Services in Kubernetes

In Kubernetes, Services are objects that provide stable network identities to Pods and abstract away the details of Pod IP addresses. Services allow Pods to receive traffic from other Pods, Services, and external clients.

There are four types of service in Kubernetes for exposing the network application that is running as one or more Pods in your cluster:

1. NordPort

2. ClusterIP

3. LoadBalancer

4. ExtrernalName

In this blog, the first three would be discussed with examples/tutorials.

Before we begin, my deployment file creates a Todo web app and I already have created a namespace called "django-todo-ns". The file is as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: django-todo-deploy
  labels:
    app: django-todo
  namespace: django-todo-ns
spec:
  replicas: 1
  selector:
    matchLabels:
      app: django-todo
  template:
    metadata:
      labels:
        app: django-todo
    spec:
      containers:
        - name: django-todo-app
          image: neelsoni26/django-todo-app
          ports:
            - containerPort: 8001

Let's start with NordPort

NordPort

Exposes the Service on each Node's IP at a static port (the NodePort).

Example: Create a Service for Deployment

apiVersion: v1
kind: Service
metadata:
  name: django-todo-nodeport
spec:
  type: NodePort
  selector:
    app: django-todo
  ports:
    - port: 8001
      targetPort: 8001
      nodePort: 30070

After creating the file, write the command:

kubectl apply -f service.yml

To verify this, get services with a specific namespace.

kubectl get service -n=django-todo-ns

To verify further, get URL and check.

minikube service django-todo-nodeport -n=django-todo-ns --url

Now hit this URL with curl.

curl -L http://192.168.49.2:30070

can also try in the browser:

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ClusterIP

For creating ClusterIP Service, I have created a config file:

apiVersion: v1
kind: Service
metadata:
  name: django-todo-clusterip
  namespace: django-todo-ns
spec:
  selector:
    app: django-todo
  type: ClusterIP
  ports:
    - port: 8001
      targetPort: 8001

Now, apply the config and check whether it is working or not.

kubectl apply -f clusterip-service.yml

kubectl get services -n=django-todo-ns

For further verification, get the pod list and execute it. Then access the URL for ClusterIP.

kubectl get pods -n=django-todo-ns

kubectl exec django-todo-deploy-77485cfcbd-mjjk2 -it -n=django-todo-ns bash

curl -L 10.111.162.46:8001

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LoadBalancer

To create LoadBalancer Service, create a config file for it with the type: LoadBalancer

apiVersion: v1
kind: Service
metadata:
  name: django-todo-loadbalancer
  namespace: django-todo-ns
spec:
  selector:
    app: django-todo
  ports:
    - port: 8001
      targetPort: 8001
  type: LoadBalancer

Next, apply the file and verify by get service.

kubectl apply -f loadbalancer-service.yml

kubectl get services -n=django-todo-ns

There will be pending written in the external IP section for LoadBalancer. To get the IP, write the below-given command, it will return an IP address of your application with LoadBalancer service.

minikube service django-todo-loadbalancer -n=django-todo-ns --url

You may write minikube service list for a list of services with name, namespace, port and URL.

You can copy and access the URL in your browser:

Or verify by curl -L <IP>:<Port>

If you get this code, then your app is working correctly with the Service.

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Thank You.