From: Anders Bengtsson <ndrsbngtssn@...>
Date: 2003-05-30T18:13:56+09:00
Subject: Re: Object Prevaylence vs. OODBMS or Madeleine vs. DyBase

 --- Brian Candler <B.Candler@pobox.com> wrote:
> > Madeleine itself doesn't have the concept of multiuser access or
> remote
> > clients, but if you for instance run one Madeleine "server" with a
> DRb
> > (Distributed Ruby) interface, then many DRb clients can work with
> it.
> 
> Beware: multiple DRb clients talking to the same remote object will
> make
> *multiple concurrent method calls* - each incoming request is handled
> as a
> separate thread on the same object at the server side.
> 
> Therefore DRb doesn't solve any concurrency issues you may have.

Since all "writes" to Madeleine have to go through the
execute_command() method, which is synchronized, this won't be a
problem.
 
> With Madeleine, I believe that serialising access to the database is
> your
> own responsibility - e.g. while reading a group of objects, you want
> to be
> sure that nothing is changing under your feet. But it's so fast that
> having
> a global mutex for database access isn't too big a penalty in many
> cases.

Yes, when reading you have to do your own synchronization if you need
it.
Maybe I should add a way to access Madeleine's big write lock from the
outside, if anyone wants to solve things the "global mutex" way.

/Anders



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Anders Bengtsson              ndrsbngtssn@yahoo.se
Stockholm, Sweden

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