Running pdb in daemon mode with WSGI

I am running a Python script开发者_运维问答 on Apache 2.2 with mod wsgi.

Is it possible to run pdb.set_trace() in a python script using daemon mode in wsgi?

Edit The reason I want to use daemon mode instead of embedded mode is to have the capability to reload code without having to restart the Apache server every time (which embedded mode requires). I would like to be able to use code reloading without restarting Apache everytime and still be able to use pdb...

I had the same need to be able to use the amazingly powerful pdb, dropping a pdb.set_trace() wherever I wanted to debug some part of the Python server code.

Yes, Apache spawns the WSGI application in a place where it is out of your control [1]. But I found a good compromise is to

1. maintain your Apache WSGIScriptAlias

2. and also give yourself the option of starting your Python server in a terminal as well (testing locally and not through Apache anymore in this case)

So if one uses WSGIScriptAlias somewhat like this... pointing to your python WSGI script called webserver.py

<VirtualHost *:443>

    ServerName myawesomeserver
    DocumentRoot /opt/local/apache2/htdocs

    <Directory /opt/local/apache2/htdocs>
        [...]
    </Directory>

    WSGIScriptAlias /myapp /opt/local/apache2/my_wsgi_scripts/webserver.py/

    <Directory /opt/local/apache2/my_wsgi_scripts/>
        [...]
    </Directory>

    [...]
    SSLEngine on
    [...]
</VirtualHost>                                  

And so your webserver.py can have a simple switch to go between being used by Apache and getting started up for debugging manually.

Keep a flag in your config file such as, in some settings.py:

WEBPY_WSGI_IS_ON = True

And webserver.py :

import web
import settings

urls = (
    '/', 'excellentWebClass',
    '/store', 'evenClassier',)

if settings.WEBPY_WSGI_IS_ON is True:
    # MODE #1: Non-interactive web.py ; using WSGI
    #   So whenever true, the Web.py application here will talk wsgi.
    application = web.application(urls, globals()).wsgifunc()

class excellentWebClass:
    def GET(self, name):

        # Drop a pdb  wherever you want only if running manually from terminal.
        pdb.set_trace()

        try:
            f = open (name)
            return f.read()
        except IOError:
            print 'Error: No such file %s' % name

if __name__ == "__main__":

    # MODE #2: Interactive web.py , for debugging.
    #   Here you call it directly.  
    app = web.application(urls, globals())
    app.run()

So when you want to test out your webserver interactively, you just run it from a terminal,

$ python webserver.py 8080
starting web...
http://0.0.0.0:8080/

[1] Footnote: There are some really complex ways of getting Apache child processes under your control, but I think the above is much simpler if you just want to debug your Python server code. And if there are actually easy ways, then I would love to learn about those too.