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https://issues.apache.org/jira/browse/HBASE-10205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13853372#comment-13853372
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Arjen Roodselaar commented on HBASE-10205:
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I took the Chunhui's patch, but made some additional changes to allow
parallelism in the BucketAllocator on the BucketSizeInfo level. I think
synchronization can be removed from BucketAllocator.allocateBlock() and
BucketAllocator.freeBlock(), but need to verify this under some stress. I will
be running a load test over the next 24 hours and report back.
> ConcurrentModificationException in BucketAllocator
> --------------------------------------------------
>
> Key: HBASE-10205
> URL: https://issues.apache.org/jira/browse/HBASE-10205
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.89-fb
> Reporter: Arjen Roodselaar
> Assignee: Arjen Roodselaar
> Priority: Minor
> Fix For: 0.89-fb, 0.99.0
>
> Attachments: hbase-10205-trunk.patch
>
>
> The BucketCache WriterThread calls BucketCache.freeSpace() upon draining the
> RAM queue containing entries to be cached. freeSpace() in turn calls
> BucketSizeInfo.statistics() through BucketAllocator.getIndexStatistics(),
> which iterates over 'bucketList'. At the same time another WriterThread might
> call BucketAllocator.allocateBlock(), which may call
> BucketSizeInfo.allocateBlock(), add a bucket to 'bucketList' and consequently
> cause a ConcurrentModificationException. Calls to
> BucketAllocator.allocateBlock() are synchronized, but calls to
> BucketAllocator.getIndexStatistics() are not, which allows this race to occur.
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