OpenGSLB Documentation

Open-source Global Server Load Balancer with DNS-based traffic management

OpenGSLB is an enterprise-grade DNS-based load balancer that provides intelligent traffic distribution across multiple backend servers. It uses a simplified agent-overwatch architecture for reliability and ease of operation.

Key Features

  • DNS-based Load Balancing: Route traffic using DNS responses without proxying

  • Multiple Routing Algorithms: Round-robin, weighted, failover, geolocation, and latency-based routing

  • Geolocation Routing: Route traffic based on client geographic location using MaxMind GeoIP2 databases with EDNS Client Subnet (ECS) support

  • Latency-Based Routing: Route to lowest-latency servers with exponential moving average (EMA) smoothing

  • Health Checking: HTTP, HTTPS, and TCP health checks with configurable thresholds

  • Agent-Overwatch Architecture: Distributed health monitoring with centralized DNS serving

  • DNSSEC Support: Cryptographic authentication of DNS responses

  • Predictive Health: CPU, memory, and error rate monitoring for proactive failover

  • External Overrides: API for CloudWatch, Watcher, or custom tool integration

  • Multi-File Configuration: Split configuration across multiple files with glob pattern support

  • CLI Management Tool: Command-line tool for status monitoring, overrides, and configuration validation

Architecture Overview

┌─────────────────────────────────────────────────────────┐
│  DNS Clients (resolv.conf with multiple nameservers)    │
│       │           │           │                         │
│       ▼           ▼           ▼                         │
│  ┌──────────┐ ┌──────────┐ ┌──────────┐                │
│  │Overwatch1│ │Overwatch2│ │Overwatch3│                │
│  └─────┬────┘ └─────┬────┘ └─────┬────┘                │
│        │            │            │                      │
│        └────────────┼────────────┘                      │
│                     │ Gossip                            │
│            ┌────────┼────────┐                          │
│            ▼        ▼        ▼                          │
│       ┌────────┐ ┌────────┐ ┌────────┐                 │
│       │ Agent  │ │ Agent  │ │ Agent  │                 │
│       │ + App  │ │ + App  │ │ + App  │                 │
│       └────────┘ └────────┘ └────────┘                 │
└─────────────────────────────────────────────────────────┘

Getting Started

Installation

# Clone the repository
git clone https://github.com/LoganRossUS/OpenGSLB.git
cd OpenGSLB

# Build
go build -o opengslb ./cmd/opengslb

# Run
./opengslb --config config.yaml

Basic Configuration

mode: overwatch

dns:
  listen_address: "0.0.0.0:53"
  zones:
    - gslb.example.com

gossip:
  bind_address: "0.0.0.0:7946"
  encryption_key: "your-32-byte-base64-key"

validation:
  enabled: true
  check_interval: 30s

License

OpenGSLB is dual-licensed:

  1. AGPLv3 - Free for open-source and internal use

  2. Commercial License - Available for proprietary integration

See LICENSE for details.

Getting Started

Demos

Architecture

API Reference

Operations

Security

Development