What Are Quorum Queues?

• Quorum Queues are distributed queues built on the Raft consensus algorithm.
• They are designed for high availability, durability, and data safety by replicating messages across multiple nodes in a RabbitMQ cluster.
• Its a replacement of Mirrored Queues.

Key Characteristics

1. Replication:
   • Messages are replicated across a quorum (a majority of nodes).
   • A quorum consists of an odd number of replicas (e.g., 3, 5, 7) to ensure a majority can elect a leader during failovers.
2. Leader-Follower Architecture:
   • Each Quorum Queue has one leader and multiple followers.
   • The leader handles all write and read operations, while followers replicate messages and provide redundancy.
3. Durability:
   • Messages are written to disk on all quorum nodes, ensuring persistence even if nodes fail.
4. High Availability:
   • If the leader node fails, RabbitMQ elects a new leader from the remaining quorum, ensuring continued operation.
5. Consistency:
   • Quorum Queues prioritize consistency over availability.
   • Messages are acknowledged only after replication is successful on a majority of nodes.
6. Message Ordering:
   • Message ordering is preserved during normal operations but may be disrupted during leader failovers.

Use Cases

• Mission-Critical Applications – Systems where message loss is unacceptable (e.g., financial transactions, order processing).
• Distributed Systems – Environments requiring high availability and fault tolerance.
• Data Safety – Applications prioritizing consistency over throughput (e.g., event logs, audit trails).

Setups

Using rabbitmqctl

rabbitmqctl add_queue quorum_queue --type quorum

Using python

channel.queue_declare(queue="quorum_queue", arguments={"x-queue-type": "quorum"})

References:

1. https://www.rabbitmq.com/docs/quorum-queues