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https://issues.apache.org/jira/browse/ACCUMULO-4502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15637754#comment-15637754
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Josh Elser commented on ACCUMULO-4502:
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re impact -- http://brooker.co.za/blog/2012/09/10/volatile.html
tl;dr for a volatile variable under contention, read performance, with a high
variance, can be impacted by 25x and write perf by 100x. Heavily variant due to
multi-core and cache lines.
I'll see if I can find some time tonight or this weekend to dig into this code
myself since you made time to do the same, Ivan.
> Called next when there is no top
> --------------------------------
>
> Key: ACCUMULO-4502
> URL: https://issues.apache.org/jira/browse/ACCUMULO-4502
> Project: Accumulo
> Issue Type: Bug
> Components: core, tserver
> Affects Versions: 1.6.6
> Reporter: Ivan Bella
> Assignee: Ivan Bella
> Fix For: 1.7.3, 1.8.1, 2.0.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> This happens very rarely but we have seen the following exception (pulled
> from a server running 1.6.4). Looking at the code I believe this condition
> can still happen in 1.8.0:
> java.util.concurrent.ExecutionException: java.lang.IllegalStateException:
> Called next() when there is no top
> ...
> Caused by: java.lang.IllegalStateException: Called next() when there is no top
> HeapIterator.next(HeapIterator.java: 77)
> WrappingIterator.next(WrappingIterator.java: 96)
> MemKeyConversionIterator.next(InMemoryMap.java:162)
> SourceSwitchingIterator.readNext(SourceSwitchingIterator.java: 139)
> SourceSwitchingIterator.next(SourceSwitchingIterator.java: 123)
> PartialMutationSkippingIterator.consume(InMemoryMap.java:108)
> SkippingIterator.seek(SkippingIterator.java:43)
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