How to Debug Jenkins remotely
Thanks Jenkins Maven HPI Plugin, you can do the most Jenkins plugin development stuff locally. But in some cases, you have to debug a Jenkins instance remotely (In my case, the Jenkins had to run in Azure to reproduce a bug).
Jenkins is a Java application, so you have to add Java's JDWP agent for debugging as Java argument to Jenkins config
The big question is, where is the configuration file on the machine to do it.
Answer: It depends on your operating system 🤓
Fortunately, Cloudbees has a good overview where to find the configuration files depend on the operating system .
In my case, I use Ubuntu as operating system. On Ubuntu, the configuration file is /etc/default/jenkins. I can extend the system environment variable JAVA_ARGS, there (see sample below).
1# defaults for Jenkins automation server
2
3# pulled in from the init script; makes things easier.
4NAME=jenkins
5
6# arguments to pass to java
7
8# Allow graphs etc. to work even when an X server is present
9JAVA_ARGS="-Djava.awt.headless=true"
10
11JAVA_ARGS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:8000"
12
13# more configuration stuff
Then restart your Jenkins instance (sudo service jenkins restart). Then you should see in Jenkins log (default on Ubuntu: /var/log/jenkins/jenkins.log) the following snippet:
Now, you can connect your IDE via Remote Debug to your Jenkins instance.