Multiple WordPress sites with one shared DB using Docker

Question

I want to run multiple WordPress websites with one shared database using docker.

Is it possible to specify a database and set an appropriate volume to a certain sql file to initialize WordPress for each container in its docker-compose.yml file?

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For example, I have three docker-compose.yml files for a shared container, siteA and siteB.

When I run docker-compose up in ./shared, two DBs will be created for the two sites (example_a and example_b).

And when I run docker-compose up in ./siteA, I want to change current DB to example_a, and initialize the site with a certain amount of data by sql volumed from ./siteA/mysql/setup.sql.

Same thing goes with siteB.

I know I can specify a database and volume like - WORDPRESS_DB_NAME: example_a and - ./db-data/mysql.dump.sql:/docker-entrypoint-initdb.d/install_wordpress.sql in mysql section in docker-compose.yml but I only have one shared mysql and cannot specify DB and volume for each site.

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I have multiple docker-compose.yml files look something like below.

./shared/docker-compose.yml

version: "2"

services:

  proxy:
    image: jwilder/nginx-proxy
    privileged: true
    container_name: proxy
    ports:
      - 80:80
      - 443:443
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - ./certs:/etc/nginx/certs:ro
    restart: always
    logging:
      options:
        max-size: 5m
        max-file: "10"

  mysql:
    image: mysql:5.7
    container_name: mysql
    command: >
      --character-set-server=utf8mb4
      --collation-server=utf8mb4_general_ci
      --max-allowed-packet=128M
    ports:
      - "3306:3306"
    environment:
      - MYSQL_ROOT_PASSWORD=foobar
    restart: always
    volumes:
      - db-data:/var/lib/mysql
      - ./mysql/sql-setup.sql:/docker-entrypoint-initdb.d/sql-setup.sql # to create multiple databases (e.g. example_a, example_b)
    logging:
      options:
        max-size: 5m
        max-file: "10"

volumes:
  db-data:
    driver: local

networks:
  default:
    external:
      name: shared

./siteA/docker-compose.yml

version: "2"

services:
  example_a_wordpress:
    image: wordpress
    container_name: a.example
    environment:
      WORDPRESS_DB_NAME=example_a
      WORDPRESS_DB_PASSWORD=foobar
      VIRTUAL_HOST: a.example.dev
    external_links:
      - mysql
    restart: always
    volumes:
      - ./dist/theme:/var/www/html/wp-content/themes/main
      - ./dist/assets:/var/www/html/assets
    logging:
      options:
        max-size: 5m
        max-file: "10"

networks:
  default:
    external:
      name: shared

./siteB/docker-compose.yml

version: "2"

services:
  example_b_wordpress:
    image: wordpress
    container_name: b.example
    environment:
    WORDPRESS_DB_NAME=example_b
    WORDPRESS_DB_PASSWORD=foobar
      VIRTUAL_HOST: b.example.dev
    external_links:
      - mysql
    restart: always
    volumes:
      - ./dist/theme:/var/www/html/wp-content/themes/main
      - ./dist/assets:/var/www/html/assets
    logging:
      options:
        max-size: 5m
        max-file: "10"

networks:
  default:
    external:
      name: shared

Answer 1

Yes, you can install multiple WordPress instances into one database. You just need to change the database prefix for each install when installing. Just check your wp-config and change prefix and DBs credentials.

// ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define('DB_NAME', 'database_name_here');

/** MySQL database username */
define('DB_USER', 'username_here');

/** MySQL database password */
define('DB_PASSWORD', 'password_here');

/** MySQL hostname */
define('DB_HOST', 'localhost');

/** Database Charset to use in creating database tables. */
define('DB_CHARSET', 'utf8');

/** The Database Collate type. Don't change this if in doubt. */
define('DB_COLLATE', '');

Answer 2

Did you try setting up table prefix in wp_config.php

$table_prefix  = 'yourcustomname_';

This should resolve the issue with one DB connection on both sites..