Queries regarding RabbitMQ clustering with 2 nodes

[Dhamotharan]

Hi Team,

I need some info regarding RabbitMQ clustering concept.

1. My application will be having 2 or 3 nodes of RabbitMQ instance depends on usage. Can we use quorum queues with 2 nodes(I have read it cannot be used with 2nodes , minimum is 3 nodes). If we have cluster with 2nodes, what type of queue can be used?

2. Producers and consumers will be running from all nodes with single active consumer case. 

For this use case, what is the best practise. Your suggestion would be helpful for me to use this RabbitMQ cluster in my application.

Thanks in advance,

Dhamotharan.

[Dhamotharan]

• RabbitMQ version - 3.10
• Erlang version - 24.3
• Operating system running RabbitMQ, and version - Windows Server 2016
• Are you using a cluster, and if so, how many nodes - Clustering with 2 nodes and had a federation policy for HA when one node goes down

[Michal Kuratczyk]

Hi,

1. Do not use 2-node clusters.

2. Do not use mirrored queues

3. Do not autoscale RabbitMQ clusters based on traffic (it might be possible, but it's certainly not trivial)

4. If you want replicated queues, use quorum queues (or streams)

Best,

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Michał

RabbitMQ team

[Dhamotharan]

Hi,

In my use the number of nodes can be vary. Can you please respond below query.

1. If we need to cluster 2 nodes, then what is the possible way?

2. If I use quorum queues with even number of nodes (say 4), then tolerated node failure will be 1 that means, if one master node goes to another node will become master but what if that another master node also becomes down?

3. Why I should not use classic queue with mirroring policy?

Thanks,

Dhamotharan

[Michal Kuratczyk]

Mirroring policies will be removed from RabbitMQ next year. If you decide to use them, you will need to migrate off of them soon.

They are being removed because they have some fundamental flaws that can't be fixed.

Quorum queues are a replacement that solves the aforementioned issues. Using the RAFT consensus algorithm is a key part of the solution.

RAFT requires an odd number of nodes. That's not specific to RabbitMQ - you will see the same requirement in other RAFT-based software, for example:

https://etcd.io/docs/v3.3/faq/#why-an-odd-number-of-cluster-members

https://developer.hashicorp.com/consul/docs/architecture/consensus

Do not use 2 node clusters.

Best,

To view this discussion on the web, visit https://groups.google.com/d/msgid/rabbitmq-users/afbf3fc0-fe7c-44e0-b81f-4d3d1ade47bfn%40googlegroups.com.

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Michał

RabbitMQ team