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HBase >> mail # dev >> Providing coprocessor hooks in rollbackMemStore while doing puts

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RE: Providing coprocessor hooks in rollbackMemStore while doing puts
What about providing more hooks with the batch put operation? A pre and post hooks for the entire batch operation. Before startRegionOperation() and after the closeRegionOperation()? [ In  put(Pair<Put,Integer>[] putsAndLocks)  ]
Also one more issue regarding the hooks at the miniBatchPut
During this doMiniBatchPut, the prePut () will be called for each and every Put in the list one after the other.  Later in doMiniBatchPut when it tries to acquire the rowlocks, it will try to get atleast one lock. For those rows it is able to acquire locks, those Puts only will happen. Then the loop in the method, put(Pair<Put,Integer>[] putsAndLocks) will call doMiniBatchPut again.  During this time also we will call prePut() for every puts in the original puts list. The pre hook is called for all rows not even checking whether the lock for the same is available or not. As per the comments in the prePut() call it is called outside the lock to avoid the possible deadlocks.  But calling the prePut() more times for same Put, will it be an issue? If kernel is not handling this, may be the CP need to handle this.... Any comments?

As per the code in the HRegion. put() -> The prePut is called after acquiring the rowlock.

Thanks & Regards

From: Andrew Purtell [[EMAIL PROTECTED]]
Sent: Friday, March 23, 2012 2:14 AM
Subject: Re: Providing coprocessor hooks in rollbackMemStore while doing puts


Best regards,

    - Andy
On Mar 22, 2012, at 9:24 AM, lars hofhansl <[EMAIL PROTECTED]> wrote:

> +1
> That seems like a hole in the coprocessor framework that we missed when we did added the rollback logic.
> ________________________________
> From: Ramkrishna.S.Vasudevan <[EMAIL PROTECTED]>
> Cc: 'rama krishna' <[EMAIL PROTECTED]>
> Sent: Thursday, March 22, 2012 7:59 AM
> Subject: Providing coprocessor hooks in rollbackMemStore while doing puts
> With coprocessors hooks while put happens we have the provision to create
> new puts to other tables or regions.  These puts can be done with writeToWal
> as false.
> In 0.94 and above the puts are first written to memstore and then to WAL.
> If any failure in the WAL append or sync the memstore is rollbacked.
> Now the problem is that if the put that happens in the main flow fails there
> is no way to rollback the
> puts that happened in the prePut.
> Can we add hooks like preRollbackMemstore and postRollBackMemstore so that I
> will be atleast able to rollback the entries?
> Can we raise a JIRA for solving this.