Jenkinsfile Generator Skill

Generate production-ready Jenkinsfiles following best practices. All generated files are validated using devops-skills:jenkinsfile-validator skill.

Philosophy

• Prefer Declarative syntax; reach for Scripted only when full Groovy control is genuinely needed.
• Never hardcode secrets: bind credentials through the Jenkins Credentials Store.
• Generate from the templates and best-practice references, then validate before presenting.
• Fail fast and clean up: set timeouts, fail-fast on parallel blocks and always clean the workspace.

When to Use

• Creating a new Jenkins pipeline script, Groovy pipeline or build configuration
• Adding parallel or matrix builds, parameters, or manual approval stages to a Jenkins setup
• Adding Docker or Kubernetes agents and deployments to a pipeline
• Adding DevSecOps stages such as SonarQube, OWASP Dependency-Check or Trivy
• Scaffolding a Jenkins shared library

When Not to Use

• Validating or linting an existing Jenkinsfile (use the Jenkinsfile validator skill instead)
• Writing CI configuration for other systems such as GitHub Actions, GitLab CI or Azure Pipelines
• Debugging a failed build from its console logs rather than the pipeline definition
• Configuring Jenkins controller settings, plugins installation or job folders outside the Jenkinsfile

Core Capabilities

1. Declarative Pipelines (RECOMMENDED)

Process:

1. Consult assets/templates/declarative/basic.Jenkinsfile and references/best_practices.md
2. Generate with required elements:
   • Stages with descriptive names
   • Environment block with credentials binding (never hardcode secrets)
   • Options: timeout, buildDiscarder, timestamps, disableConcurrentBuilds
   • Post conditions: always (cleanup), success (artifacts), failure (notifications)
   • Always add parallelsAlwaysFailFast() in options when using parallel blocks
   • Always include fingerprint: true when using archiveArtifacts
3. ALWAYS validate using devops-skills:jenkinsfile-validator skill

2. Scripted Pipelines

Use for complex conditional logic, dynamic generation, or full Groovy control.

Process:

1. Consult assets/templates/scripted/basic.Jenkinsfile
2. Implement try-catch-finally for error handling
3. ALWAYS validate using devops-skills:jenkinsfile-validator skill

3. Parallel/Matrix Pipelines

Use parallel {} or matrix {} with axes {} for multi-dimensional builds. See Parallel & Matrix for failFast configuration.

4. Security Scanning (DevSecOps)

Add SonarQube, OWASP Dependency-Check, Trivy stages with fail thresholds.

5. Shared Library Scaffolding

python3 scripts/generate_shared_library.py --name my-library --package org.example

Declarative Syntax Reference

Agent Types

agent any                                    // Any available agent
agent { label 'linux && docker' }           // Label-based
agent { docker { image 'maven:3.9.11-eclipse-temurin-21' } }
agent { kubernetes { yaml '...' } }         // K8s pod template
agent { kubernetes { yamlFile 'pod.yaml' } } // External YAML

Environment & Credentials

environment {
    VERSION = '1.0.0'
    AWS_KEY = credentials('aws-key-id')     // Creates _USR and _PSW vars
}

Options

options {
    buildDiscarder(logRotator(numToKeepStr: '10'))
    timeout(time: 1, unit: 'HOURS')
    disableConcurrentBuilds()
    timestamps()
    parallelsAlwaysFailFast()
    durabilityHint('PERFORMANCE_OPTIMIZED')  // 2-6x faster for simple pipelines
}

Parameters

parameters {
    string(name: 'VERSION', defaultValue: '1.0.0')
    choice(name: 'ENV', choices: ['dev', 'staging', 'prod'])
    booleanParam(name: 'SKIP_TESTS', defaultValue: false)
}

When Conditions

Add beforeAgent true to skip agent allocation if condition fails.

Error Handling

catchError(buildResult: 'UNSTABLE', stageResult: 'FAILURE') { sh '...' }
warnError('msg') { sh '...' }      // Mark UNSTABLE but continue
unstable(message: 'Coverage low')   // Explicit UNSTABLE
error('Config missing')             // Fail without stack trace

Post Section

post {
    always { junit '**/target/*.xml'; cleanWs() }
    success { archiveArtifacts artifacts: '**/*.jar', fingerprint: true }
    failure { slackSend color: 'danger', message: 'Build failed' }
    fixed { echo 'Build fixed!' }
}

Order: always → changed → fixed → regression → failure → success → unstable → cleanup

Always use fingerprint: true with archiveArtifacts for build traceability.

