Core metrics: remove backing_queue_status from the core metrics

[dcorbacho]

They will not show in the HTTP API GET /api/queues, but are still available whenever the queue info is requested through the rabbit_amqqueue API.

GET /api/queues is widely used and abused without pagination and often to retrieve just a single metric. This change will considerable reduce the size of the JSON response when querying 10s or 100s of queues, and it should not impact the operation of the system as backing_queue_status is an internal metric on which no monitoring tool should rely on.

References #9437

Types of Changes

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• I have added tests that prove my fix is effective or that my feature works
• All tests pass locally with my changes
• If relevant, I have added necessary documentation to https://github.com/rabbitmq/rabbitmq-website
• If relevant, I have added this change to the first version(s) in release-notes that I expect to introduce it

[gomoripeti]

I wonder how the mgmt UI queries individual queue info (on the single queue page)? As it gets the displayed "queue storage version" from the backing_queue_status field. (https://github.com/rabbitmq/rabbitmq-server/blob/main/deps/rabbitmq_management/priv/www/js/formatters.js#L198)

[dcorbacho]

Thanks for the heads up @gomoripeti, that one is going to be reintroduced as a top-level key.

[H4rry12]

Hello,

I am trying to implement drain time measurement fot Rabbitmq queues.
Before this change I used script simillar to https://github.com/sensu-plugins/sensu-plugins-rabbitmq/blob/master/bin/check-rabbitmq-queue-drain-time.rb#L137
secs_till_empty = queue['messages'] / queue['backing_queue_status']['avg_egress_rate']

I there any way how to obtain backing_queue_status now? How i can access mentioned "rabbit_amqqueue API"
I am not able to find some solution...

[michaelklishin]

@H4rry12 you can obtain a queue's ingress and egress rates without using this leaked (and now removed) implementation detail. That's how management UI is still able to provide them, it does not use any internal or hidden API endpoints.

Start with localhost:15672/api/ (assuming a locally running node). Do not use GET /api/queues to only get one metric of one queue, that's extremely expensive and wasteful.

[jpanynines]

@michaelklishin on the commit message is said that we can still get these backing_queue_status metrics using amqqueue API. Can you give us more information on how to do that? I used the bunny library to connect to an rabbitmq 3.13 server and did not saw any way to get this information. Maybe I am using the wrong lib? Thank you in advance for your time.

[michaelklishin]

The metrics removed here are implementation details. They are not supposed to be used. In fact, when CQv1 are removed completely (most likely in 4.1), they won't be available.

[michaelklishin]

Node metrics are not consumed using messaging protocol libraries. See Monitoring.