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From Berin Loritsch <>
Subject Re: connection pool fail over
Date Wed, 29 Jun 2005 20:03:11 GMT
Rui Alberto wrote:
> Hi,
> I have three replicated databases and a connection pool to each database
> instance. 
> The network to database instances is a little unstable, so I want to
> check at least one connection in the pool before passing pool identifier
> to SQLTransformer. If connection is broken, I wanna try next other pool.
> Does anyone know if there's a simple way to handle this situation?
> Should I write a selector, or an input module maybe or an action?! 
> Writing a selector or action implies an exhaustive sitemap! :|
> Any idea?

Commercial database driver vendors include such a feature.  Both 
DataDirect (produce enhanced drivers for SQLServer, Oracle, Informix, 
and others) and JNetDirect (produce enhanced drivers for SQLServer) have 
round-robin database failover.  Essentially as soon as the 
javax.sql.DataSource they have determines a pooled connection has gone 
bad, it will create a connection from the next database in the list.

You would just need to use the J2EEDataSource component in Cocoon to 
connect to it.

There is a caveat with the commercial database driver vendors: price. 
If you are using BEA WebLogic or IBM WebSphere, you are already using 
the latest DataDirect drivers and that is built into the price of the 

We opted for JNetDirect on our current project because for reasons 
beyond us we had to work with SQLServer.  The drivers from Microsoft are 
4 years old and they have no intention of updating them.

Design is a funny word. Some people think design means how it looks.
But of course, if you dig deeper, it's really how it works.

                                                        -- Steve Jobs

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