I was wondering if there is a way in Nginx to force a client to close the connection (or modify the keepalive parameters) when a proxied server returns a particular error response. To elaborate a bit, if I have Nginx as a proxy in front of a backend server, can Nginx be made to change its keep alive behavior based on the error response of the back end server? For example, if I have keepalive_requests as, say 30, in my Nginx config but if the proxied server returns some 4xx or 5xx error, I'd like to send a connection close to the client or perhaps make keepalive_requests as 0 for that connection, forcing the client to open up a new connection.

One approach I tried was to intercept the error (proxy_intercept_errors on) and used the error page directive to refer to a location wherein I set the keepalive_requests as 0. This seems to make the client close the current connection but there doesn't seem to be a way to return the actual response from the backend server when using proxy_intercept_errors. It would be nice to be able to return the actual error response from the backend server than just return some static content.
Please let me know if anyone has any suggestions or ideas.
Thanks.