Health checks can be a very useful tool for load balanced web applications.

Enabling Health Checks
To enable health checks, you'll need a Server with the Load Balancer role on it. Then, add the health check URI to your application(s).

How Health Checks Work
When enabled, a request will be sent to each web server on an interval to check their status. SSL will be stripped at the load balancer so a health check request will be sent to your web servers over HTTP. The web server is also running Caddy and will proxy the request to your application to the specified URI.

Testing Health Checks Manually
You can SSH into the load balancer server and use curl to test a health check endpoint on a web server.

curl http://10.0.0.2/up -H "Host: domain.com" -H "X-Forwarded-Proto: https"

You'll need to change the IP address in this command to the private IP address of the web server. You'll also need to change the Host header to match one of the domains of the application so it can be routed to the correct application on the web server.

The X-Forwarded-Proto header is used to tell the web server that SSL has already been handled. This your application that it doesn't need to redirect to SSL for this request. Without this header, you may get infinite loops.