[jira] [Updated] (HBASE-8877) Reentrant row locks

["Dave Latham (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-8877?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dave Latham updated HBASE-8877:
-------------------------------

    Attachment: HBASE-8877.patch

Here's a patch implementing reentrant row locks.  It changes the locking interface to these 3 methods:
 - void getRowLock(byte[] row) throws IOException (acquire, throw if unable to acqurie before timeout)
 - boolean tryRowLock(byte[] row) (acquire without wait and return true iff successful)
 - void releaseMyRowLocks() (release all row locks held by the current thread)


                
> Reentrant row locks
> -------------------
>
>                 Key: HBASE-8877
>                 URL: https://issues.apache.org/jira/browse/HBASE-8877
>             Project: HBase
>          Issue Type: Bug
>          Components: Coprocessors, regionserver
>            Reporter: Dave Latham
>            Assignee: Dave Latham
>             Fix For: 0.95.2
>
>         Attachments: HBASE-8877.patch
>
>
> HBASE-8806 revealed performance problems with batch mutations failing to reacquire the same row locks.  It looks like HBASE-8806 will use a less intrusive change for 0.94 to have batch mutations track their own row locks and not attempt to reacquire them.  Another approach will be to support reentrant row locks directly.  This allows simplifying a great deal of calling code to no longer track and pass around lock ids.
> One affect this change will have is changing the RegionObserver coprocessor's methods preBatchMutate and postBatchMutate from taking a {{MiniBatchOperationInProgress<Pair<Mutation, Integer>> miniBatchOp}} to taking a {{MiniBatchOperationInProgress<Mutation> miniBatchOp}}.  I don't believe CPs should be relying on these lock ids, but that's a potential incompatibility.

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