On 22 March 2011 09:35, Eric Lemoine <[email protected]> wrote:
> On Monday, March 21, 2011, Graham Dumpleton <[email protected]>
> wrote:
>> Read:
>>
>> http://code.google.com/p/modwsgi/wiki/ProcessesAndThreading
>>
>> Embedded mode on UNIX is always going to be multiprocess, thus these
>> are likely the script being loaded in different processes.
>> Specifically, one will be the original page and the other a request
>> for static resources via the application or a request for favicon.ico
>> by the browser.
>
>
> Yes I figured that out a couple hours after I wrote to the list.
>
> ...
>
> Below Is the modwsgi config I'm now considering (untested yet). In my
> case I want to have multiple instances of the same WSGI app in the
> same virtual host, and I want to isolate these instances as much as
> possible.
>
> ---
> #
> # Use mod_wsgi's daemon mode.
> # The WSGI app instance is assigned a specific process group.
> #
> #
>
> # define a process group
> WSGIProcessDaemon ${instanceid} processes=1 threads=15
Directive is WSGIDaemonProcess.
Also don't use 'processes=1' if the application will run in one process.
I know this sounds counter intuitive, but the default is actually for
one process anyway.
Use of 'processes=1' does also create one process, but use of the
'processes' option with any value causes 'wsgi.multiprocess' to be
True. So, just allow the default single process to be created. Use of
'processes=1' should only be used as back door for flagging it is
multi process if loading balancing application across multiple
servers, or splitting a single application across multiple daemon
process groups.
The default number of threads is also already 15.
> # define the path to the WSGI app
> WSGIScriptAlias /${instanceid}/wsgi /path/to/script.wsgi
>
> # assign the WSGI app instance the process group defined above
> # we put the WSGI app instance in the global application group so it
> is always executed within in the main interpreter
> <Location /${instanceid}/wsgi>
> WSGIProcessGroup ${instanceid}
> WSGIApplicationGroup %{GLOBAL}
> </Location>
So long as you are using mod_wsgi 3.0 or later, easier to get rid of
this Location block and use:
WSGIScriptAlias /${instanceid}/wsgi /path/to/script.wsgi
process-group=${instanceid} application-group=%{GLOBAL}
Just be aware that supplying process group and application group as
options to WSGIScriptAlias will also cause the WSGI script file to be
preloaded when daemon processes startup and not on first request.
Although unlikely, this could be an issue for some applications.
Graham
> ---
>
>
> I'd be happy to have your opinion on this approach.
>
> Thanks a lot for your support!
>
> --
> Eric Lemoine
>
> Camptocamp France SAS
> Savoie Technolac, BP 352
> 73377 Le Bourget du Lac, Cedex
>
> Tel : 00 33 4 79 44 44 96
> Mail : [email protected]
> http://www.camptocamp.com
>
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