'
output = 'Hello World!'
response_headers = [('Content-type', 'text/plain'),
('Content-Length', str(len(output)))]
start_response(status, response_headers)
def x(y):
print os.getpid(), 'x', y
return y
print 'map call'
result = pool.map(x, [1])
print os.getpid(), 'doit', result
return [output]
Then one does get pickle errors, albeit for a different reason:
[Tue May 03 09:52:59 2011] [info] [client 127.0.0.1] mod_wsgi
(pid=33010, process='hello-1',
application='hello-1.example.com|/mptest.wsgi'): Loading WSGI script
'/Library/WebServer/Sites/hello-1/htdocs/mptest.wsgi'.
[Tue May 03 09:52:59 2011] [error] create pool
[Tue May 03 09:52:59 2011] [error] map call
[Tue May 03 09:52:59 2011] [error] Exception in thread Thread-1:
[Tue May 03 09:52:59 2011] [error] Traceback (most recent call last):
[Tue May 03 09:52:59 2011] [error] File
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/thr
eading.py,
line 522, in __bootstrap_inner
[Tue May 03 09:52:59 2011] [error] self.run()
[Tue May 03 09:52:59 2011] [error] File
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/thr
eading.py,
line 477, in run
[Tue May 03 09:52:59 2011] [error] self.__target(*self.__args,
**self.__kwargs)
[Tue May 03 09:52:59 2011] [error] File
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/mul
tiprocessing/pool.py,
line 225, in _handle_tasks
[Tue May 03 09:52:59 2011] [error] put(task)
[Tue May 03 09:52:59 2011] [error] PicklingError: Can't pickle type
'function': attribute lookup __builtin__.function failed
So, it is doing pickling in some form, which isn't going to work for
stuff in WSGI script file.
If you really want to pursue this, then suggest you move this code
outside of the WSGI script file and put it in a standard module on the
Python module search path you have set up for application.
Overall though, I would recommend against using multiprocessing module
from inside of mod_wsgi.
Graham
On 2 May 2011 23:37, Ed Summers ed.summ...@gmail.com wrote:
Hi all,
I asked this over on web-sig [1] earlier today, but am asking here
since it looks to only mod_wsgi related...
I've been trying to use the multiprocessing [2] w/ mod_wsgi and have
noticed what appears to be deadlocking behavior with body django and
web.py. I created a minimal example with web.py to demonstrate [3].
If you have mod_wsgi and web.py available, and and put something like
this in your apache config:
WSGIScriptAlias /multiprocessing /home/ed/wsgi_multiprocessing.py
AddType text/html .py
then visit:
http://localhost/
and compare with:
http://localhost/?multiprocessing=1
you should see the second URL hang.
Going forward I'm most likely going to move this functionality to an
asynchronous queue (celery, etc) but I was wondering if
multiprocessing + mod_wsgi was generally known to be something to
avoid, or if it was even forbidden somehow.
Any assistance you can provide would be welcome.
//Ed
[1]http://mail.python.org/pipermail/web-sig/2011-May/005065.html
[2]http://docs.python.org/library/multiprocessing.html
[3]https://gist.github.com/951570
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