For the past week i've been trying to set up the sock-shop demo application together with Istio in Google's Kubernetes Engine. However, when i curl to my ingress-gateway's External IP-adress with curl -I http://${GATEWAY_URL}/ (where ${GATEWAY_URL} corresponds to the external IP i receive when i run kubectl get service istio-ingressgateway -n istio-system), i get this as a response:

HTTP/1.1 503 Service Unavailable
date: Mon, 22 Jul 2019 13:50:11 GMT
server: envoy
transfer-encoding: chunked

The output of kubectl logs -n istio-system istio-ingressgateway-64d6cfc6cb-m4sbx is as follows:

[2019-07-22T13:50:12.021Z] "HEAD /HTTP/1.1" 503 NR 0 0 2 - "10.132.0.4" "curl/7.52.1" "25ea898e-0f51-4997-b3bc-a08f586dcf8a" "35.240.37.125" "-" - - 10.4.0.4:80 10.132.0.4:52250

I use the following deployment for the sock-shop (it's basically the traditional sock-shop, except i've added the http--prefix to service ports that listen on port 80):

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: carts-db
  labels:
    name: carts-db
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: carts-db
    spec:
      containers:
      - name: carts-db
        image: mongo
        ports:
        - name: mongo
          containerPort: 27017
        securityContext:
          capabilities:
            drop:
              - all
            add:
              - CHOWN
              - SETGID
              - SETUID
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: carts-db
  labels:
    name: carts-db
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 27017
    targetPort: 27017
  selector:
    name: carts-db
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: carts
  labels:
    name: carts
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: carts
    spec:
      containers:
      - name: carts
        image: weaveworksdemos/carts:0.4.8
        ports:
         - containerPort: 80
        env:
         - name: ZIPKIN
           value: zipkin.jaeger.svc.cluster.local
         - name: JAVA_OPTS
           value: -Xms64m -Xmx128m -XX:PermSize=32m -XX:MaxPermSize=64m -XX:+UseG1GC -Djava.security.egd=file:/dev/urandom
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: carts
  labels:
    name: carts
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-carts
  selector:
    name: carts
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: catalogue-db
  labels:
    name: catalogue-db
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: catalogue-db
    spec:
      containers:
      - name: catalogue-db
        image: weaveworksdemos/catalogue-db:0.3.0
        env:
          - name: MYSQL_ROOT_PASSWORD
            value: fake_password
          - name: MYSQL_DATABASE
            value: socksdb
        ports:
        - name: mysql
          containerPort: 3306
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: catalogue-db
  labels:
    name: catalogue-db
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 3306
    targetPort: 3306
    name: mysql-catalogue-db
  selector:
    name: catalogue-db
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: catalogue
  labels:
    name: catalogue
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: catalogue
    spec:
      containers:
      - name: catalogue
        image: weaveworksdemos/catalogue:0.3.5
        ports:
        - containerPort: 80
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: catalogue
  labels:
    name: catalogue
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-catalogue
  selector:
    name: catalogue
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: front-end
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: front-end
    spec:
      containers:
      - name: front-end
        image: weaveworksdemos/front-end:0.3.12
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
        ports:
        - containerPort: 8079
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
          readOnlyRootFilesystem: true
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: front-end
  labels:
    name: front-end
  namespace: sock-shop
spec:
  type: NodePort
  ports:
  - port: 80
    targetPort: 8079
    nodePort: 30001
    name: http-frontend
  selector:
    name: front-end
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: orders-db
  labels:
    name: orders-db
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: orders-db
    spec:
      containers:
      - name: orders-db
        image: mongo
        ports:
        - name: mongo
          containerPort: 27017
        securityContext:
          capabilities:
            drop:
              - all
            add:
              - CHOWN
              - SETGID
              - SETUID
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: orders-db
  labels:
    name: orders-db
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 27017
    targetPort: 27017
  selector:
    name: orders-db
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: orders
  labels:
    name: orders
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: orders
    spec:
      containers:
      - name: orders
        image: weaveworksdemos/orders:0.4.7
        env:
         - name: ZIPKIN
           value: zipkin.jaeger.svc.cluster.local
         - name: JAVA_OPTS
           value: -Xms64m -Xmx128m -XX:PermSize=32m -XX:MaxPermSize=64m -XX:+UseG1GC -Djava.security.egd=file:/dev/urandom
