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z1/Dockerfile

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+# Use an official lightweight Python image
+FROM python:3.8-slim
+
+# Set the working directory in the container
+WORKDIR /app
+
+# Copy the application code into the container
+COPY app.py /app/
+
+# Install required Python packages: Flask and MySQL connector
+RUN pip install flask mysql-connector-python
+
+# Expose port 5000 for the Flask app
+EXPOSE 5000
+
+# Set the environment variable for Flask
+ENV FLASK_APP=app.py
+
+# Run the Flask application
+CMD ["flask", "run", "--host=0.0.0.0", "--port=5000"]

z1/README.md

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+# Docker Web Application
+
+## Overview
+This is a Dockerized web application consisting of two services:
+- **Web Service:** A simple Python Flask application serving HTTP endpoints.
+- **Database Service:** A MySQL 8.0 database that stores its data in a persistent volume.
+
+The web service demonstrates basic functionality and includes an endpoint (`/dbtest`) to test connectivity with the database service.
+
+## Deployment Requirements
+- **Docker:** Ensure Docker is installed and running.
+- **Docker Compose:** Version 3.8 or later is required to run the multi-container application.
+
+## Application Architecture
+- **Virtual Network:**  
+  A custom Docker network `app-network` is used to allow seamless communication between containers.
+  
+- **Named Volume:**  
+  A persistent volume `db_data` is defined to store MySQL database data, ensuring data persistence between container restarts.
+
+## Container Configurations
+- **Web Service Container:**
+  - **Image:** Custom built from the provided `Dockerfile`.
+  - **Port:** Exposes port `5000`.
+  - **Environment Variables:** Set for database connectivity (e.g., `MYSQL_HOST`, `MYSQL_USER`, `MYSQL_PASSWORD`, `MYSQL_DATABASE`).
+  - **Restart Policy:** Configured to always restart on failure.
+  
+- **Database Service Container:**
+  - **Image:** Official `mysql:8.0` image.
+  - **Ports:** Exposes port `3306`.
+  - **Environment Variables:** Defines `MYSQL_ROOT_PASSWORD` and `MYSQL_DATABASE` for initial configuration.
+  - **Volume:** Uses named volume `db_data` for data persistence.
+  - **Restart Policy:** Configured to always restart on failure.
+
+## Used Containers
+- **web:** The Flask-based web server.
+- **db:** The MySQL database server.
+
+## How to Use the Application
+
+1. **Prepare the Application:**  
+   Run the following command to build images and create required networks/volumes:
+   ```bash
+   ./prepare-app.sh
+
+2. **Start the Application:** 
+    Launch the containers with:
+        ./start-app.sh
+    You should see a message:
+        Running app ...
+        The app is available at http://localhost:5000
+
+3. **Interact with the Application:**
+
+    • Open your web browser and go to http://localhost:5000 to view the home page.
+    • Visit http://localhost:5000/status for the application status.
+    • Visit http://localhost:5000/dbtest to test the database connectivity.
+
+4. **Stop the Application:**
+    To stop all running services without removing their state:
+        ./stop-app.sh
+
+5. **Remove the Application:**
+    When you want to completely remove all containers, networks, and volumes:
+        ./remove-app.sh

z1/app.py

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+from flask import Flask, jsonify
+import os
+import mysql.connector
+from mysql.connector import Error
+
+app = Flask(__name__)
+
+@app.route("/")
+def home():
+    # Basic endpoint to verify that the app is running
+    return "Hello, world! The app is working."
+
+@app.route("/status")
+def status():
+    # Returns the status of the application
+    return jsonify(status="OK")
+
+@app.route("/dbtest")
+def dbtest():
+    # Attempts to connect to the MySQL database using environment variables
+    try:
+        connection = mysql.connector.connect(
+            host="db",
+            user=os.environ.get("MYSQL_USER", "root"),
+            password=os.environ.get("MYSQL_PASSWORD", "example"),
+            database=os.environ.get("MYSQL_DATABASE", "exampledb"),
+            port=3306
+        )
+        if connection.is_connected():
+            connection.close()
+            return "Successfully connected to the database."
+    except Error as e:
+        return f"Error connecting to database: {e}"
+
+if __name__ == "__main__":
+    # Run the app on port 5000 and make it accessible from any network interface
+    app.run(debug=True, host="0.0.0.0", port=5000)

z1/docker-compose.yaml

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+version: '3.8'
+
+services:
+  web:
+    build: .
+    ports:
+      - "5000:5000"
+    depends_on:
+      - db
+    restart: always
+    environment:
+      # Environment variables for connecting to the database
+      MYSQL_HOST: db
+      MYSQL_USER: "root"
+      MYSQL_PASSWORD: "example"
+      MYSQL_DATABASE: "exampledb"
+    networks:
+      - app-network
+
+  db:
+    image: mysql:8.0
+    restart: always
+    environment:
+      MYSQL_ROOT_PASSWORD: "example"
+      MYSQL_DATABASE: "exampledb"
+    volumes:
+      - db_data:/var/lib/mysql
+    ports:
+      - "3306:3306"
+    networks:
+      - app-network
+
+networks:
+  app-network:
+    driver: bridge
+
+volumes:
+  db_data:

z1/prepare-app.sh

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+#!/bin/bash
+# prepare-app.sh: Prepares the Docker application environment.
+# This script builds Docker images, and creates necessary networks and named volumes.
+
+# Build the Docker images defined in docker-compose.yaml
+docker-compose build
+
+# Create the application network if it doesn't exist (optional, as docker-compose creates one automatically)
+docker network create app-network 2>/dev/null || echo "Network 'app-network' already exists."
+
+# Create the named volume for MySQL database persistence (optional, docker-compose will create it if missing)
+docker volume create db_data 2>/dev/null || echo "Volume 'db_data' already exists."
+
+echo "Preparing app completed."

z1/remove-app.sh

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+#!/bin/bash
+# remove-app.sh: Removes all Docker application services and cleans up networks and volumes.
+# This script removes all resources created by prepare-app.sh.
+
+docker-compose down --volumes --remove-orphans
+
+echo "Removed app."

z1/start-app.sh

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+#!/bin/bash
+# start-app.sh: Starts the Docker application services.
+# This script launches all containers in detached mode and configures them to restart on failure.
+
+docker-compose up -d
+
+echo "Running app ..."
+echo "The app is available at http://localhost:5000"

z1/stop-app.sh

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+#!/bin/bash
+# stop-app.sh: Stops the Docker application services without removing containers or volumes.
+# This ensures the current state is maintained even if configuration changes later.
+
+docker-compose stop
+
+echo "Stopping app..."