Debugging Camel K Integrations

Sometimes integrations can fail or behave unexpectedly for unknown reasons and a developer needs to investigate the cause of such behavior. Attaching a Java debugger to an integration is a common way to start the investigation.

Even if Camel K integrations run on a Kubernetes cluster, it’s very easy to attach a Java debugger to the remote integration using the CLI.

If you’re a VS Code user, you can watch this video.

Find below a more generic explanation using IntelliJ.

Suppose you just launched an integration using the following command:

kamel run examples/Sample.java

An integration named sample should be running in the cluster. You can use the kamel debug command to put it in "debug mode".

kamel debug sample

A possible output that you may find is the following:

$ kamel debug sample
Enabling debug mode on integration "sample"...
[1] Monitoring pod sample-8455c8b985-5cxvc
[1] exec java -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:5005 -cp ./resources:[..omitted..] io.quarkus.runner.GeneratedMain
[1] Listening for transport dt_socket at address: 5005
Forwarding from 127.0.0.1:5005 -> 5005
Forwarding from [::1]:5005 -> 5005

As you can see in the logs, the CLI has configured the integration in debug mode (see option -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:5005) and started forwarding the local port 5005 on the workstation machine (local port can be changed using the --port option) to the container port 5005, where the JVM is waiting for a debugger.

The JVM is suspended and waits for a debugger to attach by default: this behavior can be turned off using the --suspend=false option.

Last thing to do is, with your IDE opened on the integration file (if using Java, Groovy or Kotlin), the Apache Camel project or the Camel K Runtime project, to start a remote debugger on localhost:5005.

The following picture shows the configuration of a remote debugger in IntelliJ Idea.

Configuration of the remote debugger in IntelliJ Idea

Once you configure a debugger, you can add breakpoints to various part of the code, then connect the debugger to trigger the JVM startup.

When the debugging session is finished, hitting ctrl+c on the terminal where the kamel CLI is running will restore the integration to its original status.

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