On Thursday 20 November 2003 7:15 pm, Matthew Smith wrote:
> > From: "Ken Burcham" <[EMAIL PROTECTED]>
> >
> >  can I do that lookup just once
> > and stuff it somewhere like an application server variable?
>
> I use Apache::AxKit::Plugin::Session, there is a 'Global' taglib that
> let's you share data between all instances of apache.  It's a bit
> involved though, if you're not doing access and authentication it might
> be easier to directly use Apache::Session, there is a shared memory
> module which would do the job.  Maybe others have recomendations on the
> best way to access shared memory for mod_perl.

The problem is that you have to have a backing store for your session data, 
which usually is an SQL database itself... Thus you would be caching your 
objects in a database, so why bother? I believe there is an implementation of 
an Apache::Session storage module that uses shared memory, but remember that 
shared memory is NOT without a cost! In fact in my testing I discovered that 
for most applications overall performance is best when you just let the 
objects live in MySQL. Remember, MySQL has a pretty good query cache, so in 
effect the database server is doing the caching, and if you think about it if 
you can afford to dedicate the memory to a cache, it doesn't matter which 
application does the caching. The only downside is the cost of 
serialization/deserialization and moving the data around.
>
>  > where does this cache
> >
> > live?  Or does it?
>
> My understanding is that it is stored in the memory of the perl instance
> that is running.  I also understand that there is a perl instance for
> each apache server instance running - so things can get out of sync if
> your browser comes in on a different server - hence the need for a
> shared memory storage.
>
> matt
>
>
>
>
>
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-- 
Tod Harter
Giant Electronic Brain
http://www.giantelectronicbrain.com


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