Knative/Istio with AWS Application Load Balancers

[Matteo Dipirro]

Hello Community!

I have a question regarding the interaction between Knative serving, Istio, and AWS Application Load Balancers (ALB from now on).

I'm deploying Knative Serving v0.20 using the YAML manifests (not the kn console) and Istio using the Helm charts. Also, I've been following some online guides (here and here) to have Istio use an ALB instead of creating an ELB. According to them, the major configuration change needed to have Istio use the ALB is gateways.istio-ingressgateway.type=NodePort. That change makes Istio not create its load balancer. 

However, I noticed that, when Istio does not create the load balancer, Kubernetes won't let me delete the Knative ingress (attached to this question). I believe the main reason is the finalizers section. As a matter of fact, if I modify the resource in the cluster, replacing

finalizers:

  - ingresses.networking.internal.knative.dev

with finalizers: [] then Kubernetes lets me destroy it. I searched for an explanation in the documentation and online, but haven't found any. At first, I thought I was messing up with the AWS ALB controller, so I tried to change Istio's configuration without creating any ALBs but the issue wouldn't disappear.

Could you explain what that Ingress is used for and how can I solve (or, at least, work around) this issue? Pointers to relevant discussions/examples/docs are welcome as well!

Thank you so much!