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CJE: Pipelines and Pipeline as Code

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Pipelines and Pipeline as Code

What this domain covers

The heaviest domain by question weight. You must read and write both syntaxes, know the declarative directive set, and understand shared libraries, sandboxing, and durability.

Core rules

  • Two syntaxes. Scripted pipeline is Groovy: node { stage('Build') { sh 'make' } }. Declarative pipeline has a fixed shape: pipeline { agent any; stages { stage('x') { steps { … } } }; post { … } }. Declarative is a DSL; Groovy-only logic goes inside script { }.
  • Directives: agent, environment, options, parameters, triggers, tools, stages, post, when, input, matrix, libraries. agent none at the top lets each stage pick its own agent.
  • post conditions: always, success, failure, unstable, aborted, changed, fixed, regression, unsuccessful, cleanup. cleanup runs last - the right place for cleanWs().
  • when conditions: branch, tag, buildingTag, changeRequest, changeset, changelog, environment, equals, expression, triggeredBy, not/allOf/anyOf, plus the modifiers beforeAgent, beforeInput, beforeOptions.
  • options: buildDiscarder(logRotator(numToKeepStr:'20')), timeout(time:30, unit:'MINUTES'), retry(3), timestamps(), disableConcurrentBuilds(), skipDefaultCheckout(), skipStagesAfterUnstable(), parallelsAlwaysFailFast(), durabilityHint('PERFORMANCE_OPTIMIZED').
  • Durability. The default PERFORMANCE_OPTIMIZED persists pipeline state after each step so a restart can resume; MAX_SURVIVABILITY writes more often, NONE least.
  • Shared libraries. Configure under Manage Jenkins → System → Global Pipeline Libraries, then @Library('ci-lib@main') _ in scripted or libraries { lib('ci-lib') } in declarative. Layout: vars/ for global steps (vars/buildApp.groovy), src/ for classes, resources/ for libraryResource. Trusted libraries run outside the sandbox.

Worked example

A release stage must run only for tag builds and must fail fast on a failing smoke test. Put options { timeout(time: 15, unit: 'MINUTES') } at pipeline level and when { buildingTag() } on the stage. Reasoning: buildingTag() is true when the build was caused by a tag, whereas tag 'v*' pattern-matches the tag name - different conditions. A failing sh aborts the stage and triggers post { failure { … } }.

Traps

Putting node inside declarative steps; using return instead of returnStatus: true to capture an exit code; assuming Replay persists (edits vanish unless committed); expecting post { failure } to fire for aborted builds; stepping outside the sandbox inside script blocks and then hitting script approval.