Services in Kubernetes

• Used to access the Kubernetes Pods

Cluster-IP Service

• It is used to the enable the communication between the pods within the cluster.

Node-Port Service

• It is used to expose the pod to the internet.

• Uses the port range : 3000 - 32767

• Created for each micro service / Application Layer

Load Balancer Service

• Is used to reduce the number of IPs address to be maintained for NodePort Service.

• Load Balancer Service Created on top of the NodePort Service, will receives the request from end user through internet and Route the request to the corresponding nodeport service and access the pod within that.

• Load Balancer Service will be created at the Application Level.

Ingress Controller Service

• Is used to reduce the Load-Balancer Service and map the services to Load-Balancer

Let’s create a NodePort Service

• Create Deployment file

  •   apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: my-node-app
      spec:
        replicas: 3
        selector:
          matchLabels:
            app: my-node-app
        template:
          metadata:
            labels:
              app: my-node-app
          spec:
            containers:
            - name: my-node-app
              image: jayk2810/mynodeimg:v1
              ports:
              - containerPort: 3000
    

• Create Service YAML file

  •   apiVersion: v1
      kind: Service
      metadata:
        name: my-service
      spec:
        type: NodePort
        selector:
          app: my-node-app
        ports:
          - port: 80
            targetPort: 3000
            nodePort: 30028
    

• Access the deployment from browser using public ip of the instance with nodeport

  • 

Kubernetes Host Path Volume

• Maintain Persistant Data

• Hostpath Volume is created at the pods level. Not at the Container level.

•   apiVersion: v1
    kind: Pod
    metadata:
      name: nginx-hostpath
    spec:
      containers:
        - name: nginx-container
          image: nginx
          volumeMounts:
          - mountPath: /test-mnt
            name: test-vol
      volumes:
      - name: test-vol
        hostPath:
          path: /test-vol
  

• Create and Display HostPath

  •   kubectl create -f nginx-hostpath.yaml
      kubectl get po
      kubectl exec nginx-hostpath df /test-mnt
    

• Master node

  • 

• Worker node

  • 

Namespaces

• Logical Partition of the Kubernetes Cluster.

• This will create an isolated path for deployments

• Namespaces can be created based on the Environments/Teams