Ruby on Rails デプロイのテスト
Prerequisites
- Complete all the previous sections of this guide, starting with Containerize a Ruby on Rails application.
- Turn on Kubernetes in Docker Desktop.
Overview
In this section, you'll learn how to use Docker Desktop to deploy your application to a fully-featured Kubernetes environment on your development machine. This lets you to test and debug your workloads on Kubernetes locally before deploying.
Create a Kubernetes YAML file
In your docker-ruby-on-rails
directory, create a file named
docker-ruby-on-rails-kubernetes.yaml
. Open the file in an IDE or text editor and add
the following contents. Replace DOCKER_USERNAME/REPO_NAME
with your Docker
username and the name of the repository that you created in
Configure CI/CD for
your Ruby on Rails application.
apiVersion: apps/v1
kind: Deployment
metadata:
name: docker-ruby-on-rails-demo
namespace: default
spec:
replicas: 1
selector:
matchLabels:
service: ruby-on-rails
template:
metadata:
labels:
service: ruby-on-rails
spec:
containers:
- name: ruby-on-rails-container
image: DOCKER_USERNAME/REPO_NAME
imagePullPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
name: docker-ruby-on-rails-demo
namespace: default
spec:
type: NodePort
selector:
service: ruby-on-rails
ports:
- port: 3000
targetPort: 3000
nodePort: 30001
In this Kubernetes YAML file, there are two objects, separated by the ---
:
- A Deployment, describing a scalable group of identical pods. In this case,
you'll get just one replica, or copy of your pod. That pod, which is
described under
template
, has just one container in it. The container is created from the image built by GitHub Actions in Configure CI/CD for your Ruby on Rails application. - A NodePort service, which will route traffic from port 30001 on your host to port 8001 inside the pods it routes to, allowing you to reach your app from the network.
To learn more about Kubernetes objects, see the Kubernetes documentation.
Deploy and check your application
In a terminal, navigate to
docker-ruby-on-rails
and deploy your application to Kubernetes.$ kubectl apply -f docker-ruby-on-rails-kubernetes.yaml
You should see output that looks like the following, indicating your Kubernetes objects were created successfully.
deployment.apps/docker-ruby-on-rails-demo created service/docker-ruby-on-rails-demo created
Make sure everything worked by listing your deployments.
$ kubectl get deployments
Your deployment should be listed as follows:
NAME READY UP-TO-DATE AVAILABLE AGE docker-ruby-on-rails-demo 1/1 1 1 15s
This indicates all one of the pods you asked for in your YAML are up and running. Do the same check for your services.
$ kubectl get services
You should get output like the following.
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 23h docker-ruby-on-rails-demo NodePort 10.99.128.230 <none> 3000:30001/TCP 75s
In addition to the default
kubernetes
service, you can see yourdocker-ruby-on-rails-demo
service, accepting traffic on port 30001/TCP.To create and migrate the database in a Ruby on Rails application running on Kubernetes, you need to follow these steps.
Get the Current Pods: First, you need to identify the pods running in your Kubernetes cluster. Execute the following command to list the current pods in the
default
namespace:# Get the current pods in the cluster in the namespace default $ kubectl get pods
This command will display a list of all pods in the
default
namespace. Look for the pod with the prefixdocker-ruby-on-rails-demo-
. Here is an example output:NAME READY STATUS RESTARTS AGE docker-ruby-on-rails-demo-7cbddb5d6f-qh44l 1/1 Running 2 (22h ago) 9d
Execute the Migration Command: Once you've identified the correct pod, use the
kubectl exec
command to run the database migration inside the pod.$ kubectl exec -it docker-ruby-on-rails-demo-7cbddb5d6f-qh44l -- rails db:migrate RAILS_ENV=development
This command opens an interactive terminal session (
-it
) in the specified pod and runs therails db:migrate
command with the environment set to development (RAILS_ENV=development
).By following these steps, you ensure that your database is properly migrated within the Ruby on Rails application running in your Kubernetes cluster. This process helps maintain the integrity and consistency of your application's data structure during deployment and updates.
Open the browser and go to http://localhost:30001, you should see the ruby on rails application working.
Run the following command to tear down your application.
$ kubectl delete -f docker-ruby-on-rails-kubernetes.yaml
Summary
In this section, you learned how to use Docker Desktop to deploy your application to a fully-featured Kubernetes environment on your development machine.
Related information: