Jenkins

Master continuous integration and deployment with the leading open-source automation server

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What is Jenkins?

Jenkins is an open-source automation server written in Java that enables developers to reliably build, test, and deploy their software. It facilitates Continuous Integration (CI) and Continuous Deployment (CD) by automating the software development lifecycle. Jenkins supports building, deploying, and automating any project through its extensive plugin ecosystem.

Originally developed as "Hudson" in 2004 by Kohsuke Kawaguchi at Sun Microsystems, Jenkins has grown to become one of the most popular DevOps tools. With over 1,800 plugins and a large community, Jenkins can integrate with virtually any tool in the software development and deployment toolchain.

Jenkins Capacity Calculator

8m
Avg Build Time
8
Max Concurrent
1440
Daily Capacity
0m
Avg Queue Time

Memory Needed: 5GB

Disk Space: 65GB

Performance Score: 100/100

Jenkins Core Concepts

Jobs/Projects

Basic units of work in Jenkins that define what actions to perform.

• Freestyle projects
• Pipeline projects
• Multi-configuration
• External job monitoring
• Organizational folders

Builds

Execution instances of jobs with their own workspace and results.

• Build history
• Console output
• Test results
• Artifacts
• Build parameters

Plugins

Extensions that add functionality to Jenkins core platform.

• 1,800+ available plugins
• SCM integrations
• Build tools
• Deployment tools
• Notification systems

Nodes

Machines where Jenkins can execute builds (master and agents).

• Master node (controller)
• Agent nodes (workers)
• Executors per node
• Node labels
• Cloud nodes

Jenkins Pipeline Types

Declarative Pipeline

Structured, opinionated syntax that provides a simplified way to define pipelines.

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

Scripted Pipeline

Groovy-based DSL that provides maximum flexibility for complex scenarios.

Scripted Pipeline Example
node {
  stage('Checkout') {
    checkout scm
  }
  stage('Build') {
    sh 'make build'
  }
  stage('Test') {
    parallel(
      unit: { sh 'make unit-test' },
      integration: { sh 'make integration-test' }
    )
  }
}

Jenkins Build Triggers

SCM Triggers

Automatic builds triggered by source code changes.

• Webhook triggers
• SCM polling
• GitHub/GitLab integration
• Branch-based triggers
• Pull request builds

Time-based Triggers

Scheduled builds using cron-like syntax.

• Cron expressions
• Nightly builds
• Weekly reports
• Maintenance windows
• Load testing schedules

Dependency Triggers

Builds triggered by completion of upstream projects.

• Upstream builds
• Pipeline stages
• Multi-project dependencies
• Conditional triggers
• Parameterized triggers

Manual Triggers

User-initiated builds with optional parameters.

• Build with parameters
• Remote triggers
• API-triggered builds
• Approval workflows
• Emergency deployments

Real-World Jenkins Implementations

Netflix

Uses Jenkins for massive-scale deployment pipeline across thousands of microservices.

  • • 2,500+ Jenkins instances
  • • 150,000+ builds per day
  • • Spinnaker integration
  • • Canary deployments

Samsung

Leverages Jenkins for mobile app CI/CD and firmware development.

  • • Android build automation
  • • Device testing farms
  • • Code quality gates
  • • Release management

LinkedIn

Powers continuous deployment for LinkedIn's platform and services.

  • • Multi-datacenter deployments
  • • A/B testing integration
  • • Performance testing
  • • Rollback automation

NASA JPL

Uses Jenkins for mission-critical software development and testing.

  • • Flight software builds
  • • Simulation testing
  • • Compliance reporting
  • • Security scanning

Jenkins Best Practices

✅ Do

  • • Use Pipeline as Code (Jenkinsfile)
  • • Implement proper error handling and retries
  • • Use agents for build isolation
  • • Archive important artifacts
  • • Monitor build performance metrics
  • • Use parallel execution for faster builds
  • • Implement proper security and access controls

❌ Don't

  • • Run builds on the master node
  • • Store secrets in plain text
  • • Create overly complex pipelines
  • • Ignore build failures
  • • Skip backup strategies
  • • Overcomplicate with too many plugins
  • • Neglect build performance optimization

📝 Jenkins Quiz

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What is Jenkins primarily used for?