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

• Jenkins Architecture Documentation
• Scaling Jenkins
• Jenkins Performance Tuning
• Jenkins Security Best Practices