1. Proxy Service in Virtual Service:

   • Within the Istio virtual service definition, add a proxy service as a route destination.
   • Set the host of this proxy service to `keda-add-ons-http-interceptor-proxy`` (the KEDA HTTP Addon interceptor service).
   • Set the port to `8080`` (the default interceptor port).

Example yaml

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: example
  namespace: default
spec:
  http:
    - route:
        - destination:
            host: keda-add-ons-http-interceptor-proxy
            port: 8080

2. Namespace Alignment:

   • Ensure that both the KEDA HTTP Addon and the Istio virtual service are deployed within the same Kubernetes namespace. This ensures proper communication between the components.

• When a user makes a request, the Istio virtual service routes it to the KEDA HTTP Addon interceptor service.
• The interceptor service captures request metrics and relays them to the KEDA scaler component.
• Based on these metrics and scaling rules defined in the KEDA configuration, the KEDA scaler automatically scales the target workload (e.g., a deployment) up or down (including scaling to zero).

1. Error: context marked done while waiting for workload reach > 0 replicas

   • This error indicates that the KEDA_CONDITION_WAIT_TIMEOUT value (default: 20 seconds) might be too low. The workload scaling process may not be complete within this timeframe.
   • To increase the timeout:
     • If using Helm, adjust the `interceptor.replicas.waitTimeout`` parameter (see reference below).
     • Reference: https://github.com/kedacore/charts/blob/main/http-add-on/values.yaml#L139

2. 502 Errors with POST Requests:

   • You might encounter 502 errors during POST requests when the request is routed through the interceptor service. This could be due to insufficient timeout settings.
   • To adjust timeout parameters:
     • If using Helm, modify the following parameters (see reference below):
       • KEDA_HTTP_CONNECT_TIMEOUT
       • KEDA_RESPONSE_HEADER_TIMEOUT
       • KEDA_HTTP_EXPECT_CONTINUE_TIMEOUT
     • Reference: https://github.com/kedacore/charts/blob/main/http-add-on/values.yaml#L152

3. Immediate Scaling Down to Zero:

   • If minReplica is set to 0 in the HTTPScaledObject, the application will immediately scale down to 0.
   • There's currently no built-in mechanism to delay this initial scaling.
   • A PR is in progress to add this support: kedacore/keda#5478
   • As a workaround, keep minReplica initially as 1 and update it to 0 after the desired delay.

1. Service Setup in Front Door:

   • Set up Azure Front Door to route traffic to your AKS cluster.
   • Ensure that the Origin Host header matches the actual AKS host. Front Door enforces case-sensitive routing, so configure the Origin Host exactly as the AKS host name.

2. KEDA HTTP Add-on Integration:

   • Use an HTTPScaledObject to manage scaling based on incoming traffic.
   • Front Door should route traffic to the KEDA HTTP Add-on interceptor service in your AKS cluster.

3. Case-Sensitive Hostnames:

   • Be mindful that Azure Front Door treats the Origin Host header in a case-sensitive manner.
   • Ensure consistency between the AKS ingress hostname (e.g., foo.bar.com) and Front Door configuration.

• 404 Error for Hostnames with Different Case:
  • Requests routed with inconsistent casing (e.g., foo.Bar.com vs. foo.bar.com) will trigger 404 errors. Make sure the Origin Host header matches the AKS ingress host exactly.
  • If you encounter errors like PANIC=value method k8s.io/apimachinery/pkg/types.NamespacedName.MarshalLog called using nil *NamespacedName pointer, verify the Origin Host header configuration.

• Azure Front Door routes traffic to AKS based on a case-sensitive host header.
• The KEDA HTTP Add-on scales the workload in response to traffic, based on predefined scaling rules.