Jenkins Architecture Fundamentals

Jenkins Architecture Fundamentals

Core Architecture Components

Master Server Architecture

Key Components

  1. Jenkins Web Interface
    • Dashboard and job management
    • Configuration interface
    • Plugin management console
    • System monitoring views
  2. Build Executor
    • Job scheduling system
    • Resource allocation
    • Queue management
    • Load balancing
  3. Plugin System
    • Core plugin architecture
    • Plugin lifecycle management
    • Extension points
    • Plugin dependencies

Agent Architecture

Agent Types

  1. Static Agents
    • Permanent connection to master
    • Dedicated resources
    • Consistent environment
    • Ideal for stable workloads
  2. Dynamic Agents
    • Cloud-based provisioning
    • On-demand scaling
    • Resource optimization
    • Cost-effective for variable loads

Agent Communication

graph TD
    A[Master] -->|JNLP/SSH| B[Agent 1]
    A -->|JNLP/SSH| C[Agent 2]
    A -->|JNLP/SSH| D[Agent N]

System Requirements

Hardware Requirements

Master Node

  1. Minimum Requirements:
    • CPU: 4 cores
    • RAM: 8GB
    • Disk: 50GB
  2. Recommended Specifications:
    • CPU: 8+ cores
    • RAM: 16GB+
    • Disk: 100GB+ SSD

Agent Nodes

  1. Base Requirements:
    • CPU: 2 cores
    • RAM: 4GB
    • Disk: 20GB
  2. Workload-Specific Sizing:
    # Example resource calculation
    CONCURRENT_BUILDS=5
    RAM_PER_BUILD=2GB
    TOTAL_RAM=$((CONCURRENT_BUILDS * RAM_PER_BUILD + 2))GB
    

Network Requirements

Connectivity

  1. Port Requirements: ```plaintext Jenkins Master:
    • 8080: Web interface (HTTP)
    • 8443: Web interface (HTTPS)
    • 50000: Agent communication
    • 22: SSH (if using SSH agents)

    Agents:

    • Outbound access to master
    • Build-specific ports
    • Container registry ports (if using containers) ```
  2. Firewall Considerations:
    • Allow master-agent communication
    • Configure proxy settings if needed
    • Enable SSL/TLS for secure communication
    • Set up network segmentation

Performance Optimization

JVM Tuning

  1. Memory Settings:
    # Recommended JVM settings
    export JENKINS_JAVA_OPTS="-Xmx4g -Xms2g \
      -XX:+UseG1GC \
      -XX:+ExplicitGCInvokesConcurrent \
      -XX:+ParallelRefProcEnabled \
      -XX:+UseStringDeduplication \
      -XX:+HeapDumpOnOutOfMemoryError"
    
  2. Garbage Collection:
    • Monitor GC logs
    • Adjust heap size based on usage
    • Configure GC algorithm

System Monitoring

  1. Key Metrics:
    • CPU usage
    • Memory consumption
    • Disk I/O
    • Network latency
    • Build queue length
  2. Monitoring Tools: ```yaml

    Prometheus configuration

    scrape_configs:

    • job_name: ‘jenkins’ metrics_path: ‘/prometheus’ static_configs:
      • targets: [‘jenkins:8080’] ```

Troubleshooting Guide

Common Issues

  1. Memory Issues:
    # Check memory usage
    jmap -heap <jenkins_pid>
       
    # Analyze heap dump
    jhat jenkins_heap.hprof
    
  2. Performance Problems:
    • Review system logs
    • Check resource utilization
    • Analyze build history
    • Monitor plugin performance
    • Master-agent communication
    • Source control access
    • Artifact repository access
    • Container registry access

Scaling Considerations

Vertical Scaling

Master Node Scaling

  1. CPU Optimization:
    • Monitor build queue
    • Track system load
    • Analyze GC behavior
    • Optimize thread pools
  2. Memory Management:
    // Example JVM settings
    JAVA_OPTS="-Xmx4g -Xms4g -XX:+UseG1GC"
    

Horizontal Scaling

Agent Pool Management

  1. Static Pool:
    // Jenkinsfile example
    pipeline {
      agent {
        label 'high-cpu'
      }
      stages {
        // Pipeline stages
      }
    }
    
  2. Dynamic Scaling: ```yaml

    Kubernetes agent example

    apiVersion: v1 kind: Pod metadata: labels: type: jenkins-agent spec: containers:

    • name: maven image: maven:3.8.4 ```

Data Storage Strategy

File System Storage

Directory Structure

/var/jenkins_home/
├── jobs/                 # Job configurations
├── plugins/              # Installed plugins
├── secrets/             # Security credentials
├── nodes/               # Agent configurations
└── workspace/           # Build workspaces

Backup Strategy

Critical Data

  1. Configuration Files:
    # Backup script example
    tar czf jenkins_backup.tar.gz \
      /var/jenkins_home/jobs \
      /var/jenkins_home/plugins \
      /var/jenkins_home/secrets
    
  2. Job History:
    • Build logs
    • Artifacts
    • Test results
    • Coverage reports

Performance Optimization

Build Optimization

Pipeline Optimization

  1. Parallel Execution:
    parallel {
      stage('Unit Tests') {
        steps { /* test steps */ }
      }
      stage('Integration Tests') {
        steps { /* test steps */ }
      }
    }
    
  2. Resource Management:
    • Workspace cleanup
    • Artifact management
    • Cache utilization

System Tuning

JVM Optimization

  1. Memory Settings:
    export JAVA_OPTS="-Xmx4g -Xms4g \
      -XX:+UseG1GC \
      -XX:+DisableExplicitGC \
      -XX:+AlwaysPreTouch"
    
  2. Garbage Collection:
    • Monitor GC logs
    • Adjust collection strategy
    • Optimize heap size

Hands-on Exercise

Basic Setup

  1. Install Jenkins Master:
    # Ubuntu/Debian
    wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add -
    sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'
    sudo apt update
    sudo apt install jenkins
    
  2. Configure System Resources:
    # Edit Jenkins service file
    sudo systemctl edit jenkins
       
    # Add resource limits
    [Service]
    LimitNOFILE=8192
    Environment="JAVA_OPTS=-Xmx2g -Xms2g"
    

Agent Configuration

  1. Create Static Agent:
    # On agent machine
    mkdir -p /var/jenkins_agent
    wget http://jenkins-master:8080/jnlpJars/agent.jar
    java -jar agent.jar -jnlpUrl http://jenkins-master:8080/computer/agent1/slave-agent.jnlp
    
  2. Test Agent Connection:
    • Create test job
    • Assign to new agent
    • Verify execution

Additional Resources