Migrating classic queues to quorum

The production checklist mandates quorum queues (with delivery_limit=) for money/order flows — but RabbitMQ cannot change a queue's x-queue-type in place, and re-declaring an existing classic queue with quorum arguments fails startup with a 406. rabbitkit topology migrate is the supported path across that gap.

Every strategy is create new → move messages → cut over, driven through the management API with the rabbitmq_shovel plugin (a missing plugin is detected up front with a clear error naming rabbitmq-plugins enable rabbitmq_shovel).

Plan first (never mutates)

rabbitkit topology migrate myapp.main:broker \
  --url http://user:pass@rabbit:15672 --amqp-url amqp://user:pass@rabbit/

The default mode compares each route's declared queue type against the live one and, for every classic→quorum mismatch, prints an ordered runbook and writes a JSON snapshot of the queue's bindings and arguments — the rollback artifact every destructive step can be reversed from.

Execute: drain-cutover (bounded downtime, keeps the queue name)

rabbitkit topology migrate myapp.main:broker --execute --strategy drain-cutover ...

Per queue, eleven checkpointed steps: verify zero consumers (refused otherwise; --force exists and is dangerous), snapshot bindings, create a temporary quorum queue, shovel old→tmp, wait empty, delete the old queue, re-declare it with quorum arguments, recreate bindings from the snapshot, shovel tmp→back, wait empty, delete tmp. Message counts are re-verified before every destructive step; progress is checkpointed to .rabbitkit-migrate.json after each step so a crashed run continues with --resume. --dry-run prints every management call without issuing any.

Execute: bridge (near-zero downtime, new name)

Creates {queue}.q2 as quorum with duplicated bindings and deletes nothing — move consumers to the new name via a config change, let the shovel drain stragglers, retire the old queue yourself.

	drain-cutover	bridge
Downtime	bounded (consumers stopped for the drain)	near zero
Queue name	preserved	changes (.q2)
Deletes the old queue	yes (after verified-empty)	no

Useful flags: --queue (one queue), --vhost, --timeout (drain-wait bound, default 300s), --state-file, --snapshot-file.