What Does Your Webserver Do When a User Hits Refresh? - Shopify

This post details a specific patch to the Unicorn webserver that adds a `check_client_connection` configuration option. This option allows Unicorn to write a small amount of data to the client socket before rendering a response. If the write fails (indicating a disconnected client), the request is dropped, preventing wasted application server resources. This directly addresses the problem of HTTP 499 responses and the snowball effect during flash sales.