Kubernetes Istio exposure not working with Virtualservice and Gateway - kubernetes

Question

So we have the following use case running on Istio 1.8.2/Kubernetes 1.18:
Our cluster is exposed via a External Loadbalancer on Azure. When we expose the app the following way, it works:
---
apiVersion: apps/v1
kind: ReplicaSet
metadata:
annotations:
...
name: frontend
namespace: frontend
spec:
replicas: 1
selector:
matchLabels:
app: applicationname
template:
metadata:
labels:
app: appname
name: frontend
customer: customername
spec:
imagePullSecrets:
- name: yadayada
containers:
- name: frontend
image: yadayada
imagePullPolicy: Always
ports:
- name: https
protocol: TCP
containerPort: 80
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
---
apiVersion: v1
kind: Service
metadata:
name: frontend-svc
namespace: frontend
labels:
name: frontend-svc
customer: customername
spec:
type: LoadBalancer
ports:
- name: http
port: 80
targetPort: 80
selector:
name: frontend
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: frontend
namespace: frontend
annotations:
kubernetes.io/ingress.class: istio
kubernetes.io/tls-acme: "true"
cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
rules:
- host: "customer.domain.com"
http:
paths:
- path: /
pathType: Prefix
backend:
serviceName: frontend-svc
servicePort: 80
tls:
- hosts:
- "customer.domain.com"
secretName: certificate
When we start using a Virtualservice and Gateway, we fail to make it work for some reason. We wanna use VSVC and Gateways cause they offer more flexibility and options (like url rewriting). Other apps dont have this issue running on istio (much simpler as well), we dont have networkpolicy in place (yet). We simply cannot reach the webpage. Anyone has an idea? Virtualservice and Gateway down below. with the other 2 replicasets not mentioned cause they are not the problem:
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
creationTimestamp: null
name: virtualservice-name
namespace: frontend
spec:
gateways:
- frontend
hosts:
- customer.domain.com
http:
- match:
- uri:
prefix: /
route:
- destination:
host: frontend
port:
number: 80
weight: 100
- match:
- uri:
prefix: /api/
route:
- destination:
host: backend
port:
number: 8080
weight: 100
- match:
- uri:
prefix: /auth/
route:
- destination:
host: keycloak
port:
number: 8080
weight: 100
---
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: frontend
namespace: frontend
spec:
selector:
istio: ingressgateway # use istio default controller
servers:
- port:
number: 80
name: http2
protocol: HTTP
tls:
httpsRedirect: True
hosts:
- "customer.domain.com"
- port:
number: 443
name: https
protocol: HTTPS
tls:
mode: PASSTHROUGH
credentialName: customer-cert
hosts:
- "customer.domain.com"

Answer 1

Your Gateway specifies PASSTHROUGH, however your VirtualService provides an HttpRoute. This means the TLS connection is not terminated by the Gateway, but the VirtualService expects terminated TLS. See also this somewhat similar question.
How do I properly HTTPS secure an application when using Istio?

Answer 2

#user140547 Correct, we changed that now. But we still couldn't access the application.
We found out that one of the important services was not receiving gateway traffic, since that one wasn't setup correctly. It is our first time having an istio deployment with multiple services. So we thought each of them needed their own Gateway. Little did we know that 1 gateway was more then enough...