-Re: Proposal: Remove explicit RowLocks in 0.96
Andrew Purtell 2012-12-11, 22:40
I would add another point to the reasoning:
5) Users can build application level rowlocks using HBase's CAS primitives,
or ZooKeeper / Curator recipes (since ZooKeeper is always available in
HBase environments), and these don't suffer the problems mentioned.
On Tue, Dec 11, 2012 at 2:37 PM, Andrew Purtell <[EMAIL PROTECTED]> wrote:
> I agree with all points. +1
> On Tue, Dec 11, 2012 at 2:00 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
>> Including user mailing list.
>> On Tue, Dec 11, 2012 at 1:52 PM, Gregory Chanan <[EMAIL PROTECTED]
>> > 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
>> > 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
>> > the RowLocks or by starving other non-contending row operations by
>> > occupying server handlers stuck waiting to acquire the locks.
>> > Thoughts?
>> > Greg
> Best regards,
> - Andy
> Problems worthy of attack prove their worth by hitting back. - Piet Hein
> (via Tom White)
Problems worthy of attack prove their worth by hitting back. - Piet Hein
(via Tom White)