Prerequisites

Assuming that Kubernetes installation processes are done. Let's dive in:-

Commands used for running the Kubernetes practice

To get the namespaces that are existing.

kubectl get namespaces or kubectl get ns

kubectl get pods -ns=django-todo-ns  # To get the pods which are running under the namespace

For creating a namespace

kubectl create namespace django-todo-ns
kubectl get ns

Create a directory for Kubernetes

mkdir deploy_k8s
cd deploy_k8s/

Writing configurations for POD.yml

Please refer to https://kubernetes.io/ always for the latest configurations.

Create pod.yml

vim pod.yml

apiVersion: v1

kind: Pod

metadata:

  name: django-todo
  namespace: django-todo-ns
spec:

  containers:

  - name: django-todo

    image: ashwathy/django-todo-app:latest //image should be pushed to                  dockerhub

    ports:

    - containerPort: 80

Here we need the image to be pushed to the docker hub too.

Now applying it.

kubectl apply -f pod.yml

Now go to the worker node

sudo su
docker ps

The pods will be running here.

In case you close the master node use the below command.

mkdir -p $HOME/.kube
sudo cp -i etc/kubernetes/admin.conf $HOME/.kube/configonfig
chown $(id -u):$(id -g) $HOME/.kube/configonfig
export KUBECONFIG=$HOME/.kube/config

In the worker node: The image is running.

sudo su
docker ps

cp pod.yml redit_pod.yml   #For reddit clone apps

AutoHealing process:-

Checking the pods running initially

kubectl get  pods -n=django-todo-ns

docker ps   #In worker node
docker kill <CONTAINERID> #Kill the container and it auto heals

Deleting PODS:-

kubectl delete -f pod.yml  #Deleting it in  master node

Replica Set/Scaling:-

To get a specific label from the selector we have to create a deployment file:-

vim deployment.yml

YAML fILE
piVersion: apps/v1

kind: Deployment

metadata:

  name: django-todo-deployment
  namespace: django-todo-ns

  labels:

    app: django-todo

spec:

  replicas: 3

  selector:

    matchLabels:

      app: django-todo

  template:

    metadata:

      labels:

        app: django-todo

    spec:

      containers:

      - name: django-todo

        image: trainwithshubham/django:latest

        ports:

        - containerPort: 8000

Apply the deployment file:-

kubectl apply -f deployment.yml

In worker node:- Four containers/pods are running

Checking in master node:-

kubectl get  pods -n=django-todo-ns or watch kubectl get  pods -n=django-todo-ns (It will reresh every 2 seconds)

kubectl get pods -o wide -n django-todo-ns  #For a wider view

Every pod is having Private IP. For accessing the specific pod we need to go to the specific IP and access the pods which is not possible. So we are interacting with the traffic using the service.yml which gives the label inside the deployment.yml the internet access. Service has 3 types:-

1. Give the internal IPs under the labels one port number so that service.yml can connect to it.

2)Cluster IP:- Assign the cluster IP and service.yml can access it.

3)Load Balancer:-According to the load it can access the pods inside the cluster.

Service.yml-

vim service.yml

apiVersion: v1
kind: Service
metadata:
  name: django-todo-service
  namespace: django-todo-ns
spec:
  type: NodePort
  selector:
    app: django-todo
  ports:
      # By default and for convenience, the `targetPort` is set to the same value as the `port` field.
    - port: 80  // We use the concept of port binding here where 80 will be mapped to 8000 target port and cluster Ip port will be 30007-80 is the host port(-p 80:8000)
      targetPort: 8000
      # Optional field
      # By default and for convenience, the Kubernetes control plane will allocate a port from a range (default: 30000-32767)
      nodePort: 30007

Apply the service:-

kubectl apply -f service.yml

kubectl get service

kubectl get service -n django-todo-ns

Apply the service

kubectl apply -f service.yml

Run the port in public ip:3007 and open the port in the worker node

We can change the scaling in replicas and do the deployment command again to scale it. We can use the below command to check all the scaling up and down, Strategy type can also be checked.

kubectl describe deployment.apps/django-todo-deployment -n django-todo-ns