# nginx的502，503，504

：-}

502 Bad Gateway
The server was acting as a gateway or proxy and received an invalid response from the upstream server.
503 Service Unavailable
The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.
504 Gateway Time-out
The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.