demo-hello.adoc

Demo - Hello App deployed on Kubernetes

Simple Hello Spring Boot app deployment on Minikube

Start Minikube

• Install Minikube from https://kubernetes.io/docs/tasks/tools/install-minikube/

• Install kubectl from https://kubernetes.io/docs/tasks/tools/install-kubectl/

Then, start Minikube:

minikube start

Create and run a simple Spring Boot app

1. Create a simple Boot app (You can also use Spring Initializr web interface)

   curl https://start.spring.io/starter.zip -d bootVersion=2.0.0.M5 \
        -d dependencies=web,actuator \
        -d groupId=com.springdeveloper.k8s -d artifactId=hello \
        -d name=hello -d baseDir=hello -o hello.zip
   unzip hello.zip
   cd hello

Note	We are using the most Spring Boot 2.0 M5, as of Nov 6 there is a new M6 milestone available.

1. Add a @RestController and a mapping for /hello (the bold parts are the additions):

   src/main/java/com/springdeveloper/k8s/demo/HelloApplication.java

   package com.springdeveloper.k8s.hello;
   
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   @SpringBootApplication
   public class HelloApplication {
   	public static void main(String[] args) {
   		SpringApplication.run(HelloApplication.class, args);
   	}
   
   	@RestController
   	class HelloController {
   		@GetMapping("/hello")
   		String hello() {
   			return "Hello Kubernauts!";
   		}
   	}
   }

2. Add a property enabling the /application/env endpoint. This allows us to inspect environment variables added by Kubernetes.

   src/main/resources/application.properties

   endpoints.env.enabled=true

3. Create a Dockerfile so we can package this app as a Docker image

   Dockerfile

   FROM java:8-alpine
   VOLUME /tmp
   ADD ./target/hello-0.0.1-SNAPSHOT.jar /hello.jar
   RUN sh -c 'touch /hello.jar'
   ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/hello.jar"]

4. Build the app and the Docker image

   Note	We are sharing the Docker environment used by Minikube

   eval $(minikube docker-env)
   ./mvnw clean package
   docker build -t $USER/hello:0.0.1 .

5. Run a Kubernetes deployment on the running Minikube cluster

   kubectl run hello --image $USER/hello:0.0.1 --port 8080
   kubectl expose deployment hello --type=NodePort

6. Test the app

   curl $(minikube service hello --url)/hello

7. Inspect environment variables and Kubernetes deployment/service yaml

   curl $(minikube service hello --url)/application/env | python -m json.tool
   kubectl get deploy/hello -o yaml
   kubectl get svc/hello -o yaml

8. Create Deployment and Service YAML files for future repeatable deployments

   ProTip from Joe Beda at Heptio: https://blog.heptio.com/using-kubectl-to-jumpstart-a-yaml-file-heptioprotip-6f5b8a63a3ea

   kubectl run hello --image $USER/hello:0.0.1 --port 8080 -o yaml --dry-run \
       > hello-deployment.yaml
   kubectl expose deployment hello --type=NodePort -o yaml --dry-run > hello-svc.yaml

9. Delete the resources created for hello

   kubectl delete all -l run=hello