Why is Jenkins.get().getRootUrl() not available when generating DSL? - jenkins-pipeline

Question

I'm debugging a problem with atlassian-bitbucket-server-integration-plugin. The behavior occurs when generating a multi-branch pipeline job, which requires a Bitbucket webhook. The plugin works fine when creating the pipeline job from the Jenkins UI. However, when using DSL to create an equivalent job, the plugin errors out attempting to create the webhook.
I've tracked this down to a line in RetryingWebhookHandler:
String jenkinsUrl = jenkinsProvider.get().getRootUrl();
if (isBlank(jenkinsUrl)) {
throw new IllegalArgumentException("Invalid Jenkins base url. Actual - " + jenkinsUrl);
}
The jenkinsUrl is used as the target for the webhook. When the pipeline job is created from the UI, the jenkinsUrl is set as expected. When the pipeline job is created by my DSL in a freeform job, the jenkinsUrl is always null. As a result, the webhook can't be created and the job fails.
I've tried various alternative ways to get the Jenkins root URL, such as static references like Jenkins.get().getRootUrl() and JenkinsLocationConfiguration.get().getUrl(). However, all values come up empty. It seems like the Jenkins context is not available at this point.
I'd like to submit a PR to fix this behavior in the plugin, but I can't come up with anything workable. I am looking for suggestions about the root cause and potential workarounds. For instance:
Is there something specific about the way my freeform job is executed that could cause this?
Is there anything specific to the way jobs are generated from DSL that could cause this?
Is there another mechanism I should be looking at to get the root URL from configuration, which might work better?
Is it possible that this behavior points to a misconfiguration in my Jenkins instance?
If needed, I can share the DSL I'm using to generate the job, but I don't think it's relevant. By commenting out the webhook code that fails, I've confirmed that the DSL generates a job with the correct config.xml underneath. So, the only problem is how to get the right configuration to the plugin so it can set up the webhook.

Answer 1

It turns out that this behavior was caused by a partial misconfiguration of Jenkins.
While debugging problems with broken build links in Bitbucket (pointing me at unconfigured-jenkins-location instead of the real Jenkins URL), I discovered a yellow warning message on the front page of Jenkins which I had missed before, telling me that the root server URL was not set:
Jenkins root URL is empty but is required for the proper operation of many Jenkins features like email notifications, PR status update, and environment variables such as BUILD_URL.
Please provide an accurate value in Jenkins configuration.
This error message had a link to Manage Jenkins > Configure System > Jenkins Location. The correct Jenkins URL actually was set there (I had already double-checked this), but the system admin email address in the same section was not set. When I added a valid email address, the yellow warning went away.
This change fixed both the broken build URL in BitBucket, as well as the problems with my DSL. So, even though it doesn't make much sense, it seems like the missing system admin email address was the root cause of this behavior.