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HBase >> mail # dev >> Proposal: Remove explicit RowLocks in 0.96


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Gregory Chanan 2012-12-11, 21:52
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Re: Proposal: Remove explicit RowLocks in 0.96
Including user mailing list.

On Tue, Dec 11, 2012 at 1:52 PM, Gregory Chanan <[EMAIL PROTECTED]>wrote:

> Over in HBASE-7263 there has been some discussion about removing support
> for explicit RowLocks in 0.96.  This would involve the following:
> - Remove lockRow/unlockRow functions in HTable and similar
> - Remove constructors for Put/Delete/Increment/Get that take RowLocks
> - functions in HRegion no longer take lockIds (checkAndPut, append,
> increment, etc).  This would affect coprocessors that call directly into
> those functions.
>
> I have a patch in HBASE-7315 with the details.
>
> This would violate our usual rule of deprecating a feature one release
> before removing.  The reasoning is as follows:
> 1) RowLocks are broken
>  They are only kept in the memory associated with the region, so on a
> split, region move, RS crash, they just disappear
>
> 2) 0.96 is special
> Now seems like a good time to clean things up since we've made some
> incompatible changes already (e.g. protobufing) and we could have a cleaner
> client implementation
>
> 3) RowLocks have been deprecated "in spirit" for awhile
> Here's a post from 2009 cautioning against their use:
> http://bb10.com/java-hadoop-hbase-user/2009-09/msg00239.html
> and a more recent example:
> http://permalink.gmane.org/gmane.comp.java.hadoop.hbase.user/23488
>
> 4) RowLocks are hard to use effectively
> Clients can deadlock or starve themselves, either by forgetting to release
> the RowLocks or by starving other non-contending row operations by
> occupying server handlers stuck waiting to acquire the locks.
>
> Thoughts?
>
> Greg
>
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Andrew Purtell 2012-12-11, 22:37
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Andrew Purtell 2012-12-11, 22:40
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Jonathan Hsieh 2012-12-11, 22:50
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lars hofhansl 2012-12-11, 23:19
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Stack 2012-12-12, 07:08
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Gregory Chanan 2012-12-13, 00:31