[mod_python] VirtualDocumentRoot, PythonPath and Subinterpreters

On 31/01/2006, at 6:36 PM, Troy Kruthoff wrote:

> How does one go about getting mod_python to know the DocumentRoot when
> using the apache VirtualDocumentRoot directive?  Below is a my vhost
> conf showing what I am trying to accomplish (I'm trying to get the
> PythonPath to match the VirtualDocumentRoot:
>
> <VirtualHost *:80>
>     ServerAdmin webmas... at dummy-host.example.com
>     UseCanonicalName Off
>     VirtualDocumentRoot /www/vhosts/%0
>
>     DirectoryIndex index.py
>     PythonPath "sys.path+['/www/vhosts/%0']"
>     AddHandler mod_python .py
>     PythonHandler index
>     PythonDebug On
>     ServerName *.example.com
>     ErrorLog logs/dummy-host.example.com-error_log
>     CustomLog logs/dummy-host.example.com-access_log common
> </VirtualHost>

I'll have to read properly what you are writing about and think about  
it,
but not sure there is a real clean way in current mod_python versions
of handling this. There has been requests for something that would
allow wildcarding on PythonPath previously, see:

   https://issues.apache.org/jira/browse/MODPYTHON-63

but I don't believe the suggested changes were practical given current
issues with the module importing system.

It is possible that with changes I will be proposing to the module  
importing
system and how updates to PythonPath are managed and/or avoided,
that this may be more practical to do.

> This type of setup makes it viable to run thousands of vhosts from a
> single httpd.conf file, and allows the addition and deletion of vhosts
> without restarting apache.  This brings me to another point.  If we
> are planning to use the worker MPM, a sub-interpreter will be created
> for each vhost.  I'm assuming if we can get VirtualDocumentRoot to
> work, that the same will apply.  Does anyone know:
>
> 1)  How many sub-interpreters is too much?

Good question. Anyone got an answer to this based on actual usage?
I would image that more than a small number may blow out process
sizes too much.

> 2)  Is there a way to monitor sub-interpreters and kill stale ones?

No. Only way is to do an "apachectl graceful" restart to kill off child
processes and start new ones to replace them.

Graham