Port mapping in Compose in Docker - Mini Project: Build & Apply

Port mapping in Compose

📖 Scenario: You are setting up a simple web application using Docker Compose. The application runs inside a container and listens on port 80. To access it from your computer's browser, you need to map the container's port 80 to a port on your computer.

🎯 Goal: Learn how to write a Docker Compose file that maps a container port to a host port so you can access the application from your browser.

📋 What You'll Learn

Create a Docker Compose file named docker-compose.yml

Define a service called webapp using the nginx image

Map container port 80 to host port 8080 using port mapping

💡 Why This Matters

🌍 Real World

Port mapping is essential to access applications running inside containers from your computer or other devices on the network.

💼 Career

Understanding Docker Compose port mapping helps in deploying and managing containerized applications in development and production environments.

1

Create the basic Docker Compose file

Create a file named docker-compose.yml and write the starting lines to define the version as '3.8' and an empty services section.

Docker

# Write the version and services section in docker-compose.yml
# Your code here

Need a hint?

Start with version: '3.8' on the first line, then add services: below it.

2

Add the webapp service with nginx image

Under the services section, add a service named webapp that uses the nginx image.

Docker

version: '3.8'
services:
  # Add webapp service with nginx image here
  # Your code here

Need a hint?

Indent the webapp service under services: and specify image: nginx under it.

3

Add port mapping to expose container port 80 on host port 8080

Inside the webapp service, add a ports section that maps host port 8080 to container port 80.

Docker

version: '3.8'
services:
  webapp:
    image: nginx
    # Add ports mapping here
    # Your code here

Need a hint?

Use ports: followed by - "8080:80" indented properly under webapp.

4

Run Docker Compose and check port mapping

Run docker compose up -d in your terminal to start the container. Then run docker compose ps and write the output showing the port mapping line for the webapp service.

Docker

# Run 'docker compose up -d' in terminal
# Then run 'docker compose ps' and write the output below
# Your code here

Need a hint?

After starting the container, docker compose ps shows the port mapping like 0.0.0.0:8080->80/tcp.