I watched an entire Jenkins video series and understood almost none of it. The moment
Groovy appeared, I zoned out, convinced I needed to learn a programming language to do this
job. I was wrong, and figuring out why unlocked everything.
By the end I had a pipeline that, from one git push, computes the version, lints, tests,
builds a Docker image, pushes it to a registry, deploys it, verifies it, and tags the
release. Automatically.
The fear-buster
A Jenkinsfile is a fill-in-the-blanks form, not a language. The structure
pipeline { stages { stage { steps { } } } } is fixed. You fill in stage names and shell
commands you already know. That is it.
Two servers
A Jenkins server (the factory, runs the pipeline) and an app server (the shop, runs the
app). Jenkins builds and ships; it never runs the app.
Jenkins on its own server.
Secrets in a vault
Every secret (SSH key, server IP, Docker Hub token, GitHub token) lives in Jenkins'
credential store with a label. The Jenkinsfile references the label, never the secret.
Secrets referenced by label.
Eight stages
Checkout, Compute Version, Lint, Test, Build and Push, Deploy, Verify, Tag Release. Runs
top to bottom, stops on any failure so broken code never deploys.
A full run, every stage green.
The webhook makes it automatic
A doorbell: GitHub pings Jenkins on every push, so the pipeline runs on its own. I opened
Jenkins only to GitHub's webhook IP ranges, not the whole internet.
A build that started itself after a push.
Multibranch and PR checks
Every branch and pull request builds automatically, and the PR shows a pass/fail check on
GitHub. Deploy runs only on main, so feature branches are tested but never shipped.
The check stamped on the pull request.
Shared library
The build-and-push logic lives in a separate repo. The Jenkinsfile calls it in one line.
Fix once, every project gets the fix.
Calling the shared function.
Dynamic versioning
A feat: commit bumps the minor version, a fix: bumps the patch. The pipeline reads
the commit and tags the release. No human picks a version.
feat produced v0.1.0, fix produced v0.1.1.
The bugs that taught me most
Cloud account suspended mid-build (rebuilt on a new provider, faster the second time).
Deleted my SSH keys with a careless command. Jenkins refusing to start on the wrong Java
version. A stage hanging because my lint command started a never-ending server. A first run
failing on a missing tool. Every one was a real lesson.
Takeaway
Jenkins is a form, not a language. The full code and screenshots:
https://github.com/vivianokose/nexaops-operations-lab/tree/main/08-jenkins
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