OpenGSLB

OpenGSLB is an open-source, self-hosted GSLB system for intelligent traffic distribution across multiple data centers and cloud regions. It delivers enterprise-grade global load balancing with complete infrastructure control, eliminating vendor lock-in and third-party dependencies for organizations requiring autonomy.

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OpenGSLB

v1.1.9 Stable Release - Production-ready DNS-first global load balancing.

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Overview

OpenGSLB is an open-source, self-hosted Global Server Load Balancing (GSLB) system designed for intelligent traffic distribution across multiple data centers and cloud regions. Built for organizations that require complete control over their infrastructure, OpenGSLB provides enterprise-grade global load balancing without vendor lock-in or dependency on third-party services.

Licensing

OpenGSLB is dual-licensed:

AGPLv3 – Free forever for open-source projects, internal use, and anyone willing to share modifications
Commercial License – For proprietary products, appliances, SaaS, or if you prefer not to comply with AGPL obligations → licensing@opengslb.org

See LICENSE for full terms.

Features

DNS Server

A and AAAA Records: Full IPv4 and IPv6 support with automatic address family filtering
UDP and TCP: Handles both transport protocols
Configurable TTL: Per-domain TTL settings with global default fallback
Authoritative Responses: Returns proper NXDOMAIN, SERVFAIL, and NOERROR responses
DNSSEC: Automatic key management with zone signing and DS record generation

Routing Algorithms

Round-Robin: Even distribution across healthy servers with per-domain rotation
Weighted: Proportional traffic distribution based on server capacity (weight 0-1000)
Failover (Active/Standby): Predictable primary → secondary → tertiary failover with automatic return-to-primary
Geolocation-Based: Route clients to nearest region using MaxMind GeoIP2 with custom CIDR overrides
Latency-Based: Dynamically route to lowest-latency backends with EMA smoothing to prevent flapping
Learned Latency: Route based on real client-to-backend TCP RTT data collected by agents (ADR-017)
EDNS Client Subnet (ECS): Extract client location from recursive resolvers for accurate geo-routing

Health Checking

HTTP/HTTPS: Configurable endpoint path, expected status codes, and TLS support
TCP: Connection-based health checks for non-HTTP services (databases, custom protocols)
Configurable Thresholds: Separate failure and success thresholds to prevent flapping
Per-Region Configuration: Different health check settings for different server tiers
Agent-Based Monitoring: Distributed agents report health from edge locations with gossip-based sync
External Validation: Overwatch nodes independently verify agent health claims

Operations

Hot Reload: Update configuration without restart via SIGHUP signal
Structured Logging: JSON or text format with configurable log levels
Prometheus Metrics: DNS queries, health check results, routing decisions, and more
Health Status API: JSON endpoint for current server health status
Server Management API: CRUD operations for dynamic server management
CLI Management Tool: Full-featured CLI for status, overrides, and management

Deployment

Single Binary: No runtime dependencies
Docker Support: Official container images on GitHub Container Registry
Minimal Resources: Lightweight footprint suitable for edge deployment

Quick Start

From Source

# Clone and build
git clone https://github.com/loganrossus/OpenGSLB.git
cd OpenGSLB
go build -o opengslb ./cmd/opengslb

# Run with example config
./opengslb --config config/example.yaml

Docker

# Pull the latest image
docker pull ghcr.io/loganrossus/opengslb:latest

# Run with your configuration
docker run -d \
  -p 53:53/udp \
  -p 53:53/tcp \
  -p 9090:9090 \
  -v $(pwd)/config.yaml:/etc/opengslb/config.yaml \
  ghcr.io/loganrossus/opengslb:latest

Test It

# Query for IPv4
dig @localhost -p 53 app.example.com A +short

# Query for IPv6
dig @localhost -p 53 app.example.com AAAA +short

# Check metrics
curl http://localhost:9090/metrics

Configuration Example

dns:
  listen_address: ":53"
  default_ttl: 60

logging:
  level: info
  format: json

metrics:
  enabled: true
  address: ":9090"

regions:
  - name: us-east
    servers:
      - address: "10.0.1.10"
        port: 80
        weight: 100
        service: "app.example.com"  # Required in v1.1.0
      - address: "10.0.1.11"
        port: 80
        weight: 100
        service: "app.example.com"
      - address: "2001:db8::1"    # IPv6 support
        port: 80
        weight: 100
        service: "app.example.com"
    health_check:
      type: http
      interval: 30s
      timeout: 5s
      path: /health
      failure_threshold: 3
      success_threshold: 2

  - name: us-west
    servers:
      - address: "10.0.2.10"
        port: 80
        weight: 100
        service: "app.example.com"
    health_check:
      type: http
      interval: 30s
      timeout: 5s
      path: /health

  - name: database
    servers:
      - address: "10.0.3.10"
        port: 5432
        service: "db.example.com"
    health_check:
      type: tcp              # TCP health check for non-HTTP
      interval: 15s
      timeout: 3s

domains:
  - name: app.example.com
    routing_algorithm: weighted
    regions: [us-east, us-west]
    ttl: 30

  - name: api.example.com
    routing_algorithm: failover    # Active/standby
    regions: [us-east, us-west]
    ttl: 15

  - name: db.example.com
    routing_algorithm: round-robin
    regions: [database]
    ttl: 60

Documentation

Full documentation is available at docs.opengslb.org

Configuration Reference - Complete configuration options
Interactive Demos - Hands-on tutorials
Docker Deployment - Container deployment guide
API Reference - REST API documentation
Troubleshooting - Common issues and solutions

Roadmap

v1.1.9 Stable (Current)

✅ DNS server with A and AAAA record support
✅ Round-robin, weighted, and failover routing
✅ Geolocation-based routing (GeoIP + custom CIDR mappings)
✅ Latency-based routing (EMA smoothing)
✅ Learned latency routing (passive TCP RTT from agents)
✅ EDNS Client Subnet (ECS) support
✅ HTTP and TCP health checks
✅ Predictive health monitoring (CPU, memory, error rate)
✅ Agent-Overwatch distributed architecture
✅ DNSSEC support with automatic key management
✅ Server management CRUD API
✅ Multi-file configuration with includes
✅ Prometheus metrics and structured logging
✅ CLI management tool
✅ Docker deployment

Planned

🔲 Web UI dashboard (Overlord)
🔲 Kubernetes operator
🔲 DNS-over-HTTPS/TLS

Target Use Cases

Private Cloud Deployments: Multi-region infrastructure with full control
Hybrid Cloud: Intelligent routing between on-premises and cloud
Regulated Industries: Data sovereignty requirements (finance, healthcare, government)
High-Security Environments: No external dependencies or data sharing
Cost-Conscious Enterprises: Enterprise features without SaaS pricing