How to create Mysql test database in dockerized Rails application? - mysql

Question

I managed to dockerize my existing Rails application running on a Mysql database. But I wonder if it is possible to setup docker-compose to create the test database in the same container?
Here is my docker-compose.yml and it wirks fine with the mysql for developing
version: '2'
volumes:
db-data:
services:
db:
image: mysql:5.5
restart: always
ports:
- "3307:3306"
environment:
MYSQL_ROOT_PASSWORD: verysecret
MYSQL_USER: appdb
MYSQL_PASSWORD: secret
MYSQL_DATABASE: appdb
volumes:
- db-data:/var/lib/mysql
web:
build: .
command: bundle exec rails s -p 3000
volumes:
- .:/app
ports:
- "3000:3000"
links:
- db
depends_on:
- db
Can I add a darabase more in environment part somehow?

Answer 1

You can create only one DB per Mysql container with docker compose. In your case, I think you should create a second DB container for the second database (isolated from the "real" DB, which is a good practice).
If you really want to have the 2 databases in the same container, you will have to create a Dockerfile based on the Mysql image, and add your command lines (RUN) to create the second DB.
HTH

Answer 2

Yes, you can, but it won't necessarily be as a single container, but a manager for coupling containers. If this is okay, I've added some steps that will help you configure your project. If not, I've added how to run a single image from a docker-compose file
You will want to start off by creating a docker-compose.yml file in the source directory for your project.
Then you'll want to add something like this inside your yml file.(this was taken from Docker's quick-start documentation. Modified to show mysql instead of postgres)
version: '3'
services:
db:
image: mysql
web:
build: .
command: bundle exec rails s -p 3306 -b '0.0.0.0'
volumes:
- .:/myapp
ports:
- "3000:3000"
depends_on:
- db
Detail on how they create one can be found here:
https://docs.docker.com/compose/rails/#define-the-project.
Things to note:
web is the details about the rails container. So you will want to add an image property if you have already created your rails image.
Also, build: . is expecting your Dockerfile to be in the same location as your project. So if you create this docker-compose.yml somewhere else, you'll have to provide the path.
depends_on allows your app to build the DB before running rails
Once you finished creating the docker-compose.yml file run:
docker-compose build
followed by:
docker-compose up
If separating the containers, isn't what you are looking for: then you might want to look into creating a single image running both applications. Then use something like this to run from docker-compose.
version: '3'
services:
app:
image: {your-app-image}
build: .
volumes:
- .:/myapp
ports:
- "3000:3000"
- "3306:3306"
Note: somethings might vary on how you create your image from the Dockerfile.