Agfdhyk

Scenario:
I have 2 clusters: A and B both with istio installed. I want to expose service-1 in cluster A as service-1.suffix, and let service-2 in cluster B access service-1 by: service-1.suffix. The folloing picture illustrates my idea.

In cluster A, I define a virtualService and Gateway to route the requests to service-1.

Gateway:

apiVersion: networking.istio.io/v1alpha3

kind: Gateway

metadata:

  name: service-1

spec:

  selector:

    istio: ingressgateway # use istio default ingress gateway

  servers:

  - port:

      number: 80

      name: http

      protocol: HTTP

    hosts:

    - "service-1.suffix"

VirtualService:

apiVersion: networking.istio.io/v1alpha3

kind: VirtualService

metadata:

  name: service-1

spec:

  hosts:

  - service-1.default.svc.cluster.local

  - "service-1.suffix"

  gateways:

  - service-1

  - mesh

  http:

  - route:

    - destination:

        host: service-1.default.svc.cluster.local

        port:

          number: 8080

This is working fine as I can use curl to access it successfully.

curl -I -HHost:service-1.suffix http://cluster_A_proxy:31380

The next step is creating Egress and VirtualService in Cluster B. Here are my definition files:

ServiceEntry:

apiVersion: networking.istio.io/v1alpha3

kind: ServiceEntry

metadata:

  name: service-1

spec:

  hosts:

  - "service-1.suffix"   #the global suffix mcm.com could be defined in mcm.

  #addresses:

  #- xxx/32

  ports:

  - number: 80   

    name: http

    protocol: HTTP

  resolution: STATIC

  location: MESH_EXTERNAL

  endpoints:

  - address: 1.1.1.1  #The cluster A proxy ip

    ports:

      http: 31380

VirtualService:

apiVersion: networking.istio.io/v1alpha3

kind: VirtualService

metadata:

  name: service-1

spec:

  hosts:

  - "service-1.suffix"

  http:

  - route:

    - destination:

        host: "service-1.suffix"

        port:

          number: 80

In Cluster B, when I try to use curl to resolve service-1.suffix, I got a DNS error saying this cannot be resolved.

curl: (6) Could not resolve host: service-1.suffix

How can I fix this?

#The command I am using in an istio app in Cluster B:

kubectl exec -it pod_name -c container_name bash

curl -I -HHost:service-1.suffix http://service-1.suffix

Edit:
When I use another resolvable hostname like www.google.com in serviceentry I can get it through, the requests to www.google.com will be redirected to service-1 in cluster A. Just the same, if I use nip.io as my suffix, it works well. However, the made up name service-1.suffix could not be resolved.

Define a Kubernetes ExternalName service with a random IP:

kind: Service

apiVersion: v1

metadata:

  name: service1

spec:

  type: ExternalName

  externalName: 1.1.1.1