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https://issues.apache.org/jira/browse/HBASE-11126?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ramkrishna.s.vasudevan updated HBASE-11126:
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Status: Patch Available (was: Open)
Adds a set of new hooks for
Append, Increment, checkAndPut and checkAndDelete.
that operates after getting the row lock and the mvcc has completed so that any
CP operation that happens will have the updated view.
Also adds another hook in before preparingDeleteTimeStamps. (only a prehook).
This is because it will be needed in Visibility deletes use case where the
deleteColumn with latest version would be needed to be updated with the actual
latest timestamp based on matching visibility expression.
Internally we had a discussion to pass the RowLock also to the new hooks as
param. But later thought even if needed could be passed to the Context object
and doing that way could avoid any BC related issue.
> Add RegionObserver pre hooks that operate under row lock
> --------------------------------------------------------
>
> Key: HBASE-11126
> URL: https://issues.apache.org/jira/browse/HBASE-11126
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 0.99.0, 0.98.3
> Reporter: Andrew Purtell
> Assignee: ramkrishna.s.vasudevan
> Attachments: HBASE-11126_1.patch
>
>
> The coprocessor hooks were placed outside of row locks. This was meant to
> sidestep performance issues arising from significant work done within hook
> invocations. However as the security code increases in sophistication we are
> now running into concurrency issues trying to use them as a result of that
> early decision. Since the initial introduction of coprocessor upcalls there
> has been some significant refactoring done around them and concurrency
> control in core has become more complex. This is potentially an issue for
> many coprocessor users.
> We should do either:\\
> - Move all existing RegionObserver pre* hooks to execute under row lock.
> - Introduce a new set of RegionObserver pre* hooks that execute under row
> lock, named to indicate such.
> The second option is less likely to lead to surprises.
> All RegionObserver hook Javadoc should be updated with advice to the
> coprocessor implementor not to take their own row locks in the hook. If the
> current thread happens to already have a row lock and they try to take a lock
> on another row, there is a deadlock risk.
> As always a drawback of adding hooks is the potential for performance impact.
> We should benchmark the impact and decide if the second option above is a
> viable choice or if the first option is required.
> Finally, we should introduce a higher level interface for managing the
> registration of 'user' code for execution from the low level hooks. I filed
> HBASE-11125 to discuss this further.
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