How to trigger a Jenkins job automatically from a GitHub PR

Two words answer is GitHub Webhook. For a detailed answer, keep reading.

In case you are not familiar with Webhooks, they are like reverse APIs where the application supporting the Webhook is sending a POST request to an endpoint with the details of the event in the payload. I recommend watching some YouTube videos about Webhooks if you are not familiar with them.

Now, coming back to the topic of the post, GitHub Webhook sends a notification to an external web server whenever a certain event happens in the repository or organization.

Let’s assume we want to trigger a Jenkins job that runs unit test cases whenever the developer opens/reopens/adds more commits to a PR.

1. Install Generic Webhook Trigger plugin in Jenkins.

And add this block in your scripted Jenkinsfile:

triggers {
   GenericTrigger(
      genericVariables: [
             [ key: 'action',  value: '$.action'],
             [ key: 'draft_pr', value: '$.pull_request.draft'],
             [ key: 'pr_url', value: '$.pull_request.html_url'], 
             [ key: 'git_sha_statuses_url', value:
         '$.pull_request.statuses_url']      
      ],
      causeString: 'Triggered from PR: $pr_url
      token: '<some-random-string>',
      printContributedVariables: true,
      printPostContent: true…