prometheus adapter configmap:

apiVersion: v1
data:
  config.yaml: |
    rules:
    - metricsQuery: sum(<<.Series>>{<<.LabelMatchers>>}) by (<<.GroupBy>>)
      resources:
        overrides:
          kubernetes_namespace:
            resource: namespace
          queue:
            resource: service
      seriesQuery: rabbitmq_queue_messages{kubernetes_namespace!="",queue!=""}
kind: ConfigMap
metadata:
  annotations:
    meta.helm.sh/release-name: prometheus-adapter
    meta.helm.sh/release-namespace: default
  creationTimestamp: "2024-07-01T10:14:16Z"
  labels:
    app.kubernetes.io/component: metrics
    app.kubernetes.io/instance: prometheus-adapter
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: prometheus-adapter
    app.kubernetes.io/part-of: prometheus-adapter
    app.kubernetes.io/version: v0.11.2
    helm.sh/chart: prometheus-adapter-4.10.0
  name: prometheus-adapter
  namespace: default
  resourceVersion: "388932978"
  uid: f9dd9c27-d2e3-4b94-8c69-263a830bfd3c

Response of kubectl get –raw “/apis/custom.metrics.k8s.io/v1beta1”

{
  "kind": "APIResourceList",
  "apiVersion": "v1",
  "groupVersion": "custom.metrics.k8s.io/v1beta1",
  "resources": []
}

Document followed:
https://github.com/kubernetes-sigs/prometheus-adapter/ (Helm3)

Wanted to scale consumer pods on the basis of rabbitmq messages.

Rabbitmq Prometheus UI:
prometheus query