Description:

There are use cases where it is desirable for an HTTP proxy to return a configured HTTP response without proxying to an upstream server.

Some examples:

• If path == /some_health_check_endpoint, return a 200.
• If path == /some_invalid_url_that_clients_are_requesting_nonstop, return a 404 directly to shield the upstream from overload.

Proposed configuration model:

• Add a new action type, DirectResponseAction, that can be used in place of RouteAction and RedirectAction.
• Let the DirectResponseAction config specify the HTTP response status, an optional reason string, an optional content-type, and an optional response body.