# Assignment 1 – Docker Notes App

##  Overview

This project is a simple **Notes Application** built using Docker.  
It demonstrates how to run a multi-container application composed of:

- Frontend (Nginx)
- Backend (Flask REST API)
- Database (PostgreSQL)

The application allows users to:
- Add notes
- View saved notes
- Delete notes

All data is stored persistently using a Docker volume.

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##  Architecture

The application consists of three services:

### 1. Frontend
- Technology: Nginx
- Serves static HTML page
- Proxies API requests to backend
- Accessible via browser

### 2. Backend
- Technology: Python (Flask)
- Provides REST API:
  - `GET /api/notes`
  - `POST /api/notes`
  - `DELETE /api/notes/{id}`
- Connects to PostgreSQL database

### 3. Database
- Technology: PostgreSQL 16
- Stores notes data
- Uses persistent Docker volume

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##  Networking

All containers are connected via a Docker virtual network:

- **Network name:** `zkt_net`

This allows communication between:
- frontend → backend
- backend → database

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## Persistent Storage

- **Volume name:** `zkt_db_data`
- Purpose: store PostgreSQL data
- Ensures data is not lost after stopping containers

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## Containers Used

| Container Name  | Description            |
|----------------|------------------------|
| zkt_frontend   | Nginx web server       |
| zkt_backend    | Flask API              |
| zkt_db         | PostgreSQL database    |

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##  Requirements

- Docker
- Docker Compose (plugin)
- Linux / WSL / Docker Desktop
- Web browser

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##  How to Run the Application

### 1. Prepare the application

```bash
./prepare-app.sh

### 2. Start the application 

./start-app.sh

### Then open your browser:

 http://localhost:8080 
 
 
### 3. Stop the application
./stop-app.sh

### 4. Remove the application
./remove-app.sh

## Testing the Application

-Open the web interface
-Add a note
-Verify it appears in the list
-Stop and restart the app:
./stop-app.sh
./start-app.sh
-Refresh the page

## If the note is still there → persistence works correctly

## Key Concepts Demonstrated

-Multi-container Docker application
-Docker Compose usage
-Container networking
-Persistent storage with volumes
-REST API communication
-Reverse proxy with Nginx

## Use of Artificial Intelligence

Artificial intelligence was used to:

-Design application architecture
-Generate initial code (frontend, backend, Docker config)
-Explain Docker concepts
-Assist with debugging and troubleshooting
-Prepare documentation

## Tool used:

-ChatGPT
-Gemini

## Pablo Pérez Arcas