class 'psycopg2.InterfaceError': connection already closed-Collection of common programming errors

I am pulling my hair over this and am about ready to do something dirty.

I am running nginx + django + postgresql. Half the time I am trying to test my site and open a page, I get the following:

   Python 2.7.2: /home/webapp/newavenue/bin/python
Fri Feb 24 08:28:58 2012
A problem occurred in a Python script. Here is the sequence of function calls leading up to the error, in the order they occurred.

 /home/webapp/newavenue/lib/python2.7/site-packages/flup/server/fcgi_base.py in run(self=)
    572             
    573         try:
=>  574             protocolStatus, appStatus = self.server.handler(self)
    575         except:
    576             traceback.print_exc(file=self.stderr)
protocolStatus undefined, appStatus undefined, self = , self.server = , self.server.handler = 
 /home/webapp/newavenue/lib/python2.7/site-packages/flup/server/fcgi_base.py in handler(self=, req=)
   1157         try:
   1158             try:
=> 1159                 result = self.application(environ, start_response)
   1160                 try:
   1161                     for data in result:
result = None, self = , self.application = , environ = {'CONTENT_LENGTH': '', 'CONTENT_TYPE': '', 'HTTP_ACCEPT': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'HTTP_ACCEPT_CHARSET': 'ISO-8859-1,utf-8;q=0.7,*;q=0.3', 'HTTP_ACCEPT_ENCODING': 'gzip,deflate,sdch', 'HTTP_ACCEPT_LANGUAGE': 'en-US,en;q=0.8', 'HTTP_CACHE_CONTROL': 'max-age=0', 'HTTP_CONNECTION': 'keep-alive', 'HTTP_COOKIE': 'csrftoken=8a0176b368b17af00a8563b5f95b134b; sess...e5bdd0d0a4e3092e7a9abd0029c02; django_language=en', 'HTTP_HOST': 'newavedev.zapto.org', ...}, start_response = 
 /home/webapp/newavenue/lib/python2.7/site-packages/django/core/handlers/wsgi.py in __call__(self=, environ={'CONTENT_LENGTH': '', 'CONTENT_TYPE': '', 'HTTP_ACCEPT': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'HTTP_ACCEPT_CHARSET': 'ISO-8859-1,utf-8;q=0.7,*;q=0.3', 'HTTP_ACCEPT_ENCODING': 'gzip,deflate,sdch', 'HTTP_ACCEPT_LANGUAGE': 'en-US,en;q=0.8', 'HTTP_CACHE_CONTROL': 'max-age=0', 'HTTP_CONNECTION': 'keep-alive', 'HTTP_COOKIE': 'csrftoken=8a0176b368b17af00a8563b5f95b134b; sess...e5bdd0d0a4e3092e7a9abd0029c02; django_language=en', 'HTTP_HOST': 'newavedev.zapto.org', ...}, start_response=)
    272                 response = self.get_response(request)
    273         finally:
=>  274             signals.request_finished.send(sender=self.__class__)
    275 
    276         try:
global signals = , signals.request_finished = , signals.request_finished.send = , sender undefined, self = , self.__class__ = 
 /home/webapp/newavenue/lib/python2.7/site-packages/django/dispatch/dispatcher.py in send(self=, sender=, **named={})
    170 
    171         for receiver in self._live_receivers(_make_id(sender)):
=>  172             response = receiver(signal=self, sender=sender, **named)
    173             responses.append((receiver, response))
    174         return responses
response undefined, receiver = , signal undefined, self = , sender = , named = {}
 /home/webapp/newavenue/lib/python2.7/site-packages/django/db/__init__.py in close_connection(**kwargs={'sender': , 'signal': })
     83 def close_connection(**kwargs):
     84     for conn in connections.all():
=>   85         conn.close()
     86 signals.request_finished.connect(close_connection)
     87 
conn = , conn.close = 
 /home/webapp/newavenue/lib/python2.7/site-packages/django/db/backends/__init__.py in close(self=)
    242     def close(self):
    243         if self.connection is not None:
=>  244             self.connection.close()
    245             self.connection = None
    246 
self = , self.connection = , self.connection.close = 
: connection already closed 
      args = ('connection already closed',) 
      cursor = None 
      message = 'connection already closed' 
      pgcode = None 
      pgerror = None

The server is run with the following to generate the preceding flup traceback report:

python manage.py runfcgi host=127.0.0.1 port=8000 debug=False

Could I just get around this by patching in something like: “try: self.connection.close(), except: pass” around that offending line? It would probably work but I think it sounds dirty (messing with core) and I would like to try to find an alternative solution.

Edit: Considering this guy’s approach too: commenting it out: http://osdir.com/ml/DjangoUsers/2009-04/msg01647.html

1. I think I got around the problem. This is not really a solution to the flup-psycopg2 setup but a sidestepping alternative. I switched from using fcgi to gunicorn and also wrapped the self.connection.close() line with “try: self.connection.close(), except: pass”. This also solved a 502 Bad Gateway problem I was having with nginx.

   Also, it seems my site runs a little faster, which is always a sweet side effect.