How to diagnose intermittent uwsgi errors? - uwsgi

Question

First let me briefly describe our set up before I ask the question proper:
We have a web application server (virtual machine) running a django application. nginx at the front, uwsgi running under that, then a newrelic application wrapper followed by django et al., database is a separate postgresql server located via smartstack (synapse/nerve)
The issue we face is that occasionally (happened once 2 weeks ago, and twice in the last 2 days), one or two of the uwsgi worker processes will trip up and start producing "django.db.utils.InterfaceError: connection already closed" on most of their requests.
slightly redacted stack trace (user and application_name):
Traceback (most recent call last):
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/newrelic-2.8.0.7/newrelic/api/web_transaction.py", line 863, in __call__
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/newrelic-2.8.0.7/newrelic/api/function_trace.py", line 90, in literal_wrapper
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/newrelic-2.8.0.7/newrelic/api/web_transaction.py", line 752, in __call__
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/core/handlers/wsgi.py", line 194, in __call__
signals.request_started.send(sender=self.__class__)
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 185, in send
response = receiver(signal=self, sender=sender, **named)
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/__init__.py", line 91, in close_old_connections
conn.abort()
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/backends/__init__.py", line 374, in abort
self.rollback()
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/backends/__init__.py", line 177, in rollback
self._rollback()
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/backends/__init__.py", line 141, in _rollback
return self.connection.rollback()
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/utils.py", line 99, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/django/db/backends/__init__.py", line 141, in _rollback
return self.connection.rollback()
File "/home/user/webapps/application_name/local/lib/python2.7/site-packages/newrelic-2.8.0.7/newrelic/hooks/database_dbapi2.py", line 82, in rollback
django.db.utils.InterfaceError: connection already closed
The stack trace never gets in to our application, it only touches new relic and django. Once a worker trips, it doesn't recover and all further requests result in 500's in the uwsgi logs and 502's on the front side. I assume database connectivity is fine because the sibling workers continue to function normally, and restarting uwsgi instantly fixes the problem.
My question is how one would go about diagnosing this issue to pinpoint the root cause, I have checked everything I know how to check (memory, cpu, logs, database connectivity) and some things I don't fully understand but am trying to read up on (file descriptors mainly).
For now I updated new relic (stack trace is older version) as it's the only thing I felt I could do.
I would appreciate any feedback, many google searches have proved fruitless.
replies may be slightly delayed, my timezone says it's time to sleep. Also, apologies if this should be on serverfault or something, I just figured it's closer to an application debug issue than a server config issue.