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Kubernetes Services

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In this section we will take a look at services in kubernetes

Services

• Kubernetes Services enables communication between various components within and outside of the application.

  

Let’s look at some other aspects of networking

External Communication

• How do we as an external user access the web page?

  • From the node (Able to reach the application as expected)

    

  • From outside world (This should be our expectation, without something in the middle it will not reach the application)

    

## Service Types

#### There are 3 types of service types in kubernetes

1. NodePort
   • Where the service makes an internal port accessible on a port on the NODE. ``` apiVersion: v1 kind: Service metadata: name: myapp-service spec: types: NodePort ports:
     • targetPort: 80 port: 80 nodePort: 30008 ```

     To connect the service to the pod

     apiVersion: v1
     kind: Service
     metadata:
      name: myapp-service
     spec:
      type: NodePort
      ports:
      - targetPort: 80
        port: 80
        nodePort: 30008
      selector:
        app: myapp
        type: front-end
     

   

   #### To create the service

     $ kubectl create -f service-definition.yaml
   

   #### To list the services

     $ kubectl get services
   

   #### To access the application from CLI instead of web browser

     $ curl http://192.168.1.2:30008
   

   

   #### A service with multiple pods

   

   #### When Pods are distributed across multiple nodes

   

2. ClusterIP
   • In this case the service creates a Virtual IP inside the cluster to enable communication between different services such as a set of frontend servers to a set of backend servers.
3. LoadBalancer
   • Where the service provisions a loadbalancer for our application in supported cloud providers.

K8s Reference Docs:

• https://kubernetes.io/docs/concepts/services-networking/service/
• https://kubernetes.io/docs/tutorials/kubernetes-basics/expose/expose-intro/