        ports:
        - containerPort: 80
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: orders
  labels:
    name: orders
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-orders
  selector:
    name: orders
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: payment
  labels:
    name: payment
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: payment
    spec:
      containers:
      - name: payment
        image: weaveworksdemos/payment:0.4.3
        ports:
        - containerPort: 80
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: payment
  labels:
    name: payment
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-payment
  selector:
    name: payment
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: queue-master
  labels:
    name: queue-master
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: queue-master
    spec:
      containers:
      - name: queue-master
        image: weaveworksdemos/queue-master:0.3.1
        ports:
        - containerPort: 80
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: queue-master
  labels:
    name: queue-master
  annotations:
    prometheus.io/path: "/prometheus"
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-queue-master
  selector:
    name: queue-master
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: rabbitmq
  labels:
    name: rabbitmq
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: rabbitmq
    spec:
      containers:
      - name: rabbitmq
        image: rabbitmq:3.6.8
        ports:
        - containerPort: 5672
        securityContext:
          capabilities:
            drop:
              - all
            add:
              - CHOWN
              - SETGID
              - SETUID
              - DAC_OVERRIDE
          readOnlyRootFilesystem: true
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: rabbitmq
  labels:
    name: rabbitmq
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 5672
    targetPort: 5672
  selector:
    name: rabbitmq
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: shipping
  labels:
    name: shipping
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: shipping
    spec:
      containers:
      - name: shipping
        image: weaveworksdemos/shipping:0.4.8
        env:
         - name: ZIPKIN
           value: zipkin.jaeger.svc.cluster.local
         - name: JAVA_OPTS
           value: -Xms64m -Xmx128m -XX:PermSize=32m -XX:MaxPermSize=64m -XX:+UseG1GC -Djava.security.egd=file:/dev/urandom
        ports:
        - containerPort: 80
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: shipping
  labels:
    name: shipping
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-shipping
  selector:
    name: shipping
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: user-db
  labels:
    name: user-db
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: user-db
    spec:
      containers:
      - name: user-db
        image: weaveworksdemos/user-db:0.4.0
        ports:
        - name: mongo
          containerPort: 27017
        securityContext:
          capabilities:
            drop:
              - all
            add:
              - CHOWN
              - SETGID
              - SETUID
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /tmp
          name: tmp-volume
      volumes:
        - name: tmp-volume
          emptyDir:
            medium: Memory
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: user-db
  labels:
    name: user-db
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 27017
    targetPort: 27017
  selector:
    name: user-db
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: user
  labels:
    name: user
  namespace: sock-shop
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: user
    spec:
      containers:
      - name: user
        image: weaveworksdemos/user:0.4.7
        ports:
        - containerPort: 80
        env:
        - name: MONGO_HOST
          value: user-db:27017
        securityContext:
          runAsNonRoot: true
          runAsUser: 10001
          capabilities:
            drop:
              - all
            add:
              - NET_BIND_SERVICE
          readOnlyRootFilesystem: true
      nodeSelector:
        beta.kubernetes.io/os: linux
---
apiVersion: v1
kind: Service
metadata:
  name: user
  labels:
    name: user
  namespace: sock-shop
spec:
  ports:
    # the port that this service should serve on
  - port: 80
    targetPort: 80
    name: http-user
  selector:
    name: user

with the following gateway gateway.yaml...

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: gateway
spec:
  selector:
    istio: ingressgateway
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "*"

and the virtualservice virtual.yaml:

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: external-services
spec:
  hosts:
  - "*"
  gateways:
  - gateway                      # 1
  http:
  - route:
    - destination:
        host: front-end             # 2
        port:
          number: 80

I'm at a loss as to what could be the cause for the 503 error that's previously mentioned. The output of the logs states 'NR', which indicates that it's found no applicable route, but that's what the virtualservice is for, so i think that's where i made a mistake, but i can't figure out what exactly it is.