Callback mechanism for listening to Pub/Sub messages

I’d love for there to be a mechanism to set up perpetual pulling and acknowledging of Cloud Pub/Sub messages, the sort of thing that might enable code like this:

# Messages are acknowledged unless DoWork raises an exception
def DoWork(message):
    print "Message payload: %s" % message.payload

worker_thread = subscription.pull(callback=DoWork)

[tseaver]

FWIW, PR’s #1636 and #1637 offer competing strategies for doing “auto-acknowlegement” of message IDs.

[tseaver]

And FTR we merged the implementation in #1636, making your example above look like:

while True:
    with subscription.auto_ack() as ack:
        for ack_id, message in list(ack.items()):
            try:
                do_something_with(message)
            except WhateverException:
                del ack[ack_id]