Re: Cleaning up redis connection after client disconnects from streaming response

After a lot of banging on things and reading framework code, I've found what I

think is the right answer to this question.

1. According to the WSGI PEP, if your application returns an iterator with a

close() method, it should be called by the WSGI server once the response has

finished. Django supports this too. That's a natural place to do the Redis

connection cleanup that I need.

2. There's a bug in Python's wsgiref implementation, and by extension in

Django's 'runserver', that causes close() to be skipped if the client

disconnects from the server mid-stream. See http://bugs.python.org/issue16220.

I've submitted a patch.

3. Even if the server honors close(), it won't be called until a write to the

client actually fails. If your iterator is blocked waiting on the pubsub and

not sending anything, close() won't be called. I've worked around this by

sending a no-op message into the pubsub each time a client connects. That way

when a browser does a normal reconnect, the now-defunct threads will try to

write to their closed connections, throw an exception, then get cleaned up when

the server calls close(). The SSE spec says that any line beginning with a

colon is a comment that should be ignored, so I'm just sending ":\n" as my

no-op message to flush out stale clients.

Sample code for doing this is posted on the Stack Overflow page where I also

posted this question.  See

http://stackoverflow.com/questions/12853067/django-cleaning-up-redis-connection-after-client-disconnects-from-stream

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