marco polo created ACCUMULO-3835:
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Summary: TabletServerBatchReaderIterator
Key: ACCUMULO-3835
URL: https://issues.apache.org/jira/browse/ACCUMULO-3835
Project: Accumulo
Issue Type: Bug
Components: client
Affects Versions: 1.6.2
Reporter: marco polo
When running many batch scanners in a JVM, we see a significant amount of cache
invalidation within the JVM when we prematurely close the batch scanner. When
we prematurely close the batch scanner ( and threads within it are running an
interrupt is sent to those threads, causing them to add the extents to the
failures map and invalidate the cache. This causes lock contention on the write
lock for the TabletLocatorImpl.
The lock contention hinders performance in a highly parallel client that does
not need to invalid the cache as a result of being stopped.
As a positive test to ensure this was my problem I added a conditional check to
the IOException handler in the run method of TabletServerBatchReaderIterator.
The conditional checked whether the query thread pool was shut down. If it was
not, we would invalidate the cache as we can assume the reason likely wasn't
interruption. If it was shut down, we would not invalide the cache. This
reduced lock contention dramatically and reduced runtime. This should cause no
harm as any other failure would cause cache invalidation through some other
route.
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