19-Services.md

Kubernetes Services

• Take me to Video Tutorial

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 POD accessible on a POD 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/