Remote Debug K8s Java Application

This page provide a way to using IDEA detach debug mode to debug java application that runs on Alibaba K8s cluster.

Recommended Way

1. Install kubectl, get kubeconfig and write to file ~/.kube/config, then we can get the cluster information by command $ kubectl cluster-info

    $ curl -LO https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/windows/amd64/kubectl.exe
   

2. From IDEA, create remote debug attaching to localhost:<port>, you will get JDK5~8 command line arguments -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=9090

3. Update Dockerfile to add arguments

    FROM openjdk:8-jdk-alpine
   
    ARG JAVA_ENABLE_DEBUG=false
    ENV JAVA_ENABLE_DEBUG ${JAVA_ENABLE_DEBUG}
   
    ADD ./dockerdemo-0.0.1-SNAPSHOT.jar demo.jar
   
    ENTRYPOINT if [ "${JAVA_ENABLE_DEBUG}" = "true" ]; then \
                   java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=9090 -Djava.security.egd=file:/dev/./urandom -jar /demo.jar; \
               else \
                   java -Djava.security.egd=file:/dev/./urandom -jar /demo.jar; \
               fi
   
    EXPOSE 8080
   

4. Update K8s Pod yaml file and add JAVA_ENABLE_DEBUG as true

    ports:
      - containerPort: 5000
         protocol: TCP
      - containerPort: 9090
         name: jvm-debug
         protocol: TCP
   

   

5. Getting pod status by $ kubectl get pod [-o wide], and forward local port to remote port by running $ kubectl port-forward <pod> <localpot>:<remoteport>

6. Run remote debug from IDEA, the message Connected to the target VM, address: 'localhost:9090', transport: 'socket' means we can debug from IDEA now.

Another Way

1. open project configuration

2. add remote debug

3. made the settings as marked by yellow Host & Port is the IP address of the service external endpoints in k8s.

4. get the "Command Line arguments for remote JVM" in above screenshot and put into your Dockerfile as below: CMD ["java","-jar","-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5000","-Djava.security.egd=file:/dev/./urandom","/devcockpitsvc-3.0.5.jar"]

5. build docker image and deploy.

6. (might needs)restart service in k8s

   

   

   to restart service need to kill it

   

7. start the remote debug task when your service starts to run, and you will see connected: