Vaibhav Singh
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3 min read
Hermes Load Balancer

Hermes is a simple yet powerful HTTP load balancer and reverse proxy written from scratch in Go. It’s designed to optimize your network’s load distribution, ensuring smooth and reliable service delivery.

Key Features

  • HTTP load balancing and reverse proxy functionality
  • Multiple load distribution strategies
  • Active and passive health checks for backend services
  • Easy configuration via YAML file or command-line arguments
  • Docker support for simple deployment

Load Distribution Strategies

Hermes supports multiple strategies to cater to different needs:

  • Round Robin: A fair and equal distribution method, perfect for when all backend services have similar processing capabilities.
  • Weighted Round Robin: Tailor the load distribution based on the processing power of each backend, assigning more weight to stronger servers.
  • Least Connections: Smartly routes traffic to the servers with the fewest active connections, minimizing response times and maximizing efficiency.

Health Checks

Hermes ensures high availability through two types of health checks:

  • Active Checks: During request processing, if a selected backend is unresponsive, it’s immediately marked as down.
  • Passive Checks: Regular pings are sent to backends at fixed intervals to monitor their status.

Configuration

Hermes can be configured using a YAML file:

port: 80 # Port on which the load balancer will be running
healthCheckInSec: 20 # Interval for passive health checks in seconds
strategy: "least-connections" # Load balancing strategy
services: # Backend services configuration
  - name: srv1
    url: http://localhost:9001
    weight: 30
  - name: srv2
    url: http://localhost:9002
    weight: 1
  - name: srv3
    url: http://localhost:9003
    weight: 1

Running Hermes

Getting started with Hermes is straightforward:

# Using a configuration file
./hermes

# Using command-line arguments
./hermes --help

# Running with Docker Compose
docker compose up

Hermes was built to balance simplicity with power - offering robust load distribution capabilities while remaining easy to configure and deploy.