[mod_python] module caching problem

1) build your apache server with mpm_worker (./configure 
-with-mpm=worker)  (this only works with Apache 2.x)

2) in httpd.conf  (all values of "150" in this example should be set to 
the max number of concurrent requests)

ThreadLimit 150
ServerLimit 1
StartServers 1
MaxClients 150
MinSpareThreads 1
MaxSpareThreads 150
ThreadsPerChild 150
MaxRequestsPerChild 0

I have not tested this a whole bunch, but it should work, according to 
http://httpd.apache.org/docs-2.0/mod/worker.html

I'm also not sure of the knock-on effects on performance of doing this.  
YMMV.  If anyone knows of a good reason *not* to do this, please speak up.

-Chris

P.S.  Even in prefork mode, if an apache process needs a module that has 
already been loaded into memory *by that process*, it will be re-used 
and not reloaded.

Huzaifa Tapal wrote:

>Yes I am using linux on a debian OS.  How can I configure apache to not run
>with mpm_prefork?  Pretty much I want to use Shared Memory with mod_python
>so that for simultaneous requests it uses any modules that are already
>loaded in memory rather than instantiating new processes.
>
>Any ideas?
>
>Hozi  
>
>-----Original Message-----
>From: mod_python-bounces at modpython.org
>[mailto:mod_python-bounces at modpython.org] On Behalf Of Damjan
>Sent: Tuesday, November 23, 2004 6:49 PM
>To: mod_python at modpython.org
>Subject: Re: [mod_python] module caching problem
>
>  
>
>>I am running into a problem with mod_python in that, I am importing a
>>    
>>
>module
>  
>
>>in the handler which creates a singleton in memory.  I am using the module
>>to hold cache information for any other modules that import the same
>>    
>>
>module.
>  
>
>>I started testing the cache mechanism when I noticed that the module was
>>being imported multiple times and not just once after the first request
>>after apache had started.  To test this, I put a few lines of code in the
>>module to write to a file the time it was last imported.  I noticed that
>>after restarting apache, the first time it writes to the file.  If I hit
>>refresh on my page immediately, multiple times, it doesn't write.  If I
>>    
>>
>wait
>  
>
>>like 10 seconds or more and then hit refresh again, it reimports that
>>    
>>
>module
>  
>
>>that should have been cached.
>>
>>Also, If I make a request for a page from two different clients, it
>>reimports the module from each client.  Am I mistaken in thinking that any
>>module imported in the handler then is cached in mod_python's module cache
>>and subsequent imports of that module then are simply served up from the
>>cache.  Under what conditions then would the same module get reimported if
>>no modifications were made to that module?
>>    
>>
>
>I guess your are runnig Apache with mpm_prefork? 
>In that case there's a completely different python interpreter for each
>Apache process, so your caching module is loaded in each of them.
>
>Your testing showed how apache processes get to serve requests, if it gets
>two simultaneus requests two apache processes will be active, each
>serving one of the request. But if you only generate one request after
>another, its most likely that the same process will serve  both
>requests... of course this depends on OS implementation... I think you
>are running on Linux, no?
>
>  
>