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From Anthony Gardner <cyclewood_...@yahoo.co.uk>
Subject Re: DBI and threaded MPM
Date Wed, 11 Jul 2007 08:43:26 GMT
Perrin, I never received your mail (actually, I hardly receive any mails form this list) I
have to go to the archives to see if I've received any replies or to see what's been posted
in general!!

So, in answer to your questions ........


P. May I ask why you're using a threaded MPM?  Unless you're running on
   Windows, you should probably avoid it.  The threaded MPM uses a lot
   more memory than the prefork one.

A. This version of MP has just been installed and we have a dept. that deals
   with this sort of thing. It's not until we had a problem,
   that I started to look into versions of s/w etc. It's a big company
   and the admin dept. decide what to install. (I've since asked for the prefork mpm to be
installed)

P. (regarding using Thread::Sociable and threads::shared)
   They won't work because DBD modules carry around XS structures which
   don't know anything about perl threads.  That's the problem DBI::Pool 
   was trying to address.

A.  After I started looking into this issue, I quickly realised that  
     these wouldn't help me.

P.  Can you explain a little more about what the problem is and why you
     think it involves Apache::DBI?

A. We recently went live with a DB application and the system ground 
    to a halt. It could be due to many things, but the thing I'm looking at   
    is the fact that we had many network connections. I then found the
    info about  Databases and threaded MPM. From what I understand, 
    DB connections created at server startup are not shared amongst
    threads.

As I see now, threaded MPM doesn't sit well with DB and really, we shouldn't be using it at
all. I've made this clear to my admin dept. and we're going to install and test prefork MPM.


Thanks for getting back to me, anyway.

-Ants

Jonathan Vanasco <jvanasco@2xlp.com> wrote: 
On Jul 9, 2007, at 9:12 AM, Anthony Gardner wrote:

> http://perl.apache.org/docs/2.0/user/performance/ 
> mpm.html#Work_with_DataBases_under_Threaded_MPM
>
> I'm looking into a problem we're experiencing (lots of netword  
> connections) and I think the answer lies with Apache::DBI and the  
> version of mod_perl we're using.
>
> A few questions, does anyone know of the state of DBI::Pool?
>
> If anyone is using threaded MPM and Apache::DBI, how are they  
> dealing with sharing the the connection within the threads?
>
> I'm looking at Thread::Sociable (preference) and threads::shared and
>
> I'm looking for tips and/or defacto stds used at the time of writing.
> Any tips would be great while I continue playing with threads and  
> searching for other info.

Some people here ( not including me though ) are using connect_cached  
in DBI , and bypassing Apache::DBI altogether.  you might want to try  
that.
correct me if i'm wrong.. but i believe you want to not share dbi  
connections between threads.  wouldn't you need a factory class to  
toss you a fresh connect ?
if you want to do true connection pooling, you'd be best off with  
something like sqlrelay or pgpool.  the apache::dbi/dbi cached don't  
really pool; they just override connects for established connections  
on their process and reuse them.  things like sqlrelay/pgpool will  
let you use 50 db connections for 150 server processes ( by blocking  
a lot, yes )




// Jonathan Vanasco

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