Parallel & Matrix

Always add parallelsAlwaysFailFast() to pipeline options {} block: covers all parallel/matrix blocks automatically. Use per-block failFast true only when options-level is not set:

// Per-block alternative (when options-level not set)
stage('Tests') {
    failFast true
    parallel {
        stage('Unit') { steps { sh 'npm test:unit' } }
        stage('E2E') { steps { sh 'npm test:e2e' } }
    }
}

stage('Matrix') {
    matrix {
        axes {
            axis { name 'PLATFORM'; values 'linux', 'windows' }
            axis { name 'BROWSER'; values 'chrome', 'firefox' }
        }
        excludes { exclude { axis { name 'PLATFORM'; values 'linux' }; axis { name 'BROWSER'; values 'safari' } } }
        stages { stage('Test') { steps { echo "Testing ${PLATFORM}/${BROWSER}" } } }
    }
}

Input (Manual Approval)

stage('Deploy') {
    input { message 'Deploy?'; ok 'Deploy'; submitter 'admin,ops' }
    steps { sh './deploy.sh' }
}

Place input outside steps to avoid holding agents.

Scripted Syntax Reference

node('agent-label') {
    try {
        stage('Build') { sh 'make build' }
        stage('Test') { sh 'make test' }
    } catch (Exception e) {
        currentBuild.result = 'FAILURE'
        throw e
    } finally {
        deleteDir()
    }
}

// Parallel
parallel(
    'Unit': { node { sh 'npm test:unit' } },
    'E2E': { node { sh 'npm test:e2e' } }
)

// Environment
withEnv(['VERSION=1.0.0']) { sh 'echo $VERSION' }
withCredentials([string(credentialsId: 'key', variable: 'KEY')]) { sh 'curl -H "Auth: $KEY" ...' }

NonCPS Annotation

@NonCPS
def parseJson(String json) {
    new groovy.json.JsonSlurper().parseText(json)
}

Required for non-serializable operations (JsonSlurper, iterators, regex Matchers). No pipeline steps inside.

Docker & Kubernetes

Docker Agent

agent { docker { image 'maven:3.9.11'; args '-v $HOME/.m2:/root/.m2'; reuseNode true } }

Build & Push

def img = docker.build("myapp:${BUILD_NUMBER}")
docker.withRegistry('https://registry.example.com', 'creds') { img.push(); img.push('latest') }

Kubernetes Pod

agent {
    kubernetes {
        yaml '''
apiVersion: v1
kind: Pod
spec:
  containers:
  - name: maven
    image: maven:3.9.11-eclipse-temurin-21
    command: [sleep, 99d]
'''
    }
}
// Use: container('maven') { sh 'mvn package' }

Shared Libraries

@Library('my-shared-library') _
// or dynamically: library 'my-library@1.0.0'

// vars/log.groovy
def info(msg) { echo "INFO: ${msg}" }

// Usage
log.info 'Starting build'

Validation Workflow

ALWAYS validate using devops-skills:jenkinsfile-validator skill:

1. Generate Jenkinsfile
2. Invoke devops-skills:jenkinsfile-validator skill
3. Handle validation results by severity:
   • ERRORS: Must fix - these break the pipeline
   • WARNINGS: Should fix - indicate potential issues
   • INFO: Apply optimizations based on use case (failFast, build triggers, etc.)
4. Re-validate after fixes
5. Present validated Jenkinsfile to user

Validation commands:

# Full validation (syntax + security + best practices)
bash scripts/validate_jenkinsfile.sh Jenkinsfile

# Syntax only (fastest)
bash scripts/validate_jenkinsfile.sh --syntax-only Jenkinsfile

Generator Scripts

Use for simple, standard pipelines. Use manual generation for complex pipelines with custom logic or non-standard requirements.

# Declarative (simple pipelines)
python3 scripts/generate_declarative.py --output Jenkinsfile --stages build,test,deploy --agent docker

# Scripted (simple pipelines)
python3 scripts/generate_scripted.py --output Jenkinsfile --stages build,test --agent label:linux

# Shared Library (always use script for scaffolding)
python3 scripts/generate_shared_library.py --name my-library --package com.example

Plugin Documentation Lookup

Always consult external docs for:

• Plugins NOT in references/common_plugins.md
• Version-specific documentation
• Complex configurations or advanced options

Skip external lookup when:

• Using basic syntax from references/common_plugins.md
• Simple, well-documented steps (e.g., sh, checkout scm, junit)

Covered plugins: Git, Docker, Kubernetes, Credentials, JUnit, Slack, SonarQube, OWASP Dependency-Check, Email, AWS, Azure, HTTP Request, Microsoft Teams, Nexus, Artifactory, GitHub

Anti-Patterns

NEVER use Scripted Pipeline for new work

WHY: Declarative Pipeline syntax is the current standard with better tooling and cleaner validation; Scripted Pipeline should only be used to maintain existing files or when full Groovy control is required.

