I didn't add a test case for this since it's a very straightforward change. This can be tested manually by creating a config file config.conf with queue_types.stream.enabled = false, running the broker (make run-broker RABBITMQ_CONFIG_FILE=config.conf) and trying to declare a stream queue through either the management UI or with perf-test --stream-queue.

I also didn't add a config option for the MQTT QoS0 queue type since I think that queue type is more of an implementation detail and not worth controlling other than with the feature flag.

This PR prevents streams from being declared in some, but not all, ways. If you just run stream-perf-test, it declares a stream without problems, despite queue_types.stream.enabled = false.

Moreover, trying to disable classic queues seems to prevent a node from booting at all. Just trying make run-broker with queue_types.classic.enabled = false leads to:

error:{badmatch,{error,queue_type_feature_flag_is_not_enabled}}

    rabbit:insert_default_data/0, line 1236
    rabbit_boot_steps:-run_step/2-lc$^0/1-0-/2, line 53
    rabbit_boot_steps:run_step/2, line 60
    rabbit_boot_steps:-run_boot_steps/1-lc$^0/1-0-/1, line 24
    rabbit_boot_steps:run_boot_steps/1, line 25
    rabbit:start/2, line 1009
    application_master:start_it_old/4, line 299

For the streams protocol it looks like we'll need to add a check of rabbit_queue_type:is_enabled/1 in rabbit_stream_manager:do_create_stream/4 so it behaves more like rabbit_amqqueue:declare/7.

For the failure to boot it looks like this check fails when adding the default vhost:

So we can't add vhosts where the default queue type is not enabled. I think it might be more reasonable to warn in that situation since you might always explicitly declare your queue types - IMO is_enabled/1 should only stop attempts to declare a queue and not block vhost creation.

I will send some follow-ups. Thanks @mkuratczyk!