Docker Compose for dev environment - Commands & Configuration

Introduction

When you develop software, you often need several services like a web server and a database to work together. Docker Compose helps you start and manage these services easily with one command, so you can focus on coding instead of setup.

When you want to run a web app and a database together on your computer without installing them separately.

When you need to share your development setup with teammates so everyone uses the same environment.

When you want to quickly start and stop multiple services with one command during development.

When you want to avoid conflicts between different projects by isolating their services.

When you want to test how your app works with other services like Redis or message queues locally.

Config File - docker-compose.yml

docker-compose.yml

version: '3.8'
services:
  web:
    image: nginx:1.23
    ports:
      - "8080:80"
    volumes:
      - ./html:/usr/share/nginx/html:ro
  db:
    image: postgres:15
    environment:
      POSTGRES_USER: devuser
      POSTGRES_PASSWORD: devpass
      POSTGRES_DB: devdb
    ports:
      - "5432:5432"
    volumes:
      - db-data:/var/lib/postgresql/data
volumes:
  db-data: {}

This file defines two services: web and db.

The web service uses the nginx image and maps port 8080 on your computer to port 80 inside the container. It also mounts a local html folder as read-only to serve your web files.

The db service uses the postgres image with environment variables to set up the database user, password, and database name. It maps port 5432 and uses a volume to keep data persistent.

The volumes section creates a named volume db-data to store database files outside the container.

Commands

This command starts all services defined in the docker-compose.yml file in the background. It creates containers, networks, and volumes as needed.

Terminal

docker-compose up -d

Expected Output

Creating network "default" with the default driver

Creating volume "db-data" with default driver

Creating devenvironment_web_1 ... done

Creating devenvironment_db_1  ... done

→

-d - Run containers in detached mode (in the background)

This command lists all running containers started by Docker Compose, showing their status and ports.

Terminal

docker-compose ps

Expected Output

    Name                   Command               State           Ports         

--------------------------------------------------------------------------------

devenvironment_db_1   docker-entrypoint.sh postgres   Up      0.0.0.0:5432->5432/tcp

 devenvironment_web_1  nginx -g 'daemon off;'          Up      0.0.0.0:8080->80/tcp

This command shows the logs from the web service container, useful to check if the web server started correctly.

Terminal

docker-compose logs web

Expected Output

[devenvironment_web_1] 2024/06/01 12:00:00 [notice] 1#1: using the "epoll" event method

[devenvironment_web_1] 2024/06/01 12:00:00 [notice] 1#1: nginx/1.23.0 started

This command stops and removes all containers, networks, and default volumes created by Docker Compose, cleaning up your environment.

Terminal

docker-compose down

Expected Output

Stopping devenvironment_web_1 ... done

Stopping devenvironment_db_1  ... done

Removing devenvironment_web_1 ... done

Removing devenvironment_db_1  ... done

Removing network default

Key Concept

If you remember nothing else from this pattern, remember: Docker Compose lets you start and stop multiple related services with one simple file and commands.

Common Mistakes

Not mapping ports in the docker-compose.yml file

Without port mapping, you cannot access the services from your computer, so your app won't work as expected.

Always map container ports to your local machine ports using the ports section.

Running 'docker-compose up' without the -d flag and closing the terminal

The containers stop when the terminal closes because they run in the foreground.

Use 'docker-compose up -d' to run containers in the background.

Not using volumes for persistent data like databases

Data will be lost when containers are removed if volumes are not used.

Define volumes in docker-compose.yml to keep data safe across container restarts.

Summary

Use docker-compose.yml to define multiple services and how they connect.

Start all services together with 'docker-compose up -d' and check their status with 'docker-compose ps'.

Stop and clean up services with 'docker-compose down' to keep your environment tidy.