This guide explores a Jenkins server implementation that demonstrates enterprise-level infrastructure automation using Terraform, AWS Auto Scaling Groups, and Application Load Balancers for a scalable CI/CD platform.

Table of Contents

Architecture Overview

The Jenkins server implementation follows a modular, security-first approach that combines multiple AWS services to create a scalable and resilient CI/CD infrastructure:

Internet → ALB (SSL Termination) → Target Group → Auto Scaling Group → Jenkins Instance (Private) → EBS Volumes (Encrypted)

Core Components

Auto Scaling Group: Single-instance configuration with automatic recovery capabilities for cost-effective high availability.

Application Load Balancer: SSL termination and traffic distribution while maintaining private instance placement.

EBS Storage: Dedicated encrypted volumes for Jenkins data persistence and compliance requirements.

Security Groups: Multi-layer security controls for network traffic isolation and access management.

Key Features and Implementation

Auto Scaling Group Integration

module "jenkins_server_asg" {
  source = "./jenkins-aws"
  
  instance_type = var.instance_type
  min_size = 1
  max_size = 1
  desired_capacity = 1
  health_check_type = "ELB"
  health_check_grace_period = var.health_check_grace_period
}

This approach provides several benefits:

  • Automatic Recovery: ELB health checks ensure failed instances are replaced
  • Cost Efficiency: Single-instance design minimizes infrastructure costs
  • High Availability: ASG ensures service continuity during failures

Application Load Balancer Configuration

module "alb" {
  source = "./alb-aws"
  
  is_internal_alb = true
  ssl_policy = var.ssl_policy
  certificate_domain_name = var.domain_name
}

This configuration provides:

  • SSL Termination: Centralized certificate management and encryption
  • Private Networking: Jenkins instances remain in private subnets
  • Load Distribution: Ready for multi-instance scaling when needed

Security Implementation

Security forms the foundation of this Jenkins deployment with multiple layers of protection:

Network Security

  • Private Instance Placement: Jenkins instances receive no public IP addresses
  • Internal ALB Configuration: Load balancer operates within the VPC boundary
  • Security Group Isolation: Controlled traffic flow between ALB and Jenkins instances
  • CIDR-Based Access Control: Configurable source IP restrictions

Encryption at Rest

resource "aws_ebs_volume" "jenkins_data" {
  encrypted = true
  kms_key_id = var.kms_id
  size = var.ebs_volume_size
}

Both root and additional EBS volumes implement encryption by default, ensuring data protection for Jenkins configurations, build artifacts, and logs.

SSL/TLS Configuration

The implementation supports SSL policies with configurable certificate management:

  • Default SSL Policy: ELBSecurityPolicy-TLS-1-1-2017-01
  • ACM Integration: Automatic certificate validation and renewal
  • HTTPS Redirection: Optional HTTP to HTTPS traffic redirection

High Availability Design

Despite using a single instance configuration, the implementation incorporates several high availability features:

Automatic Recovery

target_group_arns = [aws_lb_target_group.jenkins_target_group.arn]
health_check_type = "ELB"
health_check_grace_period = var.health_check_grace_period

The Auto Scaling Group monitors instance health through ELB health checks and automatically replaces failed instances, ensuring minimal downtime.

Graceful Deployment

  • Batch Deployment: Controlled instance replacement during updates
  • Deregistration Delays: Configurable target group deregistration for in-flight request completion
  • Health Check Validation: Multiple health check attempts before marking instances as healthy

Configuration Management

The implementation provides extensive customization through configurable variables covering all aspects of the deployment:

Infrastructure Variables Examples

variable "instance_type" {
  description = "The Jenkins server instance type"
  type = string
  default = "t2.micro"
}

variable "jenkins_port" {
  description = "The Jenkins server port"
  type = number
  default = 8080
}

Operational Variables

  • Health Check Parameters: Intervals, thresholds, timeouts
  • Deployment Configuration: Batch sizes, update policies
  • Storage Options: Volume sizes, encryption settings, snapshot sources
  • Network Settings: VPC, subnet, security group configurations

Storage and Encryption

The storage architecture supports both development and production workloads:

EBS Volume Configuration

ebs_block_device {
  device_name = "/dev/sda"
  volume_type = var.ebs_type
  volume_size = var.ebs_size
  encrypted = var.ebs_encrypted
  iops = var.ebs_iops
}

