Path-Based Reverse Proxying with Caddy

Caddy is a great web server built with Go and can be used for a multitude of things. Here at Vizalo we use it on nearly all of our servers that power our network.

This guide explains how to set up Caddy as a reverse proxy that routes traffic to different backend services based on URL paths. This is useful when you have multiple services running on different ports and want to expose them under a single domain.

Basic Setup

Create a Caddyfile in your project directory:

example.com {
    handle /api/* {
        reverse_proxy localhost:3000
    }

    handle /admin/* {
        reverse_proxy localhost:8080
    }

    handle /* {
        reverse_proxy localhost:5000
    }
}

This configuration will:

• Send /api/* requests to a service running on port 3000
• Send /admin/* requests to a service running on port 8080
• Send all other requests to port 5000

A More Complete Example

Here's a more practical example that includes common settings you might need:

example.com {
    # API Service
    handle /api/* {
        reverse_proxy localhost:3000 {
            header_up Host {upstream_hostport}
            header_up X-Real-IP {remote_host}
            header_up X-Forwarded-For {remote_host}
        }
    }

    # Admin Dashboard
    handle /admin/* {
        reverse_proxy localhost:8080 {
            # Health checks
            health_uri /health
            health_interval 30s

            # Timeout settings
            timeout 30s
        }
    }

    # Frontend App
    handle /* {
        reverse_proxy localhost:5000 {
            # Load balancing
            lb_policy round_robin
            lb_try_duration 30s
        }

        # Enable compression
        encode gzip
    }

    # Global options
    log {
        output file /var/log/caddy/access.log
        format json
    }
}

Running Multiple Backend Services

For testing, you might run these simple backend services:

# API Service (Node.js/Express)
node api.js        # Runs on :3000

# Admin Dashboard (Go)
go run admin.go    # Runs on :8080

# Frontend (React)
npm start         # Runs on :5000

Verifying the Setup

Test your configuration:

# Test API endpoint
curl example.com/api/users

# Test admin endpoint
curl example.com/admin/dashboard

# Test frontend
curl example.com

Common Patterns

Stripping Path Prefixes

If your backend service doesn't expect the /api prefix:

handle /api/* {
    uri strip_prefix /api
    reverse_proxy localhost:3000
}

Adding Headers

Add authentication headers or API keys:

handle /api/* {
    reverse_proxy localhost:3000 {
        header_up X-API-Key {env.API_KEY}
    }
}

That's it. The beauty of Caddy is that it handles HTTPS certificates automatically and has sensible defaults for most settings. Most of the "extra" configurations shown above are only needed for specific use cases.