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From "Will Glass-Husain" <wgl...@forio.com>
Subject Re: duplicate ID exception in cluster
Date Tue, 05 Dec 2006 22:42:42 GMT
Hi Henning!

It's a real (Tomcat) cluster.  Two instances of Tomcat talking to a
single database.  (no database replication).  I use Apache/mod_jk to
split requests (based on session) between the two Tomcats.  Allows me
to run high number of users with a memory-heavy application.

Thought briefly about database replication but since this is
write-heavy application it didn't seem to make sense.

thanks,
WILL

On 12/5/06, Henning P. Schmiedehausen <hps@intermeta.de> wrote:
> "Will Glass-Husain" <wglass@forio.com> writes:
>
> >Hi,
>
> >I just set up a new 2 server cluster with two instances of Tomcat both
> >reading/writing from a single database.  I'm using Torque 3.0, the
> >default ID Broker and MySQL 5. (InnoDB)
>
> Real cluster or just master/slave (or master/master with only one master
> active at a time)? The latter is just replication, not a real cluster.
>
> >My problem... Under heavy load, I notice that most write requests on
> >one of the servers fails with a duplicate ID error.  Typically, each
> >page request that fails does 10-20 insert statements.
>
> >Any tips as to how I might make this cluster work with simultaneous writes?
>
> a) in a master/master config, you can not write to both masters at the
>    same time. End of story. I had a summer project where we tested
>    exactly that *very* extensively. It does not work. No matter what you
>    google on the internet or what mysql.com wants to tell you. You will
>    get the described error sooner or later. If you want to have
>    master/master with failover, that is fine. Two active masters not.
>
> b) you probably run into the AUTO_INCREMENT problem. Make sure that you
>    have 5.0.20 at least. See http://dev.mysql.com/doc/refman/5.0/en/replication-features.html
>    for some docs.
>
>
>         Best regards
>                 Henning
>
> --
> Henning P. Schmiedehausen  -- hps@intermeta.de | J2EE, Linux,
> 91054 Buckenhof, Germany   -- +49 9131 506540 | Apache person
> Open Source Consulting, Development, Design | Velocity - Turbine guy
>
>           "Save the cheerleader. Save the world."
>
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>


-- 
Forio Business Simulations

Will Glass-Husain
wglass@forio.com
www.forio.com

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