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From "David Boreham" <da...@bozemanpass.com>
Subject Re: [replication] Master slave replication will not suffice
Date Thu, 24 Feb 2005 03:16:10 GMT
> Have any recommendations?  Advice?  How would you proceed to introduce 
> MMR into ApacheDS?

Hmm...I can only speak in generalities: some of the
techniques with which I'm most familar are patented...

For replication, you always need to store extra state
pertaining to the entries : change sequence numbers ,
or similar. Try to be careful about how this is stored,
otherwise you can end up with two databases that
you must maintain consistency (e.g. with 2-phase commit)
across. Ideally keep it all in the same database.

Be concerned about re-entrancy issues: an update
to the local server may originate with a client, or
with another replica, replaying its updates. Be sure
to distinguish between the two properly to avoid 
re-propagating the updates. 

Some updates will be due to conflict resolution,
not a direct replayed update. Much of the trickness
is to ensure that the conflict resolution mechanism
converges.

I have studied the Apache DS code, but right now
I'm not sure I can think of specific code-related
advice.

You need to pay very special attention to testing.



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