Starting docker in rails 7.1 with a separate MySQL container

Setting Up MySQL

Pull the MySQL image:
```
docker pull mysql/mysql-server
```
Run the MySQL container:
```
docker run -it -d \
  --name=mysql_container \
  -p 3307:3306 \
  -e MYSQL_ROOT_PASSWORD=password \
  -e MYSQL_ROOT_HOST=% \
  mysql/mysql-server \
  --default-authentication-plugin=mysql_native_password
```
- Explanation:
  - -it: Run in interactive.
  - -d: Run the container in the background.
  - –name=mysql_container: Name the container for easier management.
  - -p 3307:3306: Map the container port 3306 (MySQL) to host port 3307.
  - -e MYSQL_ROOT_PASSWORD=password: Set the root password for the MySQL user.
  - -e MYSQL_ROOT_HOST=%: Allow connections from any host.
  - –default-authentication-plugin=mysql_native_password: Use the traditional password authentication plugin.
Get the container’s IP Address:
```
docker inspect mysql_container | grep IPAddress
```
This will display the container’s IP address, which will be used later.
Set environment variables:
```
export DATABASE_URL='mysql2://root:password@<container_ip>/<db_name>:3306?encoding=utf8mb4'
export RAILS_MASTER_KEY=<rails_master_key>
```
- Replace <container_ip> with the IP address obtained in the previous step.
- Replace <db_name> with the name of the database you want to use.
- Replace <rails_master_key> with the master key from config/master.key.

Build the project image:
```
docker-compose build -t <rails_app> .
```
- Replace <rails_app> with the name you want to give to the image.
- This will build the image using the Dockerfile.
Run the project container:
```
docker run --rm -it -p 3000:3000 --name=<rails_app_container> \
  -e DATABASE_URL=$DATABASE_URL \
  -e RAILS_MASTER_KEY=$RAILS_MASTER_KEY \
  <rails_app>
```
- Replace <rails_app_container> with the name you want to give to the container.
- Replace <rails_app> with the name of the image you built in the previous step.
- Explanation:
  - –rm: Remove the container when it stops.
  - -it: Run in interactive.
  - -p 3000:3000: Map the container port 3000 (Rails) to host port 3000.
  - -e DATABASE_URL=$DATABASE_URL: Set the database URL environment variable.
  - -e RAILS_MASTER_KEY=$RAILS_MASTER_KEY: Set the Rails master key environment variable.

View MySQL container logs:
```
docker logs mysql_container
```
Enter the MySQL container:
```
docker exec -it mysql_container bash
```
- This will open a bash shell inside the container.
- You can then run mysql -u root -p to enter the MySQL command line.
- Use exit to leave the container.