Load balancing

A Traefik load-balancer service distributes requests for one domain across multiple upstream URLs. The upstreams can be containers on the same server or services on other servers, as long as the coolify-proxy container can reach every URL.

Prepare the upstreams

Before creating the route:

• deploy at least two healthy upstream instances
• expose each upstream on an address and port reachable from the Traefik container
• point the public domain to the server running this Traefik proxy
• decide whether Traefik should terminate HTTPS for the public domain
• remove any other resource route that uses the same hostname and path

Do not use localhost for an upstream unless the service runs inside the Traefik container. For a host service, use host.docker.internal:<port>. For a container on a shared Docker network, use its container or service name and internal port.

Add the load-balancer route

Open Servers > your server > Proxy > Dynamic Configurations, select Add, and create app-load-balancer.yaml.

http:
  middlewares:
    load-balancer-https-redirect:
      redirectScheme:
        scheme: https

  routers:
    app-load-balancer-http:
      rule: 'Host(`app.example.com`)'
      entryPoints:
        - http
      middlewares:
        - load-balancer-https-redirect
      service: app-load-balancer

    app-load-balancer-https:
      rule: 'Host(`app.example.com`)'
      entryPoints:
        - https
      service: app-load-balancer
      tls:
        certResolver: letsencrypt

  services:
    app-load-balancer:
      loadBalancer:
        healthCheck:
          path: /health
          interval: 10s
          timeout: 3s
        servers:
          - url: 'http://192.168.1.23:3000'
          - url: 'http://192.168.1.65:3000'

Verify traffic distribution

Save the dynamic configuration, then:

1. Open the public domain and confirm it responds.
2. Check Servers > your server > Proxy > Logs for connection or configuration errors.
3. Stop one upstream and confirm requests continue through a healthy upstream.
4. Restore the upstream and confirm it returns to service.

If every request returns a gateway error, test each upstream URL from the proxy network and confirm the service listens on the documented internal port.