How to put containers network to the kubernetes YAML file - mysql

Question

For exmaple, I created network at docker
docker network create hello-rails
Then, I have mySQL, which is connected to this network
docker run -p 3306 -d --network=hello-rails --network-alias=db -e MYSQL_ROOT_PASSWORD=password --name hello-rails-db mysql
And also, I have rails server, which also rely on this network
docker run -it -p 3000:3000 --network=hello-rails -e MYSQL_USER=root -e MYSQL_PASSWORD=password -e MYSQL_HOST=db --name hello-rails benjamincaldwell/hello-docker-rails:latest
I want to write deployment on kubernetes for these two containers with YAML file. But I don't know, how to put network inside containers in the file. Do you have any recommendations?

Answer 1

In Kubernetes you would solve this by creating two services.
The MySQL service will look something like this:
kind: Service
apiVersion: v1
metadata:
name: mysql
spec:
selector:
app: mysql
ports:
- port: 3306
In your rails server, you can access the MySQL service by either using the mysql DNS name or using the MYSQL_SERVICE_HOST and MYSQL_SERVICE_PORT environment variables. There is no need to link the containers or specifying a network, as would be done in Docker.
Your Rails service will look like this:
kind: Service
apiVersion: v1
metadata:
name: rails
spec:
type: LoadBalancer
selector:
app: rails
ports:
- port: 3000
Notice the type: LoadBalancer, which specifies that this service will be published to the outside world. Depending on where you run Kubernetes, a public IP address will be automatically assigned to this service.
For more information, have a look at the Services documentation.