[ops] [kolla] RabbitMQ High Availability

Bogdan Dobrelya bdobreli at redhat.com
Wed Dec 8 10:46:46 UTC 2021

Please see inline

>> I read this with great interest because we are seeing this issue. Questions:
>> 1. We are running kola-ansible Train, and our RMQ version is 3.7.23. Should we be upgrading our Train clusters to use 3.8.x?
>> 2. Document [2] recommends policy '^(?!(amq\.)|(.*_fanout_)|(reply_)).*'. I don't see this in our ansible playbooks, nor in any of the config files in the RMQ container. What would this look like in Ansible, and what should the resulting container config look like?
>> 3. It appears that we are not setting "amqp_durable_queues = True". What does this setting look like in Ansible, and what file does it go into?
> Note that even having rabbit HA policies adjusted like that and its HA
> replication factor [0] decreased (e.g. to a 2), there still might be
> high churn caused by a large enough number of replicated durable RPC
> topic queues. And that might cripple the cloud down with the incurred
> I/O overhead because a durable queue requires all messages in it to be
> persisted to a disk (for all the messaging cluster replicas) before they
> are ack'ed by the broker.
> Given that said, Oslo messaging would likely require a more granular
> control for topic exchanges and the durable queues flag - to tell it to
> declare as durable only the most critical paths of a service. A single
> config setting and a single control exchange per a service might be not
> enough.

Also note that therefore, amqp_durable_queue=True requires dedicated
control exchanges configured for each service. Those that use
'openstack' as a default cannot turn the feature ON. Changing it to a
service specific might also cause upgrade impact, as described in the
topic [3].

[3] https://review.opendev.org/q/topic:scope-config-opts

> There are also race conditions with durable queues enabled, like [1]. A
> solution could be where each service declare its own dedicated control
> exchange with its own configuration.
> Finally, openstack components should add perhaps a *.next CI job to test
> it with durable queues, like [2]
> [0] https://www.rabbitmq.com/ha.html#replication-factor
> [1]
> https://zuul.opendev.org/t/openstack/build/aa514dd788f34cc1be3800e6d7dba0e8/log/controller/logs/screen-n-cpu.txt
> [2] https://review.opendev.org/c/openstack/nova/+/820523
>> Does anyone have a sample set of RMQ config files that they can share?
>> It looks like my Outlook has ruined the link; reposting:
>> [2] https://wiki.openstack.org/wiki/Large_Scale_Configuration_Rabbit
> -- 
> Best regards,
> Bogdan Dobrelya,
> Irc #bogdando

Best regards,
Bogdan Dobrelya,
Irc #bogdando

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