'Subscription.pull(return_immedately=False, max_messages=2)' returns immediately :(

[tseaver]

Sporadic regression failure:

======================================================================

ERROR: test_message_pull_mode_e2e (pubsub.TestPubsub)

----------------------------------------------------------------------

Traceback (most recent call last):

 File "/home/travis/build/GoogleCloudPlatform/gcloud-python/regression/pubsub.py", line 123, in test_message_pull_mode_e2e

 received = subscription.pull(max_messages=2)

 File "/home/travis/build/GoogleCloudPlatform/gcloud-python/.tox/regression3/lib/python3.4/site-packages/gcloud/pubsub/subscription.py", line 191, in pull

 for info in response['receivedMessages']]

KeyError: 'receivedMessages'

AFAICT, this is actually a back-end bug -- we are passing the returnImmediately flag through correctly. @tmatsuo can you report it to the pubsub back-end team?

However, we should harden against the missing key in the response, for the case when returnImmediately is True, and there are no messages.

[tmatsuo]

I assume you are passing returnImmediately = False and getting an empty messages.

Well, it can still happen since requests with returnImmediately=False still timeout (and thus you get an empty response), also we don't have any SLAs for the message delivery latency, although most of the cases messages are arrived in near real time.

[tseaver]

@tmatsuo you are correct: we are passing returnImmediately=False. I would have expected the call to block indefinitely in that case. based on the language of the pull API docs.

If this is specified as true the system will respond immediately even if it is not able to return a message in the Pull response. Otherwise the system is allowed to wait until at least one message is available rather than returning no messages. The client may cancel the request if it does not wish to wait any longer for the response.

If that is not expected behavior, I'm not sure we can write an end-to-end regression test which is not going to fail sporadically.

[tseaver]

#899 fixes the KeyError in the case that the back-end returns no messages. Leaving the issue open because we still have the potential regression test failure due to timeouts on the back-end.

[dhermes]

Closing and merging into #1085