Using Nginx for Hosting and Routing APIs

1. Hosting APIs with Nginx

When used to host APIs, Nginx serves as a reverse proxy that receives incoming HTTP(S) requests and forwards them to backend services (often written in Node.js, Python, Go, etc.).

Example

Let’s say you have a REST API running on localhost:3000. You can configure Nginx to expose it on https://api.example.com/ like so:

server {
    listen 80;
    server_name api.example.com;

    location / {
        proxy_pass http://localhost:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

This configuration:

• Routes all requests from api.example.com to the backend app on port 3000.
• Preserves the client IP and host info for the backend.

2. API Routing with Nginx

In microservices, you may have multiple services (e.g., /users, /orders, /payments). Nginx routes incoming requests to the correct service.

Example

server {
    listen 80;

    location /users/ {
        proxy_pass http://user-service:4000/;
    }

    location /orders/ {
        proxy_pass http://order-service:5000/;
    }

    location /payments/ {
        proxy_pass http://payment-service:6000/;
    }
}

This configuration lets you route:

• /users/... → user service
• /orders/... → order service
• /payments/... → payment service

3. Service Discovery with Nginx

Nginx itself does not do dynamic service discovery out of the box. But there are three common ways to integrate it:

A. Static Configuration

You define backend IPs or hostnames directly in the config.

upstream user_service {
    server 10.0.0.21:4000;
    server 10.0.0.22:4000;
}

B. DNS-based Service Discovery

If you’re in a dynamic environment (e.g., Docker Swarm, Kubernetes), services can be registered via DNS:

upstream user_service {
    server user-service.default.svc.cluster.local:4000;
}

C. Dynamic Reconfiguration

You can use tools to auto-update the Nginx config when services change:

• Consul Template: Watches for changes and rewrites nginx.conf.
• Lua + Nginx (via OpenResty): Allows dynamic routing logic within Nginx itself.

Bonus: Nginx as an API Gateway

If you use Nginx Plus, you get features like:

• Active health checks
• JWT validation
• Rate limiting
• Advanced load balancing
• Native service discovery

With OpenResty (Nginx + Lua), you can build custom logic. Example:

-- Lua-based routing
if uri:match("^/v2/users") then
    proxy_pass("http://new-user-service")
end

Summary Table

Role	What Nginx Does
API Hosting	Acts as reverse proxy to backend services
API Routing	Directs requests to correct microservice
API Discovery	Via DNS, templates, or Lua scripting
Load Balancing	Distributes traffic across instances
SSL Termination	Handles HTTPS so backend doesn’t have to