43. Proxy Server Configuration
When using a proxy server it is important to ensure that you have configured your application properly. For example, many applications will have a load balancer that responds to request for https://example.com/ by forwarding the request to an application server at http://192.168.1:8080 Without proper configuration, the application server will not know that the load balancer exists and treat the request as though http://192.168.1:8080 was requested by the client.
To fix this you can use RFC 7239 to specify that a load balancer is being used. To make the application aware of this, you need to either configure your application server aware of the X-Forwarded headers. For example Tomcat uses the RemoteIpValve and Jetty uses ForwardedRequestCustomizer. Alternatively, Spring 4.3+ users can leverage ForwardedHeaderFilter.