Oban requires pubsub to function, particularly Web, but it doesn’t need to use Postgres. In fact, we recommend switching to an alternate notifier (like PG) in the Web installation guide.
It’s common for large payloads to be exchanged during shutdown, when the nodes shutting down hand off the stats history to new nodes. That’s one of several reasons we recommend the notifier for Web (as linked above), and in the scaling guide.
The Gossip plugin was deprecated, as was Web’s Stats plugin, and they were replaced by the oban_met package. That still uses the oban_gossip channel to communicate about queue activity.
