What's the expected behavior when using shared subscriptions in a single docker container?

[matthewadams]

We have integration tests that run against a single local docker container running vernemq (that is configured with a custom lua script for auth script, but I don't think this is involved). We want to leave the shared subscription configuration the same when running in the test configuration as when we're running in a cluster. That is, we don't want to use foo/bar/baz/# for a topic filter during integration testing, and $shared/snafu/foo/bar/baz/# when running in a cluster. The vernmq config option shared_subscription_policy is set to local_only when we run the single container, prefer_local in the cluster.

When we run with a subscriber subscribing to a shared subscription, the subscriber never gets any messages when running vernemq as a single local container. What's the expected behavior? I expected it to just work, but it doesn't appear to be. Our custom auth logs show the broker happily accepting the shared subscription without warning:

18:40:08.319 [debug] [custom-auth]     {"context":{"attempted_subscription_topics":["$shared/observation-event-mqtt-message-processor-adapter/canonical/json/observation/#"],"client_id":"site-app[gd45qkqqek2y499yyvhhdv7cfmk]"},"message":"🔗 Incoming subscription request.","timestamp":"2024-04-01 18:40:08"}
18:40:08.326 [info] [custom-auth]     {"context":{"attempted_subscription_topics":["$shared/observation-event-mqtt-message-processor-adapter/canonical/json/observation/#"],"client_id":"site-app[gd45qkqqek2y499yyvhhdv7cfmk]","subscribable_topic_filters":["#"]},"message":"✅  Allowing client topic subscriptions.","timestamp":"2024-04-01 18:40:08"}

There are many duplicated log messages like the following:

18:40:10.373 [debug] Replica meta5: Can't initialize AE exchange due to no peer available

but that is expected, I think, because there's only one broker in this configuration.

Thanks in advance.

[matthewadams]

Never mind. Typo in shared subject name. I had $shared (with a d) instead of $share. :/

[ioolkos]

@matthewadams Thanks for being faster than me :)

Btw, yes the 18:40:10.373 [debug] Replica meta5: Can't initialize AE exchange due to no peer available line is expected in a single broker (running on debug log). We could probably optimise this away on a single node, as the exchange FSMs could stay entirely inactive.