Debug Spring Boot Apps on Red Hat OpenShift4

3 min readSep 30, 2020

This story begins with a question from an OpenShift user about how to debug a Spring Boot application that runs as a container in OpenShift. Considering that quite a lot of coder friends use this framework as a microservice application, so I tried to make a tutorial for remote debugging java applications on OpenShift4.

Below picture shows this tutorial flow

Prerequisite

Preinstalled OpenShift Container Platform 4 (OCP4)
OpenShift client command line tools (oc tools) atau k8s cli. Download here.
Your favorite IDE. Publisher uses Red Hat CodeReady Studio (Eclipse based) and VSCode for this tutorial.
Deploy your Springboot apps on OpenShift (sample apps on GitHub). This time i use s2i method on OpenShift web console.

Step 1 : Set Debug Mode as Environment Variable

Add new environment variable JAVA_DEBUG=true on your Deployment or DeploymentConfig. Below picture use OpenShift web console to add environment variable.

Or, using oc or kubectl command line below:

$ kubectl set env deployment/springboot-sample-apps-git JAVA_DEBUG=true

on startup log, find below information for debug port.

Listening for transport dt_socket at address: 5005

Note: s2i java use port 5005 as default debug port. it might different based on your preferred base image.

Step 2 : Port Forward Debug port to Your Local Machine

find running pods on your namespace:

$ kubectl get pods | grep Running....springboot-sample-apps-git-XXXX   1/1       Running

Port forward the debug port on target pod

$ kubectl port-forward springboot-sample-apps-git-XXXX 5005:5005....Forwarding from 127.0.0.1:5005 -> 5005
Forwarding from [::1]:5005 -> 5005

Step 3 : Setup Remote Debug on Your IDE

Go to Debug Configuration > Remote Java Application

Connection Type: Standard (Socket Attach)

Host: localhost

Port: 5005

if you use VSCode, add below configuration launch.json on .vscode folder.

{   "version": "0.2.0",   "configurations": [      {         "type": "java",         "name": "Debug (Attach)",         "projectName": "springboot-sample-apps",         "request": "attach",         "hostName": "localhost",         "port": 5005      }
   ]}