# Docker Web Application Deployment (Without Docker Compose)

## Overview
This project deploys a multi-container Docker application consisting of:
- **Flask Web App:** A Python Flask application that connects to a PostgreSQL database.
- **PostgreSQL Database:** Uses the official PostgreSQL image with persistent storage via a named volume.

Both containers communicate over a custom Docker network (`app_network`).

## Required Software
- **Operating System:** Linux (with Docker support)
- **Docker:** Installed and configured
- **Bash:** For running the provided scripts

## Components

### Flask Web Application
- **Image:** Built locally from the Dockerfile in the `app/` folder.
- **Container Name:** `flask_app`
- **Port Mapping:** Host port `5000` mapped to container port `5000`.
- **Environment Variables:** Set via the `docker run` command to point to the database.

### PostgreSQL Database
- **Image:** `postgres:13`
- **Container Name:** `postgres_db`
- **Environment Variables:**
  - `POSTGRES_USER=user`
  - `POSTGRES_PASSWORD=password`
  - `POSTGRES_DB=sampledb`
- **Volume:** Named volume `pgdata` is mounted at `/var/lib/postgresql/data` for persistent storage.

### Virtual Network and Volume
- **Network:** `app_network` – A custom Docker bridge network for inter-container communication.
- **Volume:** `pgdata` – Persists PostgreSQL data between container restarts.

## How to prepare, run, pause and delete the application
# Step 1: Prepare the application
# This will create the necessary volume, network, and build the Flask image.
./prepare-app.sh

# Step 2: Run the application
# This will start the PostgreSQL database and Flask web application containers.
./start-app.sh

# Step 3: Stop the application
# It will stop the containers
./stop-app.sh

# Step 5: Remove the application
# This will stop and remove the containers, network, and volume.
./remove-app.sh


## How to view the application on the web

# Step 1: Ensure that the Flask application is running
# Make sure that the application has been started by running the ./start-app.sh script.
# The Flask application should be accessible at http://localhost:5000.

# Step 2: Open a web browser and enter the following URL:
http://localhost:5000