Docker Compose - Can't access Database - mysql

Question

My Docker Wordpress Container some how cannot connect to my database container. I tried to pass the credentials through the environment key.
I'm using external volumes that stores the Data from my previous Wordpress build as well as the data from the Database.
docker-compose.yml
version: '3'
services:
db:
image: mysql:5.7
container_name: db
restart: unless-stopped
env_file: .env
environment:
- MYSQL_DATABASE=wordpress_oxygen
volumes:
- wordpress_db-data:/var/lib/mysql
networks:
- conturas-network
wordpress:
depends_on:
- db
image: wordpress:5.6.0-fpm-alpine
container_name: wordpress
restart: unless-stopped
env_file: .env
environment:
- WORDPRESS_DB_HOST=db:3306
- WORDPRESS_DB_USER=$MYSQL_USER
- WORDPRESS_DB_PASSWORD=$MYSQL_PASSWORD
- WORDPRESS_DB_NAME=wordpress_oxygen
volumes:
- wordpress_data:/var/www/html
networks:
- conturas-network
webserver:
depends_on:
- wordpress
image: nginx:1.19.6-alpine
container_name: webserver
restart: unless-stopped
ports:
- "80:80"
volumes:
- wordpress_data:/var/www/html
- ./nginx-conf:/etc/nginx/conf.d
- certbot-etc:/etc/letsencrypt
networks:
- conturas-network
certbot:
depends_on:
- webserver
image: certbot/certbot
container_name: certbot
volumes:
- certbot-etc:/etc/letsencrypt
- wordpress_data:/var/www/html
command: certonly --webroot --webroot-path=/var/www/html --email username#xyz.io --agree-tos --no-eff-email --force-renewal -d xyz.io -d www.xyz.io
volumes:
certbot-etc:
wordpress_data:
external: true
wordpress_db-data:
external: true
networks:
conturas-network:
driver: bridge
Error Logs from the db-container
...
2020-12-27T15:53:26.593191Z 2 [Note] Access denied for user 'wordpress_oxygen'#'172.30.0.3' (using password: YES)
Thanks for helping!

Answer 1

The very last line of the logs give the important hint on the underlying issue:
[Note] Access denied for user 'wordpress_oxygen'#'172.30.0.3' (using password: YES)
It means that the database credentials used to connect to the database are incorrect - i.e. the username/password combination.
But since this is logged by the database it means WordPress is actually able to connect to the database - i.e. your docker networks are setup correctly.
You should verify now that the values of configured credentials (WORDPRESS_DB_USER, WORDPRESS_DB_PASSWORD etc.) are actually correct - which is the same as MYSQL_USER and MYSQL_PASSWORD used at the time of initializing the database - that is, the environment variables MYSQL_USER, MYSQL_PASSWORD etc. are only used when the database volume is empty and needs to be initialized, see Environment Variables in the image description:
Do note that none of the variables below will have any effect if you start the container with a data directory that already contains a database: any pre-existing database will always be left untouched on container startup.
You may also try to re-initialize the database by deleting the volume and starting a fresh instance of the service.
Also note that environment and env_file two different ways of specifying environment variables for the service, but mixing those two is bad practice since it can lead to unexpected behavior.
If you want to import values from your .env file to use for variable substitution you don't need to "import" it with env_file since it is loaded automatically for docker-compose! I.e. your current configuration does not do what you probably think it does.

Answer 2

What I did to fix the issue
I removed the the environment keys from the whole compose file.
Why did I do this?
I realized with the help of #acran answers, that the volume that I passed into the docker-compose file, was already a ready to use copy of my Initial Wordpress build/installation the same goes for the MySQL Database. (This means all credentials was already stored inside of each volume) Because of that I was not able to pass environment-variables to the composition, to be more precise, you can pass environment-variables to a build but they would simple have no effect on the finished container build.
You can only set environment-variables at the initial build.
Result
version: '3.3'
services:
db:
image: mysql:5.7
container_name: db
restart: unless-stopped
volumes:
- wordpress_db-data:/var/lib/mysql
networks:
- my-network
wordpress:
depends_on:
- db
image: wordpress:5.6.0-fpm-alpine
container_name: wordpress
restart: unless-stopped
volumes:
- wordpress_data:/var/www/html
networks:
- my-network
webserver:
depends_on:
- wordpress
image: nginx:1.19.6-alpine
container_name: webserver
restart: unless-stopped
ports:
- "80:80"
- "443:443"
volumes:
- wordpress_data:/var/www/html
- ./nginx-conf:/etc/nginx/conf.d
- certbot-etc:/etc/letsencrypt
networks:
- my-network
certbot:
depends_on:
- webserver
image: certbot/certbot
container_name: certbot
volumes:
- certbot-etc:/etc/letsencrypt
- wordpress_data:/var/www/html
command: certonly --webroot --webroot-path=/var/www/html --email my.name#xyz.io --agree-tos --no-eff-email --expand --noninteractive -d xyz.io -d www.xyz.io -d dev.xyz.io
volumes:
certbot-etc:
wordpress_data:
external: true
wordpress_db-data:
external: true
networks:
my-network:
driver: bridge