Re: CDBI and mod_perl

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Matt S Trout wrote:
> I sincerely doubt you'll find this to be the case; an idling database
> connection shouldn't require noticeable amounts of resources. For example,
> MySQL AFAIK only maintains a small buffer per connection plus some tracking
> info and everything else is shared.

I would recommend you read Jeremy Zawodny's "High Performance MySQL" for 
examples of times when it really matters how many connections to the 
database you have.  He has stories about shutting down persistence on 
connections for this reason.  I don't need to handle as much traffic as 
Yahoo does, but I don't have as many servers as Yahoo does either.

It's fairly common to make MySQL's per-connection buffers significantly 
higher when dealing with a large database, in order to improve query 
performance.  At that point, every idle connection means less memory 
available for the shared buffers.  I have personally experienced this 
problem.  When dealing with something like Oracle, you may actually have 
licensing problems from too many connections, or hit the wall on how 
many your big-iron server can support.  Oracle connections are 
resource-intensive.

If you poll your neighborhood DBAs, I suspect they will agree that 
doubling the number of idle connections to a server can be a serious 
problem in many situations.

- Perrin