http 503 Service Unavailable

5×× Server Error

503 Service Unavailable

The server is currently unable to handle the request due to a temporary overload or scheduled maintenance, which will likely be alleviated after some delay.
The server MAY send a Retry-After header field1 to suggest an appropriate amount of time for the client to wait before retrying the request.
Note: The existence of the 503 status code does not imply that a server has to use it when becoming overloaded. Some servers might simply refuse the connection.

• 1 Retry-After RFC7231 Section 7.1.3
• Source: RFC7231 Section 6.6.4

503 Code References

Rails HTTP Status Symbol :service_unavailable
Go HTTP Status Constant http.StatusServiceUnavailable
Symfony HTTP Status Constant Response::HTTP_SERVICE_UNAVAILABLE
Python2 HTTP Status Constant httplib.SERVICE_UNAVAILABLE
Python3 HTTP Status Constant http.client.SERVICE_UNAVAILABLE
Python3.5 HTTP Status Constant http.HTTPStatus.SERVICE_UNAVAILABLE