Allow retry and timeout settings on the publisher client

[anguillanneuf]

Allow retry and timeout settings on the Publisher.

timeout= should take google.api_core.timeout.ExponentialTimeout and google.api_core.timeout.ConstantTimeout (also LogicalTimeout in future work).

The goal is be able to set custom retry and custom timeout on the PublisherClient, like this:

custom_retry = api_core.retry.Retry(
 initial=0.250, # seconds (default: 0.1)
 maximum=90.0, # seconds (default: 60.0)
 multiplier=1.45, # default: 1.3
 deadline=300.0, # seconds (default: 60.0)
 predicate=api_core.retry.if_exception_type(
 api_core.exceptions.Aborted,
 api_core.exceptions.DeadlineExceeded,
 api_core.exceptions.InternalServerError,
 api_core.exceptions.ResourceExhausted,
 api_core.exceptions.ServiceUnavailable,
 api_core.exceptions.Unknown,
 api_core.exceptions.Cancelled,
 ),
)

custom_timeout=api_core.timeout.ExponentialTimeout(
 initial=1.0, 
 maximum=10.0, 
 multiplier=1.0, 
 deadline=300.0, 
)

# Something like this:
publisher = pubsub_v1.PublisherClient(
 publisher_options = pubsub_v1.types.PublisherOptions(
 retry=custom_retry,
 timeout=custom_timeout,
 ),
)

Here are the defaults and how they are set currently: https://github.com/googleapis/googleapis/blob/3a935fab757e09c72afd4aa121147a4c97dccc3e/google/pubsub/v1/pubsub_grpc_service_config.json#L42-L62

Remember to update UPGRADING.md as well.

[cguardia]

@anguillanneuf took a bit of time to really get started here, but I'm on it now. How about other api calls that take a float timeout, like get_topic or list_topics? Should those also take the api_core timeout objects?

[anguillanneuf]

@cguardia Those can be left alone because the default settings in pubsub_grpc_service_config.json are good as they are.

Adding @kamalaboulhosn for comments too.

[kamalaboulhosn]

Thinking about it, I think in the name of simplicity, it's fine for these to apply to all of the methods in the Publisher class. It's not ideal that the admin operations are in this class, but that's a separate thing to address. The impact of using the same retry policy on the admin operations will be minimal and will easier to understand.