Pubsub Could Use Autocreate on Topics and Subscriptions

I think this will be a recurring pattern:

topic = pubsub.Topic('book-process-queue')
if not topic.exists():
    topic.create()

subscription = pubsub.Subscription('book-sub', topic)
if not subscription.exists():
    subscription.create()

So it might be a good idea to simplify it to:

topic = pubsub.Topic('book-process-queue', auto_create=True)

gcloud-node does something like this already.

[theacodes]

In the failure case, publish results in 3 requests

Correct, but the failure case only happens once.

We could just as well do a create requests.

You could, but you would need to do this every time the item is constructed.

The trade off is that assuming it exists and handling the failure cases results in 2 extra requests once, whereas looking before you leap means an extra request every single time.

In other words, a 404 for another reason should not trigger the create request

The node one only tries to create once. If the creation method fails, it returns the error to the original callback.

[dhermes]

Closing. See #949 for context.