Deploying an Application on Kubernetes.

Introduction
Kubernetes is an open source technology used to autonomously deploy, scale, and manage applications that use containers. It is a popular container orchestration solution since it enables the control of several containers as a single entity as an alternative to managing each container separately.

This is a walkthrough of deploying an application to Azure Kubernetes Service similar to my previous article walkthrough.

What will be covered

• Azure Kubernetes Service
• Azure Container Registry
• Docker Container
• Azure CLI
• Kubectl
• Simple Node app

Overview
A note keeper app written in node js will be containerized and pushed to ACR, after which one Kubernetes cluster will be created on AKS and a deployment and a service will be created having 4 pod replicas via a manifest file.

Prerequisites

• Terminal and Azure CLI installed on local machine - some of the steps for this project (such as connecting to kubernetes cluster will be done using Azure CLI).
• Docker installed on local machine - which will be used to build an image and push to a registry (Azure Container Registry in this demo).
• Azure account with active subscription.
• Code Editor or IDE - which will be used to write code that will be containerized.
• Terraform installed - an IAC tool that will be used to provision infrastructure on Azure.

Note: The required services can be created using either terraform, Azure portal or Azure CLI.

Getting Started

• Testing sample app locally
  • Write the code or fork and clone app from Github
  • Navigate to application folder on terminal using cd <foldername>
  • Install dependencies using npm install
  • Run app to test using node <filename> or npm <filename>

• Login to azure using az login on terminal.

• Provision infrastructure on Azure with terraform using the following commands: terraform init terraform fmt terraform validate terraform plan terraform apply(note that a terraform file has a .tf extension)

Head to azure portal to confirm if infrastructure is provisioned

Containerize the application

• After resources have been provisioned on azure, we need to login to ACR using credentials (which includes login server, username and password) from container registry => settings => access keys

• Navigate to your project directory via terminal and login using the details from the step above docker login <login server> --username <username> --password <password>

• Build docker image using this command docker build -t <name>:<tag> . where . is the current directory.

• Check the image exists using docker images command ( this lists all available images, the first image is my newly created image).
• Push the image to ACR using docker push <name>:<tag>

• Going over to azure portal => container registry, to verify the push is successful.

• I created a container using my image (exercising how to forward ports, run container in a detached mode, give container a specified name and run the app using the forwarded port on my local machine)

Connect to Cluster

• kubectl will be used to manage the Kubernetes cluster. Run the command az aks get-credentials --resource-group <resourcegroupname> --name <clustername> to configure kubectl and connect to the cluster we previously created and also verify connection using kubectl get nodes to return a list of the cluster nodes.

• Kubernetes Deployment: A Deployment is one of the Kubernetes objects that is used to manage Pods via ReplicaSets in a declarative way. It provides updates, control as well as rollback functionalities. This deployment file will be used to:
• Create a deployment (which automatically creates a replicaset), service and pods.

• Lists all objects created at once using kubectl get command

• Get more details about the deployment, use kubectl describe deployments <deploymentname> command

• Scale down replica set from 2 to 4

• And also seeing the change in the events log

• Deleting a pod and showing how a deployment always ensures the desired number of pods is always present.

• Head to azure portal => kubernetes cluster => kubernetes resources => services and ingresses to view ports and pods.

• The app can be accessed using external IP of the service.

Challenges encountered during this project

• Creating a new azure account due to credit card issues
• I encountered the ImagePullBackOff and ErrImagePull error which was as a result of not properly connecting my azure container registry to my kubernetes cluster, this was detected while debugging .

• Changing my demo app from a note keeper app to a basic node app and back to my note keeper app due to ImagePullBackOff and ErrImagePull error.

Conclusion
This tutorial shows how to:

• Create a Docker image for a node application
• Push the image on ACR.
• Deploy on kubernetes

The End.

Thank you for reading