Steps

Confirm the broker is on RabbitMQ 3.13+, which added MQTT 5.0 support to the built-in rabbitmq_mqtt plugin alongside existing 3.1/3.1.1 support
Expect QoS 2 publishes from an MQTT 3.x client to be silently downgraded to QoS 1; expect an MQTT 5.0 client publishing QoS 2 to be disconnected with reason code 155 ('QoS not supported')
Do not rely on MQTT 5.0 shared subscriptions ($share/<group>/<topic>) — RabbitMQ's MQTT plugin does not support them
If retained messages are needed, choose a store via mqtt.retained_message_store (rabbit_mqtt_retained_msg_store_ets for RAM or the disk-backed default rabbit_mqtt_retained_msg_store_dets, capped at 2GB per vhost)
Cap durable session lifetime with mqtt.max_session_expiry_interval_seconds (default 86400s/1 day), which bounds whatever Session Expiry Interval the client requests
If moving durable MQTT session queues to quorum type, set mqtt.durable_queue_type = quorum only on a fresh cluster before any client creates a durable subscription

Known gotchas

Retained-message stores are node-local and not replicated across the cluster, so a client connecting to a different node won't see retained messages published via another node, and wildcard (#/+) subscriptions never receive retained messages at all
Changing mqtt.durable_queue_type on a cluster that already has durable subscriptions causes queue-type-mismatch failures, since queue type is immutable after declaration
RabbitMQ does not support MQTT 5.0 re-authentication (AUTH packets); an expiring token gets the client disconnected with reason code 160 instead of renegotiated

Prevent MQTT 5.0 message echo in a bridge or shared-state topic using No Local, Retain As Published, and Retain Handling subscription options

iot · 5 steps · unrated

Set up MQTT 5.0 shared subscriptions on EMQX to load-balance messages across a consumer group

emqx · 6 steps · unrated

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Understand RabbitMQ MQTT plugin behavior differences when using MQTT 5.0 instead of 3.1.1, including QoS 2 and shared subscriptions

Steps

Known gotchas

Related routes

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