Setting Up a LAMP Stack with Docker Compose

Docker Compose is a tool that allows to declare which Docker containers should run, and which relationships should exist between them. It follows the infrastructure as code approach, just like most automation software and Docker itself.

The docker-compose.yml File

When using Docker Compose, the Docker infrastructure must be described in a YAML file called docker-compose.yml.

Let's see an example:

version: "3"

services:
  web:
    image: "apache:${PHP_VERSION}"
    restart: 'always'
    depends_on:
      - mariadb
    restart: 'always'
    ports:
      - '8080:80'
    links:
      - mariadb
  mariadb:
    image: "mariadb:${MARIADB_VERSION}"
    restart: 'always'
    volumes: 
      - /var/lib/mysql/data:${MARIADB_DATA_DIR
      - /var/lib/mysql/logs:${MARIADB_LOG_DIR
      - /var/docker/mariadb/conf:/etc/mysql
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}

In the first line we declare that we are using the version 3 of the Docker compose language.

Then we have the list of services, namely the web and the mariadb services.

Let's see the properties of the services:

• port maps the 8080 container port to the 80 host system port. This is very useful for a development environment, but not in production, because it allows us to connect our browser to the containerized web server. Normally there is no need to connect to MariaDB from the host system.
• links declares that this container must be able to connect mariadb. The hostname is the container name.
• depends_on declares that mariadb needs to start before web. This is because we cannot do anything with our application until MariaDB is ready to accept connections.
• restart: always declares that the containers must restart if they crashes.
• volumes creates volumes for the container if it is set in a service definition, or a volume that can be used by any container if it is set globally, at the same level as services. Volumes are directories in the host system that can be accessed by any number of containers. This allows to destroy a container without losing data.
• environment sets environment variables inside the container. This is important because setting these variables we set the MariaDB root credentials for the container.

It is a good practice to createe volumes for:

• The data directory, so we don't lose data when a container is created or replaced, perhaps to upgrade MariaDB.
• The directory where we put all the logs, if it is not the datadir.
• The directory containing all configuration files (for development environments), so we can edit those files with the editor installed in the host system. Normally no editor is installed in containers. In production we don't need to to this, because we can copy files from a repository located in the host system to the containers.

Docker Compose Commands

Docker Compose Resources

• Overview of Docker Compose in the Docker documentation
• Compose file in the Docker documentation
• Docker Compose on GitHub

Content initially contributed by Vettabase Ltd.