Java and Kubernetes

Show how you can move your spring boot application to docker and kubernetes. This project is a demo for the series of posts on dev.to https://dev.to/sandrogiacom/kubernetes-for-java-developers-setup-41nk

Part one - base app:

Requirements:

Docker and Make (Optional)

Java 15

Help to install tools:

https://github.com/sandrogiacom/k8s

Build and run application:

Spring boot and mysql database running on docker

Clone from repository

git clone https://github.com/sandrogiacom/java-kubernetes.git

Build application

cd java-kubernetes
mvn clean install

Start the database

make run-db

Run application

java --enable-preview -jar target/java-kubernetes.jar

Check

http://localhost:8080/app/users

http://localhost:8080/app/hello

Part two - app on Docker:

Create a Dockerfile:

FROM openjdk:15-alpine
RUN mkdir /usr/myapp
COPY target/java-kubernetes.jar /usr/myapp/app.jar
WORKDIR /usr/myapp
EXPOSE 8080
ENTRYPOINT [ "sh", "-c", "java --enable-preview $JAVA_OPTS -jar app.jar" ]

Build application and docker image

make build

Create and run the database

make run-db

Create and run the application

make run-app

Check

http://localhost:8080/app/users

http://localhost:8080/app/hello

Stop all:

docker stop mysql57 myapp

Part three - app on Kubernetes:

We have an application and image running in docker Now, we deploy application in a kubernetes cluster running in our machine

Prepare

Start minikube

make k-setup start minikube, enable ingress and create namespace dev-to

Check IP

minikube -p dev.to ip

Minikube dashboard

minikube -p dev.to dashboard

Deploy database

create mysql deployment and service

make k-deploy-db

kubectl get pods -n dev-to

OR

watch k get pods -n dev-to

kubectl logs -n dev-to -f <pod_name>

kubectl port-forward -n dev-to <pod_name> 3306:3306

Build application and deploy

build app

make k-build-app

create docker image inside minikube machine:

make k-build-image

OR

make k-cache-image

create app deployment and service:

make k-deploy-app

Check

kubectl get services -n dev-to

To access app:

minikube -p dev.to service -n dev-to myapp --url

Ex:

http://172.17.0.3:32594/app/users http://172.17.0.3:32594/app/hello

Check pods

kubectl get pods -n dev-to

kubectl -n dev-to logs myapp-6ccb69fcbc-rqkpx

Map to dev.local

get minikube IP minikube -p dev.to ip

Edit hosts

sudo vim /etc/hosts

Replicas kubectl get rs -n dev-to

Get and Delete pod kubectl get pods -n dev-to

kubectl delete pod -n dev-to myapp-f6774f497-82w4r

Scale kubectl -n dev-to scale deployment/myapp --replicas=2

Test replicas while true do curl "http://dev.local/app/hello" echo sleep 2 done Test replicas with wait

while true do curl "http://dev.local/app/wait" echo done

Check app url

minikube -p dev.to service -n dev-to myapp --url

Change your IP and PORT as you need it

curl -X GET http://dev.local/app/users

Add new User curl --location --request POST 'http://dev.local/app/users' \ --header 'Content-Type: application/json' \ --data-raw '{ "name": "new user", "birthDate": "2010-10-01" }'

Part four - debug app:

add JAVA_OPTS: "-agentlib:jdwp=transport=dt_socket,address=*:5005,server=y,suspend=n"

change CMD to ENTRYPOINT on Dockerfile

kubectl get pods -n=dev-to

kubectl port-forward -n=dev-to <pod_name> 5005:5005

KubeNs and Stern

kubens dev-to

stern myapp

Start all

make k:all

References

https://kubernetes.io/docs/home/

https://minikube.sigs.k8s.io/docs/

Useful commands

##List profiles
minikube profile list

kubectl top node

kubectl top pod <nome_do_pod>