K8s

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Introduction

This repo holds the manifest files for the K8s (1.22) cluster. There are 6 manifest files such that when you apply it on the K8s cluster it will produce below diagram. Note: there is a high-quality version of this figure (K8s-Diagram.pdf)

Key Features

The 6 YAML files are defined as below

1- client-depl

This file has the deployment code of the web app along with service code.

• The web app is written in typescript using react JS library.
• The docker container/Pod is exposed on port 3000.
• The pod is set for 1 replica.
• The pod request resources are memory: 200Mi and CPU: 100m.
• The service type is ClusterIP and exposes port 3000 of the Pod.

2- server-depl

This file has the deployment code of the backend server for the web app along with service code.

• The web app is written in NodeJS.
• The docker container/Pod is exposed on port 3000.
• The pod is set for 1 replica.
• The pod request resources are memory: 200Mi and CPU: 100m.
• The pod limit resources are 200Mi and CPU: 100m.
• The server pod takes the Mongo-URL from Secret.
• The service type is ClusterIP and exposes port 3000 of the Pod.

3- mongo-depl

This file has the deployment code of the Mongodb server along with service code.

• The docker container/Pod is exposed on port 27017.
• The pod is set for 1 replica.
• The server pod takes the Mongo-URL from Secret.
• The service type is ClusterIP and exposes port 27017 of the Pod.
• The pod uses Persistent Volume Claim (mongo-pvc) to store Mongodb data (/data/db).

4- mongo-secret

This file has the secret code of the Mongodb server by which the nodeJS server will use to connect to Mongodb server.

• The secret string stored is Mongodb URL (mongo-url: "mongodb://mongo-srv/habits"). Note: in real scenarios, you will use secret to store username and password therefore you should not commit it to your Github account.

5- mongo-pvc

This file has the code for creating the PersistentVolumeClaim resource.

• It requests the K8s node for 2Gi.
• The mode is set to ReadWriteOnce means one node can use it at a time.

6- ingress-srv

This file has the ingress service code.

• It uses the Nginx ingress controller.
• Hosting www.hamid.com (you can edit /etc/hosts file to trick it.)
• It uses regex to identify the request and route to a specific service (i.e client pod or server pod).
• Nginx ingress controller installed by the following link (https://kubernetes.github.io/ingress-nginx/deploy/#quick-start).

Useful commands to check the resources after applying.

To list all the objects in the default namespace

kubectl get all -o wide

To list the services in the default namespace

kubectl get svc -o wide

To list the pods in the default namespace

kubectl get pods -o wide

To list the deployment in the default namespace

kubectl get deployments -o wide

To get all the replicasets

kubectl get replicasets -o wide

To get all the ingress list

kubectl get ingress -o wide

To get all the secrets list

kubectl get secrets -o wide

To get detail of the specific object.

describe argument is used to get details of any object. For example: kubectl describe <object> <name>