also Gets) to the CF, which will need a read lock, will have
to wait for 1) and 2) to complete. Thus blocking updates to the system for the
DFS timeout.
Fix:
Open Store files outside the read lock. getScanners() already tries to do this
optimisation. However, Store.getScanner() which calls this functions through
the StoreScanner constructor, redundantly tries to grab the readLock. Causing
the readLock to be held while the storeFiles are being opened, and seeked.
We should get rid of the readLock() in Store.getScanner(). This is not
required. The constructor for StoreScanner calls getScanners(xxx, xxx, xxx).
This has the required locking already.
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