shreyank031 / k8s-rollingupdate-horizontalpodautoscale

This repository contains a Kubernetes Deployment manifest for deploying an application with rolling update and horizontal pod autoscaller

Nginx Deployment with Rolling Update

This repository contains a Kubernetes Deployment manifest for deploying an Nginx web server with a rolling update strategy.

Table of Contents

• Overview
• Prerequisites
• Deployment
• Rolling Update

Overview

The env-deployment.yaml file defines a Kubernetes Deployment resource that deploys four replicas of an Nginx web server. The Deployment uses a rolling update strategy to ensure zero downtime during updates.

Prerequisites

Before deploying the Nginx application, ensure that you have the following prerequisites:

• A Kubernetes cluster up and running
• The kubectl command-line tool installed and configured to communicate with the cluster

Deployment

To deploy the Nginx application, follow these steps:

1. Apply the Deployment manifest:

kubectl apply -f env-deployment.yaml

The above command will create the Deployment resource and spin up four replicas of the Nginx Pods.

2. Verify that the Deployment and Pods are running:

kubectl get deployment env-deployment
kubectl get pods

You should see the env-deployment Deployment and four Nginx Pods in the running state.

Demo

Rolling Update

The env-deployment.yaml manifest defines a rolling update strategy for the Deployment. When you update the Deployment, such as changing the Nginx image version or modifying the container configuration, Kubernetes will perform a rolling update without causing any downtime.

Here are the key parameters defined for the rolling update strategy:

• maxSurge: 1 : Allows one extra Pod to be created during the update process. The new ReplicaSet is created with one extra Pod running updated nginx:1.17 image. The original ReplicaSet will be as it is running 4 pods with nginx:1.16 version. Totally 5 pods with 1 updated image and 4 with old image

  

• maxUnavailable: 0 : Ensures that all Pods are available during the update process. Assume if 3 pods are running out of 4 pods (the desired number of replicas), then k8s won't update. It's typically 4 - 0 = 4 where all the 4 pods should be up and running.

• minReadySeconds: 10 : Specifies that a new Pod should be ready for at least 10 seconds before considering it available. Then only the one of the pod in original ReplicaSet will be deleted automatically. Suppose if the pod is not running as expected in newly created ReplicaSet, then k8s waits for 10, checks in again waits, doesn't udpate if the pod is not running with new image.

At the end when all the pods are updated in the new ReplicaSet, the last remaining pod inside old/original Replicaset will be terminated

Don't forget to see Horizontal Pod Autoscaller here