# Notes Application on Kubernetes

## 📌 Description

This project is a simple full-stack **Notes Application** deployed on Kubernetes.
It allows users to create and view notes through a web interface. The application demonstrates a complete **3-tier architecture**:

* Frontend (User Interface)
* Backend (API Server)
* Database (PostgreSQL)

The application is containerized using Docker and deployed using Kubernetes.

---

## 🧱 Application Architecture

The system consists of three main components:

### 1. Frontend

* Built using HTML and JavaScript
* Served via Nginx
* Provides UI for adding and viewing notes
* Communicates with backend using HTTP requests

### 2. Backend

* Built using FastAPI (Python)
* Provides REST API endpoints:

  * `GET /notes`
  * `POST /notes`
* Handles business logic and database interaction

### 3. Database

* PostgreSQL database
* Stores notes persistently
* Managed using Kubernetes StatefulSet

---

## 📦 Containers Used

| Container | Description                                   |
| --------- | --------------------------------------------- |
| frontend  | Nginx container serving static frontend files |
| backend   | FastAPI application handling API requests     |
| postgres  | PostgreSQL database for storing notes         |

---

## ☸️ Kubernetes Objects

| Object                      | Description                                  |
| --------------------------- | -------------------------------------------- |
| Namespace                   | `notes-app` – isolates application resources |
| Deployment                  | Manages frontend and backend pods            |
| StatefulSet                 | Manages PostgreSQL with persistent storage   |
| Service                     | Enables communication between components     |
| PersistentVolume (PV)       | Provides storage for database                |
| PersistentVolumeClaim (PVC) | Requests storage for PostgreSQL              |

---

## 🌐 Networking

* Communication is handled using Kubernetes **Services**
* Backend is accessible via:

  ```
  http://backend-service
  ```
* PostgreSQL is accessible via:

  ```
  postgres
  ```
* Frontend is exposed externally using **NodePort**

---

## 💾 Storage

* PostgreSQL uses persistent storage via:

  * PersistentVolume (PV)
  * PersistentVolumeClaim (PVC)
* Ensures data is retained even if pods restart

---

## ⚙️ Container Configuration

### Backend Configuration

```text
DATABASE_URL=postgresql://user:password@postgres:5432/notesdb
```

### Frontend Configuration

```text
const API_URL = "http://backend-service";
```

---

## 🚀 How to Run the Application

### 1. Prepare the Application

```bash
./scripts/prepare-app.sh
```

Builds Docker images and prepares environment.

---

### 2. Start the Application

```bash
./scripts/start-app.sh
```

Deploys all Kubernetes resources.

---

### 3. Access the Application

#### Option 1: NodePort

```
http://localhost:30007
```

#### Option 2: Port Forward (recommended for Docker Desktop)

```bash
kubectl port-forward service/frontend-service 8080:80 -n notes-app
```

Then open:

```
http://localhost:8080
```

---

### 4. Stop the Application

```bash
./scripts/stop-app.sh
```

Deletes all Kubernetes resources.

---

## 🧪 Functionality

* Users can add notes via UI
* Notes are stored in PostgreSQL
* Data persists across restarts

---

## 📝 Notes

* Docker images are hosted on Docker Hub
* Kubernetes cluster used: Docker Desktop Kubernetes
* Application demonstrates real-world container orchestration

---

## 📚 References

* OpenAI. (2026). ChatGPT (GPT-5.5). https://chat.openai.com
  Used for guidance on Kubernetes deployment, debugging, and structuring the application.

---

## 👨‍💻 Author

Nihal Ahmed