Hi,
I'm thinking of using wsgi to do a simple framework for some webapps I
have in mind. I'm trying to understand how mod_wsgi handles global data
and what kind of thread synchronisation I need to contorl access to the
global data.
I wrote this very simple app to test global variables...
counter=0
def application(environ, start_response) :
global counter
status='200 OK'
response_headers=[('Content-type', 'text/plain')]
start_response(status, response_headers)
counter+=1
return ['counter is '+str(counter)+'\n']
I had the following in my apache conf...
WSGIDaemonProcess myserver threads=2 maximum-requests=75
So I should have 1 process with 2 threads in it.
When I repeatedly hit the browser, I see the counter go up as expected
but then it goes back to 1 after 50 hits.
I'm curious how excactly the threads & processes work regarding global
variables.
Why does it reset after 50 hits ?
Is it possible to write some kind of thread-id in my output so I know
which of the 2 threads it hits?
If i have threads recycling after the 75 requests, will that also reset
the global variable each time one of the threads hits maximum-request
?...although the global variable seems to be resetting now ...why ? )
I'm guessing that to avoid race conditions I'd need to use the threading
module and put a lock around the counter increment...or do the mod_wsgi
threads not work like that ? i.e. each daemon thread has it's own self
contained python interpreter so no data is shared between the mod_wsgi
threads ?
Any answers on the above greatly appreciated.
Regards,
Emyr
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