[pubSub] tell when to use subscription.reload()

[ensonic]

The api docs don't mention when one should use this api (when is my local config out of sync), e.g. is there are exception I should react to?

[tseaver]

@ensonic Thanks for the report!

The two bits of state which Subscription.reload() fetches from the server are the ack_deadline and push_endpoint attributes. "Normal" use of the subscription (pulling events) isn't affected by those variables. Any time your app does need to know their values for some reason (e.g., before calling modify_push_endpoint() to see what the current state is), then it is best to call reload() first.

[ensonic]

Thanks for the info. Adding this bit to the docs would be nice.

The reason I looked at the API was that I wonder if a subscription can go 'stale'. I have a case where a subscriber seems to be getting 'old' messages. The subscriber is ack'ing the messages. By 'old', I mean the message.service_timestamp is e.g. 3 hours behind. E.g.

[2017-02-22 14:13:14,361] INFO:root:msg-id: 110510709003979, ts: 2017-02-22T11:42:14.299000Z, topic: topic1
[2017-02-22 14:13:16,981] INFO:root:msg-id: 110519798495214, ts: 2017-02-22T14:11:24.310000Z, topic: topic1

Each topic is published by a gke instance. When I log into each instance the clock is looking alright. The service_timestamp is set here:
https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/pubsub/google/cloud/pubsub/message.py#L90

Edit: I think I am bitten by the default 'max_messages=1' for subscription.pull(). Unfortunately there is no easy way to 'flush' a topic :/.