rabbitmqctl in livenessProbe and readinessProbe keep RabbitMQ nodes at ~30% CPU when idle

**Category:**

Kubernetes apps

**Type:**

- [ ] Bug
- [X] Feature Request
- [ ] Process

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Currently, RabbitMQ liveness checks are done using `exec` `rabbitmqctl status`. Launching `rabbitmqctl` costs 100% of a CPU for ~1.5s on an n1-standard-2 instance. That's because Erlang takes a long time to start up.

livenessProbe and readinessProbe each run every 10s. Each takes 1.5s to complete. Together, they cost 30% of all my pods' available CPU cycles.

There's an alternative: `curl`. The management API includes `/api/aliveness-test/vhost` which returns 200 `{"status":"ok"}` on success and 200 (yes, 200) `{"status":"failed",...}`. See https://rawcdn.githack.com/rabbitmq/rabbitmq-management/v3.7.8/priv/www/api/index.html

I propose adding `curl` (or some other HTTP-request command) to the RabbitMQ image and changing the livenessProbe and readinessProbe to use curl instead of rabbitmqctl. I expect RabbitMQ will be 30% more responsive as a result.

The issue points to the RabbitMQ image and its livenessProbe/readinessProbe definitions; start by locating those deployment and image entry points and checking how the probes are configured. Verify that an HTTP-request command can call the management API's aliveness endpoint and that both probes retain correct success and failure behavior, then measure idle CPU impact.

Written by the indexing model from the issue text.