oslo.messaging: Notification listener pools¶
The idea is that you can have multiple groups/pools of listeners consuming notifications and that each group/pool only receives one copy of each notification.
Currently if two applications use the oslo.messaging notification listener and want to subscribe to the same topic, they steal messages from each other.
The current workaround is to configure the notifier part to publish the message twice on different topic. This confuses a lot of people and this is undocumented.
So part of the purpose of this BP is a bit hardcoded into oslo.messaging and have bad side effect. The proposal will fix that.
We need to add a pool parameter for the messaging.get_notification_listener() API in order to support this.
In all AMQP drivers, this is implemented by using the pool name as the queue name for consume from the topic. To keep backward compatibility, by default, the topic name will continue to be used as the pool/queue name.
Documents the workaround.
Impact on Existing APIs¶
oslo.messaging.get_notification_listener will get a new parameter ‘pool’ to configure the pool name.
- Primary assignee:
- Other contributors:
Works already done: https://review.openstack.org/125112
Anticipated API Stabilization¶
The new pool parameter will be documented.
Code in review: https://review.openstack.org/#/c/125112/
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