JENKINS_HOME environment variable used for 2 conflicting purposes

StackOverflow https://stackoverflow.com/questions/21819382

  •  12-10-2022
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Question

It appears that Jenkins is using the environment variable $JENKINS_HOME for 2 different purposes, and for each purpose it will get a different value.

Purpose#1: First, there is the JENKINS_HOME that is a directory on the local file system that stores files that Jenkins creates. Jenkins uses this directory for disk space to perform builds and keep archive. So a sample value might be:

export JENKINS_HOME=/var/jenkins

That purpose is described here:

Purpose#2: There is another instance where Jenkins used the JENKINS_HOME environment variable, and that is for monitoring external jobs. But this time JENKINS_HOME is a URL, like such:

export JENKINS_HOME=http://user:pw@myserver.acme.org/path/to/jenkins/

That purpose is described here:

So it seems odd that Jenkins would use the same environment variable, yet its value will change depending on the purpose. I would think that the external job would use another name for the environment variable, like JENKINS_URL. I suppose as a workaround I can just set the environment variable in the Servlet container (Tomcat for me) instead of on the operating system, so there is no conflict. Still though, the fact that this conflict for the variable exists in the first place seems strange. Is there something I'm missing?

Was it helpful?

Solution

That is pretty confusing, but the second purpose is for monitoring Jenkins jobs in an external process, not within Jenkins itself; so it's not Jenkins that is using the $JENKINS_HOME value in this case and there is no conflict. They could have picked a better name for the variable, though.

In most other cases, the Jenkins master URL is referred to as JENKINS_URL - see the Jenkins CLI documentation for example.

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