Upstream: honor the "down" flag for a single server. If an upstream block was defined with the only server marked as "down", e.g. upstream u { server 127.0.0.1:8080 down; } an attempt was made to contact the server despite the "down" flag. It is believed that immediate 502 response is better in such a case, and it's also consistent with what is currently done in case of multiple servers all marked as "down".