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From Borut BolĨina <>
Subject Re: Database replication and caching
Date Mon, 31 Jul 2006 16:40:56 GMT
Oh, I forgot to mention that PK generation will be completely handled 
outside Cayenne, so PK (oid) will be just another db attribute. It is 
guaranteed, that insert will be done with different PKs at each 
concurrent running applications.

Gentry, Michael (Contractor) pravi:
> I'm not familiar with PostgreSQL's replication capabilities, but I'd be
> concerned about primary key duplication and possible data loss (this
> would be outside of Cayenne's control).  For example, what would happen
> if both applications ran the sequence to generate PKs at the same time?
> -----Original Message-----
> From: Borut Bolcina [] 
> Sent: Monday, July 31, 2006 11:52 AM
> To: cayenne-user
> Subject: Database replication and caching
> Hello,
> I need an advice on using Cayenne in an environment where two PostgeSQL
> databases are configured to replicate from each other for failover 
> capability. I am thinking of two Cayenne enabled applications (load 
> distribution) which insert records in one of those two databases. 
> Application one (A1) inserts in database one (DB1) and application two 
> (A2) inserts in database two (DB2).
> The insertion, deletion or update will cause Java triggers in PostgreSQL
> to call appropriate Java method in the application. If for any reason 
> one of the databases is down for some time, the replication mechanism 
> will bring the second database up-to date which will trigger invocations
> of the Java methods, so the second application will be in the correct 
> state also.
> As long as triggers do not modify records, everything should be ok with 
> Cayenne. In case, which I don't foresee now, the records will be 
> modified on database level, all DataContexts should be invalidated, am I
> right?
> Is there any other (caching) problem you see in this architecture?
> Regards,
> Borut

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