[FIXED] Moving Wordpress site to Docker: Error establishing DB connection

Issue

Ive been making new sites with Wordpress & Docker recently and have a reasonable grasp of how it all works and Im now looking to move some established sites into Docker.

Ive been following this guide:

https://stephenafamo.com/blog/moving-wordpress-docker-container/

I have everything setup as it should be but when I go to my domain.com:1234 I get the error message 'Error establishing a database connection'. I have changed 'DB HOST' to 'mysql' in wp-config.php as advised and all the DB details from the site Im bringing in are correct.

I have attached to the mysql container and checked that the db is there and with the right user and also made sure the pw is correct via mysql CLI too.

SELinux is set to permissive and I havent changed any dir/file ownership nor permissions and for the latter dirs are all 755 and files 644 as they should be.

Edit: I should mention that database/data and everything under that seem to be owned by user/group 'polkitd input' instead of root.

Docker logs aren't really telling me much either apart from the 500 error messages for the WP container when I browse the site on port 1234 (as expected though).

This is the docker-compose file:

version: '2'

services:
  example_db:
    image: mysql:latest
    container_name: example_db
    volumes:
      - ./database/data:/var/lib/mysql
      - ./database/initdb.d:/docker-entrypoint-initdb.d
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: password123 # any random string will do
      MYSQL_DATABASE: mydomin_db # the name of your mysql database
      MYSQL_USER: my domain_me # the name of the database user
      MYSQL_PASSWORD: password123 # the password of the mysql user

  example:
    depends_on:
      - example_db
    image: wordpress:php7.1 # we're using the image with php7.1
    container_name: example
    ports:
      - "1234:80"
    restart: always
    links:
      - example_db:mysql
    volumes:
      - ./src:/var/www/html

Suggestions most welcome as Im out of ideas!

Solution

Please take a look at the following compose script. I tried and tested. It works fine.

version: '2'

services:
  db:
    image: mysql:latest
    container_name: db_server
    volumes:
      - ./database/data:/var/lib/mysql
      - ./database/initdb.d:/docker-entrypoint-initdb.d
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: password123 # any random string will do
      MYSQL_DATABASE: udb_test # the name of your mysql database
      MYSQL_USER: me_prname # the name of the database user
      MYSQL_PASSWORD: password123 # the password of the mysql user

  example:
    depends_on:
      - db
    image: wordpress:php7.1 # we're using the image with php7.1
    container_name: wp-web
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: me_prname
      WORDPRESS_DB_PASSWORD: password123
      WORDPRESS_DB_NAME: udb_test
    ports:
      - "1234:80"
    restart: always
    volumes:
      - ./src:/var/www/html

Let me know if you encounter further issues.

Answered By - cooshal