[Python] mod_wsgi: Error "No such directory" for shutil.rmtree() after mkdtemp()

I'm really confusing about multiple thread in mod_wsgi, even after reading this document

The main problem is that, how does mod_wsgi call my python scripts?

To make my question clear, i will conclude it to questions below

Suppose I have server configured like this:

WSGIDaemonProcess XXX.com processes=12 threads=20 display-name=%{GROUP}
WSGIProcessGroup XXX.com
WSGIScriptAlias /sign /XXX/Http/upload.wsgi


And I'm using prefork MPM

And my /XXX/Http/upload.wsgi looks like this:

class app(object):

def __init__(self):
pass

def __call__(self, environ, start_response):
temp_unsign = tempfile.mkdtemp()
temp_signed = tempfile.mkdtemp()

try:
response_headers = [('Content-type', 'text/plain;charset=UTF-8'),('Content-Length', str(len('123')))]
status = '200 OK'
start_response(status, response_headers)

return ['123']
finally:
shutil.rmtree(temp_unsign)
shutil.rmtree(temp_signed)

application = app()


Them my questions are:

1. If there're 5 requests from different IP at the same time, how many app instances will be there? One instance ? Or one instance per request
2. What if there're 5 requests from same IP and same computer at the same time?
3. Does all 5 __call__ methods run in 5 different threads?

I ask this because I always get error No such directory when execute shutil.rmtree.

And of course, i can't understand how does mod_wsgi actually work in the matter of multiple thread

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