[Previously published at the now defunct MetaBrite Dev Blog.]
Much of our code is in one large GitHub repository, from which several different applications are built. When changes are pushed to the master branch, we want only the applications in affected directories to be built. This was not easy to get right with “Pipeline script from SCM” builds.
#3 in a series on Jenkins Pipelines
To get builds to trigger upon a push to GitHub, you need to configure a webhook pointing to your Jenkins Master.
Create an SSH key for Jenkins/GitHub. A passphrase is recommended.
- Public Key: Upload the SSH public key to GitHub
- Private Key: Go to Jenkins > Credentials > SSH Username with Private Key. Add the private key with a meaningful ID
- In your AMI, make sure that you’ve run ssh-keyscan -H github.com >> ~/.ssh/known_hosts to prevent Git from asking about the authenticity of github.com
- Do not install the SSH private key into your AMI
In your Jenkins job configuration:
Build Trigger > Build when a change is pushed to GitHub
Pipeline > Definition > Pipeline script from SCM
Repository URL: email@example.com:ORGANIZATION/REPOSITORY.git (the SSH form of the URL, not the HTTPS)
Credentials: the ID of your GitHub SSH credential
To build only when changes affect the /foo and /bar directories of your repository: Additional Behaviors > Polling ignores commits in certain paths > Included Regions:
Script Path: path-to-your-Jenkinsfile
- Use the checkout scm step, not the git step. The former plays well with GitHub polling; the latter doesn’t.
- If you need to clean up your workspace, do not remove the .git directory. Otherwise, you are likely to have unnecessary builds as the Git Plugin doesn’t do polling well without a persistent workspace.
- Do not use sshagent to check out code from GitHub. The SSH credential configured on the Repository URL will be used during checkout scm.