RabbitMQ Scaler with env trigger authentication not working

[jackson-chris]

I'm trying to configure the RabbitMQ Scaler in an environment running Keda 2.11.x but the scaledobject is failing to become ready, when describing the scaled object I see:

  Warning  KEDAScalerFailed         2m40s (x19 over 24m)  keda-operator  error parsing rabbitmq metadata: no host setting given
  Warning  ScaledObjectCheckFailed  2m40s (x19 over 24m)  keda-operator  failed to ensure HPA is correctly created for ScaledObject

The configuration I am using is below:

  apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: foo
spec:
  env:
  - name: RABBITMQ_MANAGEMENT_URL
    parameter: host

and

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: foo
spec:
  advanced:
    horizontalPodAutoscalerConfig:
      behavior:
        scaleDown:
          policies:
          - periodSeconds: 15
            type: Percent
            value: 100
          stabilizationWindowSeconds: 60
        scaleUp:
          policies:
          - periodSeconds: 15
            type: Percent
            value: 100
          - periodSeconds: 15
            type: Pods
            value: 4
          selectPolicy: Max
          stabilizationWindowSeconds: 0
  cooldownPeriod: 120
  maxReplicaCount: 8
  minReplicaCount: 1
  pollingInterval: 15
  scaleTargetRef:
    name: foo
  triggers:
  - metadata:
      mode: QueueLength
      protocol: http
      queueName: merge
      value: "5"
    type: rabbitmq
  - authenticationRef:
      name: foo
    metadata:
      mode: MessageRate
      protocol: http
      queueName: merge
      value: "100"
    type: rabbitmq

Based upon what I read in the docs I assumed this should work since in the deployment I'm looking to scale I have an environment variable named RABBITMQ_MANAGEMENT_URL with the required host string for the scaler.

I know instead I can use:

  triggers:
  - metadata:
      hostFromEnv: RABBITMQ_MANAGEMENT_URL

when defining the ScaledObject and it becomes ready but I'm curious why my initial approach using TriggerAuthentication didn't work?

[jackson-chris]

I found my mistake in the fact that the authenticationRef needs to be defined for each trigger. It was missing in the QueueLength mode trigger.