Test your Java deployment - Docker

Prerequisites

Complete all the previous sections of this guide, starting with Containerize your app.
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 test and debug your workloads on Kubernetes locally before deploying.

Create a Kubernetes YAML file

In your spring-petclinic directory, create a file named docker-java-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 Java application.

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: docker-java-demo
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      service: server
  template:
    metadata:
      labels:
        service: server
    spec:
      containers:
        - name: server-service
          image: DOCKER_USERNAME/REPO_NAME
          imagePullPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: service-entrypoint
  namespace: default
spec:
  type: NodePort
  selector:
    service: server
  ports:
    - port: 8080
      targetPort: 8080
      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 Java application.
A NodePort service, which will route traffic from port 30001 on your host to port 8080 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 spring-petclinic and deploy your application to Kubernetes.
console
```
$ kubectl apply -f docker-java-kubernetes.yaml
```
You should see output that looks like the following, indicating your Kubernetes objects were created successfully.
shell
```
deployment.apps/docker-java-demo created
service/service-entrypoint created
```

Make sure everything worked by listing your deployments.

console

$ kubectl get deployments

Your deployment should be listed as follows:

shell

NAME                 READY   UP-TO-DATE   AVAILABLE   AGE
docker-java-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.

console

$ kubectl get services

You should get output like the following.

shell

NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes           ClusterIP   10.96.0.1       <none>        443/TCP          23h
service-entrypoint   NodePort    10.99.128.230   <none>        8080:30001/TCP   75s

In addition to the default kubernetes service, you can see your service-entrypoint service, accepting traffic on port 30001/TCP.

In a terminal, curl the service. Note that a database wasn't deployed in this example.

console

$ curl --request GET \
  --url http://localhost:30001/actuator/health \
  --header 'content-type: application/json'

You should get output like the following.

console

{"status":"UP","groups":["liveness","readiness"]}

Run the following command to tear down your application.
console
```
$ kubectl delete -f docker-java-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: