CODEWITHSUNDEEP
pythonwsgiuwsgi
chacham15
chacham15

Reputation: 14251

What does this uWSGI error mean?

from gevent import monkey
monkey.patch_all()

import gevent
from gevent import pywsgi
from gevent import queue
import redis

REDIS_CONNECTION_POOL = redis.ConnectionPool(host=REDIS_HOST, port=REDIS_PORT, db=REDIS_DB)

def redis_wait(environ, body, channel, wait_once):

    server = redis.Redis(connection_pool=REDIS_CONNECTION_POOL)
    client = server.pubsub()

    client.subscribe(channel)

    messages = client.listen()

    while True:
        message = messages.next()

This is the error:

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/gevent/greenlet.py", line 327, in run
    result = self._run(*self.args, **self.kwargs)
  File "/home/ubuntu/www/app.wsgi", line 110, in wait_messages
    redis_wait(environ, body, channel, False)
  File "/home/ubuntu/www/app.wsgi", line 47, in redis_wait
    message = messages.next()
StopIteration
<Greenlet at 0x1c190f0: wait_messages({}, ['5386E49C1CEB16573ACBD90566F3B740983768CB,1358532, <Queue at 0x19fd6d0>, '1410290151', None)> failed with StopIteration

I have tried to google the error, but nothing comes up. The error only occurs intermittently. Does anyone know what it means? Is it a timeout of some sort perhaps?

Upvotes: 0

Views: 218

Answers (1)

rmunn
rmunn

Reputation: 36698

StopIteration is the exception that Python throws when an iterator (such as messages) has reached the end of its values. It is not an error, but a normal, expected condition that will be automatically handled by Python in some circumstances. For example, if you loop over the iterator using a for loop like so:

for message in messages:
    print message # Or do something with it

then the StopIteration exception will end the for loop normally.

However, a while loop does not handle StopIteration itself, but lets it continue through to your code so that you can handle it in whatever way you see fit. Your code is currently not handling it, so the exception ends up terminating your program.

Replace your while True: message = messages.next() loop with for message in messages and everything should work.

More reading on iterators, generators, and StopIteration:

Upvotes: 1

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