Kubernetes - Blue/Green Deployment

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This deployment is widely used across the companies. Its based on ACTIVE/PASSIVE concept.

We are going to create a deployment with the image - rajasekar/node-web-v1 of 3 replicas and bind to a service IP.

Next, We are going to create another deployment with the image rajasekar/node-web-v2 and enable this deployment in the service IP - aka IP cutover.

Make a note of the labels I am using in the deployment: app: nodejs and version: "1.0"


apiVersion: apps/v1

kind: Deployment

metadata:

  name: node-app-v1

  labels:

    app: node-app

spec:

  replicas: 3

  selector:

    matchLabels:

      app: nodejs

      version: "1.0"

  template:

    metadata:

      labels:

        app: nodejs

        version: "1.0"

    spec:

      containers:

      - name: nodejs-v1

        image: rajasekar/node-web-v1:latest

        imagePullPolicy: Never

        ports:

        - containerPort: 8080


root@masterk8s:/kube# kubectl get pods

NAME                           READY   STATUS    RESTARTS   AGE

node-app-v1-66945646db-9q78p   1/1     Running   0          69s

node-app-v1-66945646db-lh5q6   1/1     Running   0          69s

node-app-v1-66945646db-qvkp4   1/1     Running   0          69s

root@masterk8s:/kube#


Lets bind a service IP of type NodePort to it.


root@masterk8s:/kube# kubectl expose deployment node-app-v1 --type NodePort --port 8080 --target-port 8080 --name node-svc

service/node-svc exposed

root@masterk8s:/kube#


root@masterk8s:/kube# kubectl describe svc node-svc

Name:                     node-svc

Namespace:                default

Labels:                   app=node-app

Annotations:              <none>

Selector:                 app=nodejs,version=1.0

Type:                     NodePort

IP Family Policy:         SingleStack

IP Families:              IPv4

IP:                       10.99.189.136

IPs:                      10.99.189.136

Port:                     <unset>  8080/TCP

TargetPort:               8080/TCP

NodePort:                 <unset>  30080/TCP

Endpoints:                10.244.1.25:8080,10.244.1.26:8080,10.244.1.27:8080

Session Affinity:         None

External Traffic Policy:  Cluster

Events:                   <none>

root@masterk8s:/kube#


Lets test the endpoint:


root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v1-66945646db-lh5q6

root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v1-66945646db-9q78p

root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v1-66945646db-qvkp4

root@masterk8s:/kube# 


Now, Lets move on to GREEN deployment with the image: rajasekar/node-web-v2.

Here I have changed the version to 2.0 and referring to new image.


apiVersion: apps/v1

kind: Deployment

metadata:

  name: node-app

spec:

  replicas: 3

  selector:

    matchLabels:

      app: nodejs

  template:

    metadata:

      labels:

        app: nodejs

        version: "2.0"

    spec:

      containers:

      - name: nodejs-v2

        image: rajasekar/node-web-v2:latest

        imagePullPolicy: Never

        ports:

        - containerPort: 8080


root@masterk8s:/kube# kubectl get pods

NAME                           READY   STATUS    RESTARTS   AGE

node-app-v1-66945646db-9q78p   1/1     Running   0          4m19s

node-app-v1-66945646db-lh5q6   1/1     Running   0          4m19s

node-app-v1-66945646db-qvkp4   1/1     Running   0          4m19s

node-app-v2-78c686cc57-bm287   1/1     Running   0          4s

node-app-v2-78c686cc57-q2wpt   1/1     Running   0          4s

node-app-v2-78c686cc57-q68dv   1/1     Running   0          4s

root@masterk8s:/kube#


root@masterk8s:/kube# kubectl get deployment

NAME          READY   UP-TO-DATE   AVAILABLE   AGE

node-app-v1   3/3     3            3           4m33s

node-app-v2   3/3     3            3           18s

root@masterk8s:/kube#


root@masterk8s:/kube# kubectl describe deployment node-app-v1 | grep -i selector

Selector:               app=nodejs,version=1.0

root@masterk8s:/kube# kubectl describe deployment node-app-v2 | grep -i selector

Selector:               app=nodejs,version=2.0

root@masterk8s:/kube#


Now, Lets to the cutover.


root@masterk8s:/kube# kubectl patch service node-svc -p '{"spec": {"selector":{"version":"2.0"}}}'

service/node-svc patched

root@masterk8s:/kube# kubectl get ep

NAME         ENDPOINTS                                            AGE

kubernetes   192.168.45.128:6443                                  23h

node-svc     10.244.1.28:8080,10.244.1.29:8080,10.244.1.30:8080   5m46s

root@masterk8s:/kube#


Lets to curl:


root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v2-78c686cc57-q68dvThis is a secure link of version 99.99%

root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v2-78c686cc57-q2wptThis is a secure link of version 99.99%

root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v2-78c686cc57-q2wptThis is a secure link of version 99.99%

root@masterk8s:/kube# curl 10.99.189.136:8080

You've hit node-app-v2-78c686cc57-bm287This is a secure link of version 99.99%

root@masterk8s:/kube#


Nice. We have successfully did a cutover. If anything happens with the new code, then edit the service pointing to version 1.0.

If all works fine. Then scale down Version1.0 deployment and delete it.


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