BAD: New pipelines starting with node { ... }.

GOOD: Start with pipeline { agent any stages { ... } } Declarative syntax.

NEVER store credentials as plain text pipeline parameters

WHY: Pipeline parameters are logged and visible in the Jenkins UI; credentials must go through the Jenkins Credentials Store.

BAD: parameters { string(name: 'API_KEY', ...) }

GOOD: withCredentials([string(credentialsId: 'api-key-prod', variable: 'API_KEY')]) { ... }

NEVER run all stages on a heavyweight executor without parallelism

WHY: Sequential stages on a single executor waste build time; extract independent stages into parallel { } blocks.

BAD: Lint, unit-test, integration-test, and SAST in sequential stages.

GOOD: Wrap independent stages in parallel { stage('Lint') { ... } stage('Unit Test') { ... } }.

NEVER omit post { always { cleanWs() } }

WHY: Without workspace cleanup, Jenkins agents fill disk with build artifacts from previous runs, causing disk-full build failures.

BAD: No post block in the pipeline.

GOOD: post { always { cleanWs() } } in every Declarative pipeline.

NEVER call sh with inline secret variable expansion

WHY: Shell substitution expands secrets into the command string where they appear in build logs and process lists.

BAD: sh "curl -H 'Authorization: Bearer ${API_KEY}'"

GOOD: withCredentials([...]) { sh 'curl -H "Authorization: Bearer $API_KEY"' } (single quotes prevent Groovy expansion; the credential is still available via the environment).

NEVER use parallel blocks without fail-fast

WHY: Without fail-fast, the remaining parallel branches keep running after one has failed, wasting agent time on a build that is already lost.

BAD: A parallel { ... } block with no parallelsAlwaysFailFast() in options and no failFast true.

GOOD: Add parallelsAlwaysFailFast() to the pipeline options {} block.

NEVER archive artifacts without fingerprinting

WHY: Fingerprints give build traceability, linking an artifact back to the build that produced it.

BAD: archiveArtifacts artifacts: '**/*.jar'

GOOD: archiveArtifacts artifacts: '**/*.jar', fingerprint: true

NEVER present a generated Jenkinsfile without validating it

WHY: Generation can produce syntax errors or best-practice violations. The workflow requires validation with the Jenkinsfile validator skill and a re-run after fixes.

BAD: Generate a Jenkinsfile and hand it straight to the user.

GOOD: Run bash scripts/validate_jenkinsfile.sh Jenkinsfile, fix ERRORS and WARNINGS, re-validate, then present it.

NEVER omit timeouts from pipeline options

WHY: Without a timeout a hung build occupies an executor indefinitely.

BAD: An options {} block with no timeout(...), or no options at all.

GOOD: options { timeout(time: 1, unit: 'HOURS') }

NEVER place input inside steps

WHY: An input inside steps holds an agent while it waits for approval. Declaring it at stage level avoids that.

BAD: Calling input within a stage's steps block while an agent is allocated.

GOOD: stage('Deploy') { input { message 'Deploy?' } steps { sh './deploy.sh' } }

References

// Minimal Declarative Pipeline
pipeline {
    agent any
    stages {
        stage('Build') { steps { sh 'make' } }
        stage('Test') { steps { sh 'make test' } }
    }
}

// Error-tolerant stage
stage('Flaky Tests') {
    steps {
        catchError(buildResult: 'SUCCESS', stageResult: 'UNSTABLE') {
            sh 'run-flaky-tests.sh'
        }
    }
}

// Conditional deployment with approval
stage('Deploy') {
    when { branch 'main'; beforeAgent true }
    input { message 'Deploy to production?' }
    steps { sh './deploy.sh' }
}

• references/best_practices.md - Performance, security, reliability patterns
• references/common_plugins.md - Git, Docker, K8s, credentials, notifications
• assets/templates/ - Declarative and scripted templates
• devops-skills:jenkinsfile-validator skill - Syntax and best practices validation

Always prefer Declarative unless scripted flexibility is required.