I have a number of restful services within our system

• Some are our within the kubernetes cluster
• Others are on legacy infrasture and are hosted on VM's

Many of our restful services make synchronous calls to each other (so not asynchronously using message queues)

We also have a number of UI's (fat clients or web apps) that make use of these services

We might define a simple k8s manifest file like this 1. Pod 2. Service 3. Ingress

apiVersion: v1
kind: Pod
metadata:
  name: "orderManager"
spec:
  containers:
    - name: "orderManager"
      image: "gitlab-prem.com:5050/image-repo/orderManager:orderManager_1.10.22"
---
apiVersion: v1
kind: Service
metadata:
  name: "orderManager-service"
spec:
  type: NodePort
  selector:
    app: "orderManager"
  ports:
    - protocol: TCP
      port: 50588
      targetPort: 50588
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: orderManager-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
    - http:
        paths:
          - path: /orders
            pathType: Prefix
            backend:
              service:
                name: "orderManager-service"
                port:
                  number: 50588

I am really not sure what the best way for restful services on the cluster to talk to each other.

• It seems like there is only one good route for callers outside the cluster which is use the url built by the ingress rule
• Two options within the cluster

This might illustrate it further with an example

I write cluster ip a few times above but in real life we put something top so there is a friendly name like http://mycluster/orders

So when caller and reciever are both on cluster is it either

• Use the ingress rule which is also used by services and apps outside the cluster
• Use the nodeport service name which is used in the ingress rule
• Or perhaps something else!

One benefit of using nodeport service name is that you do not have to change your base URL.

• The ingress rule appends an extra elements to the route (in the above case orders)
• When I move a restful service from legacy to k8s cluster it will increase the complexity