Debug application
At this point, we deployed our application within a local cluster. But now we have a problem. How do I debug my application that is inside the docker that is inside the kubernetes that is inside a virtual machine?
Prepare to debug
In this case, we will use a remote Java debug.
First step:
Prepare your Dockerfile:
FROM openjdk:11.0.3-jdk-slim
RUN mkdir /usr/myapp
COPY target/java-kubernetes.jar /usr/myapp/app.jar
WORKDIR /usr/myapp
EXPOSE 8080
ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -jar app.jar" ]
This ENTRYPOINT allows you to pass options to the java through $JAVA_OPTS environment variable.
Second step:
Changing app-configmap.yaml file to fill $JAVA_OPTS.
JAVA_OPTS: "-agentlib:jdwp=transport=dt_socket,address=*:5005,server=y,suspend=n -Xms256m -Xmx512m -XX:MaxMetaspaceSize=128m"
Third step:
Building and deploy app:
mvn clean install
eval $(minikube -p dev.to docker-env) && docker build --force-rm -t java-k8s .
kubectl apply -f kubernetes/app/
Fourth step:
Exposing debug port to localhost:
Get pods:
kubectl get pods -n dev-to
NAME READY STATUS RESTARTS AGE
myapp-7796bc89bf-h2f82 1/1 Running 0 3h3m
Expose pod 5005 port:
kubectl port-forward -n dev-to myapp-7796bc89bf-h2f82 5005:5005
Forwarding from 127.0.0.1:5005 -> 5005
Forwarding from [::1]:5005 -> 5005
Change your pod name as necessary.
Create a remote debug on your IDE:
On IntelliJ, go to Run/Debug Configurations.
- Add new remote configuration like this:
After that, run the configuration. You should see the message below:
Connected to the target VM, address: 'localhost:5005', transport: 'socket'
Check if works:
Now, you can set a breakpoint in the HelloController.
minikube -p dev.to service -n dev-to myapp --url
http://192.168.99.100:32301
curl http://192.168.99.100:32301/hello
Conclusion
In this part, we learned about how to debug application inside a local kubernetes cluster.
In the next part, we will see some good practices and how to access application with friendly URL using Ingress.
See you soon!
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