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Networking

Networking#

In this section we'll see how OSToy uses intra-cluster networking to separate functions by using microservices and visualize the scaling of pods.

Let's review how this application is set up...

OSToy Diagram

As can be seen in the image above, we have defined at least 2 separate pods, each with its own service. One is the frontend web application (with a service and a publicly accessible route) and the other is the backend microservice with a service object so that the frontend pod can communicate with the microservice (across the pods if more than one). Therefore this microservice is not accessible from outside this cluster, nor from other namespaces/projects (due to OpenShift's network policy, ovs-networkpolicy). The sole purpose of this microservice is to serve internal web requests and return a JSON object containing the current hostname (which is the podname) and a randomly generated color string. This color string is used to display a box with that color displayed in the tile titled "Intra-cluster Communication".

Networking#

1. Intra-cluster networking#

Click on Networking in the left menu. Review the networking configuration. The right tile titled "Hostname Lookup" illustrates how the service name created for a pod can be used to translate into an internal ClusterIP address.

2. Lookup internal IP address of the service#

Enter the name of the microservice we created in the right tile ("Hostname Lookup") following the format of my-svc.my-namespace.svc.cluster.local which we created in the service definition of ostoy-microservice.yaml which can be seen here:

apiVersion: v1
kind: Service
metadata:
  name: ostoy-microservice-svc
  labels:
    app: ostoy-microservice
spec:
  type: ClusterIP
  ports:
    - port: 8080
      targetPort: 8080
      protocol: TCP
  selector:
    app: ostoy-microservice

In this case we will enter: ostoy-microservice-svc.ostoy.svc.cluster.local

3. IP address returned#

We will see an IP address returned. In our example it is 172.30.165.246. This is the intra-cluster IP address; only accessible from within the cluster.

ostoy DNS