Storage Features

  • Dedicated Data Volume: Separate 100GB EBS volume for Jenkins data
  • Snapshot Support: Optional snapshot-based volume creation for data recovery
  • Performance Optimization: Configurable IOPS for high-performance workloads
  • Encryption: KMS-based encryption for compliance requirements

Load Balancing and SSL Termination

The Application Load Balancer provides sophisticated traffic management:

Target Group Configuration

resource "aws_lb_target_group" "jenkins_target_group" {
  name = "${var.name_prefix}-jenkins-tg"
  port = var.jenkins_port
  protocol = "HTTP"
  vpc_id = data.aws_vpc.default.id
  
  health_check {
    enabled = true
    healthy_threshold = var.alb_healthy_threshold
    interval = var.alb_health_check_interval
    matcher = "200"
    path = var.alb_health_check_path
    port = "traffic-port"
    protocol = "HTTP"
    timeout = var.alb_health_check_timeout
    unhealthy_threshold = var.alb_unhealthy_threshold
  }
}

Advanced Health Checking

  • Custom Health Check Path: /login endpoint monitoring
  • Configurable Thresholds: 2 healthy/10 unhealthy checks by default
  • Flexible Intervals: 15-second health check intervals
  • HTTP 200 Validation: Ensures Jenkins application is responding correctly

DNS Integration and Domain Management

Optional Route53 integration provides custom domain support:

DNS Configuration

resource "aws_route53_record" "jenkins_dns" {
  count = var.create_route53_entry ? 1 : 0
  zone_id = var.hosted_zone_id
  name = var.domain_name
  type = "A"
  
  alias {
    name = module.alb.alb_dns_name
    zone_id = module.alb.alb_zone_id
    evaluate_target_health = true
  }
}

This enables domain names for Jenkins instances while maintaining automatic failover capabilities.

Monitoring and Health Checks

Detailed monitoring ensures operational visibility:

Multi-Layer Health Checks

  • ALB Health Checks: Application-level monitoring via /login endpoint
  • ASG Health Checks: Instance-level monitoring through ELB integration
  • CloudWatch Integration: Automatic metric collection and alarming capabilities

Operational Logging

variable "script_log_level" {
  description = "Log level for deployment scripts"
  type = string
  default = "INFO"
}

Configurable logging levels support troubleshooting and operational monitoring.

Production-Ready Features

Several features distinguish this implementation as production-grade:

Security Hardening

  • No Public IP Assignment: Instances remain in private subnets
  • Encryption by Default: All storage encrypted with customer-managed keys
  • SSL Enforcement: TLS policies with optional HTTPS redirection
  • Access Control: Multiple layers of network and application security

Operational Excellence

  • Infrastructure as Code: Complete Terraform automation
  • Modular Design: Reusable components through external Git modules
  • Configuration Management: Extensive variable-based customization
  • Deployment Safety: Controlled rollouts with health verification

Cost Optimization Strategies

The implementation balances functionality with cost considerations:

Development Environment Optimization

  • t2.micro Default: Cost-effective instance type for development
  • Single Instance: Minimal infrastructure footprint
  • Optional Features: DNS and SSL features can be disabled for testing

Production Scaling

  • Instance Type Flexibility: Easy scaling to larger instance types
  • Storage Optimization: Configurable volume sizes and performance
  • Resource Tagging: Cost allocation and management support

Deployment and Operational Considerations

Deployment Process

variable "batch_size" {
  description = "Rolling deployments size"
  type = number
  default = 1
}

Controlled deployment process ensures zero-downtime updates and rollback capabilities.

Maintenance Operations

  • Skip Health Checks: Optional health check bypass for maintenance
  • Graceful Shutdowns: Configurable deregistration delays
  • Backup Integration: Snapshot-based backup and recovery support

Conclusion

This post demonstrates how to build a production-ready Jenkins CI/CD infrastructure that combines AWS best practices with Terraform automation. The architecture provides enterprise-level security, high availability, and operational flexibility while maintaining cost efficiency for development environments.

Key strengths include the modular design using external Git repositories, extensive configuration options, security-first approach with encryption and private networking, and production-ready features like SSL termination and DNS integration. The implementation demonstrates how to build scalable infrastructure that grows with organizational needs while maintaining operational excellence and security compliance.

This pattern serves as an excellent foundation for organizations looking to implement robust CI/CD infrastructure that can scale from development environments to enterprise production workloads.

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