lifecycle sleep does not work

[nenych]

Describe the bug

If we want to set the lifecycle hook to sleep before the termination - the operator will not create the resource.
Note: exec with sleep works fine.

To Reproduce

Steps to reproduce the behavior:

1. Create resource
2. No resource is created by the operator

Include any YAML or manifest necessary to reproduce the problem.

apiVersion: "rabbitmq.com/v1beta1"
kind: "RabbitmqCluster"
spec:
  override:
    statefulSet:
      spec:
        template:
          spec:
            containers:
              - name: "rabbitmq"
                lifecycle:
                  preStop:
                    sleep:
                      seconds: 10

Expected behavior
RabbitMQ pod with the lifecycle hook

Screenshots

If applicable, add screenshots to help explain your problem.

Version and environment information

• RabbitMQ: 3.10.7-debian-11-r8
• RabbitMQ Cluster Operator: 2.9.0-debian-12-r2
• Kubernetes: v1.30.5
• Cloud provider or hardware configuration: GCP

Additional context

Add any other context about the problem here.

[mkuratczyk]

1. RabbitMQ 3.10 has been out of support for a long time
2. Why would you want to replace the current preStop hook with a sleep?

[nenych]

1. It does not matter what version of RabbitMQ, this change is about the operator.
2. For example give some time to the proxy to be able to stop traffic completely.

[mkuratczyk]

The reason it doesn't work is that Kubernetes doesn't allow multiple preStop hooks and currently the override adds the second hook (sleep) on top of the default one (exec) because it has a different YAML path (spec.containers[0].lifecycle.preStop.sleep and not spec.containers[0].lifecycle.preStop.exec). It's basically the same issue we had with readinessProbes: #1776.

This would be a somewhat risky feature, since using a sleep hook would silently turn off the default exec hook, which makes sure quorum queues are in a good state before proceeding with the shutdown.

@Zerpet any thoughts on whether we should allow this?

[Zerpet]

The preStop hook we configure with the Operator is one of the main safety features to manage RabbitMQ in Kubernetes. Without a compelling use case, I'm not keen to introduce a change to facilite the addition of pre stop hooks in override.

[nenych]

I understand, thank you so much for the explanation.