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From Bart van der Schans <b.vandersch...@onehippo.com>
Subject Re: [jr3 microkernel] Write skew
Date Thu, 01 Dec 2011 15:33:06 GMT
On Thu, Dec 1, 2011 at 4:26 PM, Stefan Guggisberg
<stefan.guggisberg@gmail.com> wrote:
> On Thu, Dec 1, 2011 at 3:49 PM, Thomas Mueller <mueller@adobe.com> wrote:
>> Hi,
>>> A test-and-set operation necessarily requires at least some level of
>>> atomicity which can quickly become a bottleneck for a clustered setup.
>> Test-and-set is a problem in a clustered 'eventually consistent' model,
>> that's true. I don't know how test-and-set could be used in that way.
>> Possibly the easiest solution is that each node modification sets the node
>> type again (to the expected value) even if the user didn't change it.
>> But I don't think we should try to increase concurrency of write
>> operations within the *same* repository because that's not a problem at
>> all.
> i beg to differ ;)
> in jr2 saves are serialized. IMO that's a *real* problem, especially when
> saving large change sets. this problem can be addressed e.g. with an
> MVCC based model.

Yes, I agree. It's something I've seen many times in the field
(consider saving a large pdf in a cms). What makes the current
situation even worse is that you can't scale out the writes in a
cluster since all writes are serialized for the whole cluster. If you
could scale out and have concurrent writes on different cluster nodes
the problem would be much less worse.


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