Changing port of mariadb in docker-compose

Question

I run a number of WordPress sites using docker-compose (and nginx-proxy). So I can use the same docker-compose file for each site I use .env. I want each of the MariaDB containers to use different ports (as they are sharing the same external docker network).

What I have is the below compose file but when I bring it up I get.

MySQL Connection Error: (2002) Connection refused 

Previously I was using the same compose file without the ports: section and with the port hardcoded in the WordPress section and it worked.

Where did I go wrong?

docker-compose.yml

version: '3' services: db: image: mariadb container_name: ${DB_CONTAINER} hostname: ${DB_CONTAINER} ports: - ${DB_PORT}:3306 volumes: - ./db:/var/lib/mysql restart: always environment: MYSQL_ROOT_PASSWORD: ${DB_ROOT_PASSWORD} MYSQL_DATABASE: wordpress MYSQL_USER: wordpress MYSQL_PASSWORD: ${DB_WP_PASSWORD} wordpress: depends_on: - db image: wordpress:latest restart: always container_name: ${WP_CONTAINER} hostname: ${WP_CONTAINER} volumes: - ./html:/var/www/html expose: - 80 restart: always environment: VIRTUAL_HOST: ${DOMAINS} LETSENCRYPT_HOST: ${DOMAINS} LETSENCRYPT_EMAIL: ${EMAIL} WORDPRESS_DB_HOST: db:${DB_PORT} WORDPRESS_DB_USER: wordpress WORDPRESS_DB_PASSWORD: ${DB_WP_PASSWORD} networks: default: external: name: nginx-proxy 

.env

DB_CONTAINER=test_click_db WP_CONTAINER=test_click_wp DB_PORT=13306 [email protected] DOMAINS=test.click.tvpp.tv DB_ROOT_PASSWORD=aabbcc DB_WP_PASSWORD=xxyyzz 

Answer 1

Actually I worked it out the db service needed the following added to environment:

MYSQL_TCP_PORT: ${DB_PORT} MYSQL_UNIX_PORT: ${DB_PORT} 

Answer 2

This line

WORDPRESS_DB_HOST: db:${DB_PORT} 

should be changed to

WORDPRESS_DB_HOST: db:3306 

(I guess this actually is what you did previously) The wordpress container will then connect directly to the mariadb container at port 3306 of the container. The db part is resolved by docker network's internal DNS server to the IP address of your mariadb container.

You don't need this part

ports: - ${DB_PORT}:3306 

It means that docker will map the ${DB_PORT} on your host machine to port 3306 in the service (container), thus you can also reach the DB by connecting to the host machine at port ${DB_PORT}. It's generally only for when you intend to connect to the container from outside the host machine.