Google Pub/Sub: Configurable host (for ordering)

[LukBed]

If ordering is required on Pub/Sub then messages must be sent only to specific region (using regional Pub/Sub endpoint). If two messages with the same orderng key are sent to two different regions, then ordering is not guaranteed.

All quotes from Pub/Sub documentation.
https://cloud.google.com/pubsub/docs/ordering
https://cloud.google.com/pubsub/docs/resource-location-restriction

If messages have the same ordering key and are in the same region, you can enable message ordering and receive the messages in the order that the Pub/Sub service receives them.

It's possible to restrict region on topic level

If you publish messages to the global Pub/Sub endpoint, Pub/Sub automatically stores the messages in the nearest Google Cloud region. Pub/Sub's topic message storage policy offers a way to ensure that messages published to a topic are never persisted outside a set of Google Cloud regions you specify, regardless of where the publish requests originate. When multiple regions are allowed by the policy, Pub/Sub chooses the nearest allowed region.

But:

If you publish a message with an ordering key and the message storage policy excludes the nearest region, the Pub/Sub service returns an error.

So the best solution is specify region when message is published.

PR constains proposition with extending publish flow, by new optional parameter with Pub/Sub host.

Example usage:
GooglePubSub.publish(topic, config, Some("europe-west1-pubsub.googleapis.com"));

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[ennru]

Wouldn't String be enough? If you don't want to pass a host you'd use the other overload?

[LukBed]

Right, changed

[ennru]

LGTM.

[ennru]

Thank you!