# KUBERNETES APP DOCUMENTATION  
## AUTHOR : Somangsu Mukherjee

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**1. Conditions for Deployment**

The application requires the following software:

- Docker (version 20 or newer)  
- Kubernetes (Docker Desktop Kubernetes or Minikube)  
- kubectl (configured and working)  
- Bash shell (WSL recommended on Windows)  
- Internet connection (to download container images)  

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**2. Application Description**

This is a Kubernetes-based multi-container web application.

The application allows users to:

- Enter their name in a web interface  
- Submit the name to a backend server  
- Store the name in a PostgreSQL database  
- Retrieve and display all stored names  

The application demonstrates communication and orchestration of multiple services using Kubernetes.

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**3. Virtual Networks and Volumes**

**Virtual Network**

Kubernetes automatically manages networking between services and pods using internal DNS.

Services communicate using service names:

- Backend communicates with database (`db`)  
- External users access backend through NodePort service  

**Named Volume**

Persistent storage is implemented using:

- PersistentVolume (PV)  
- PersistentVolumeClaim (PVC)  

These are mounted to `/var/lib/postgresql/data` inside the PostgreSQL container  

This ensures that data is preserved even if pods are restarted or recreated  

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**4. Container Configuration**

**Backend**

- Image: `docker-app-backend:latest`  
- Port: `3000`  
- Built using Node.js and Express framework  
- Communicates with PostgreSQL database to store and retrieve names  
- Deployed using Kubernetes Deployment  

**Database (PostgreSQL)**

- Image: `postgres:15`  
- Port: `5432`  
- Environment variables:  
  - `POSTGRES_USER=user`  
  - `POSTGRES_PASSWORD=password`  
  - `POSTGRES_DB=mydb`  

The database uses PersistentVolume and PersistentVolumeClaim for persistence which ensures that data is not lost even after pod restarts  

Uses StatefulSet for stable identity and storage  

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**5. The table below describes all the components utilised in this assignment**

| Component    | Description                                      |
|--------------|--------------------------------------------------|
| Namespace    | Isolates all application resources               |
| Deployment   | Runs Node.js backend application                 |
| StatefulSet  | Runs PostgreSQL database with persistent storage |
| Service      | Exposes backend externally using NodePort        |
| DB Service   | Enables internal communication with database     |

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**6. Application Control**

**Prepare Application:**
To prepare the application, the backend image must be built using:

docker build -t docker-app-backend ./backend

**Start Application:**
Run the following command in WSL:

./start-app.sh

This creates all Kubernetes resources and starts the application

Stop Application
To stop the application:

./stop-app.sh

**Remove Application**
Deleting the namespace removes all resources completely:

kubectl delete namespace myapp

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**7. Accessing the Application**

Backend API can be accessed at:
http://localhost:30007
Frontend can be accessed by opening:
frontend/index.html

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**8. Used Resources**

Kubernetes official documentation
Docker documentation
Node.js documentation
PostgreSQL documentation

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**9. Use of Artificial Intelligence**

Artificial intelligence tools were used as a support tool during development for understanding Kubernetes concepts and debugging deployment issues. Some configuration problems were resolved with AI assistance. All implementation, testing, and integration were performed independently.