HTTP协议必会状态码含义

200

 - OK，服务器成功返回网页 
- Standard response for successful HTTP requests.

301

 - Moved Permanently（永久跳转），请求的网页已永久跳转到新位置。
 - This and all future requests should be directed to the given.

403

- Forbidden（禁止访问）,服务器拒绝请求
- forbidden request (matches a deny filter) => HTTP 403
- The request was a legal request, but the server is refusing to respond to it.

404

 - Not Found,服务器找不到请求的页面。
 - The requested resource could not be found but may be available again in the future.

500

 - Internal Server Error（内部服务器错误）
 - internal error in haproxy => HTTP 500
 - A generic error message, given when no more specific message is suitable.

502

 - Bad Gateway（坏的网关）,一般是网关服务器请求后端服务时，后端服务没有按照http协议正确返回结果。
 - the server returned an invalid or incomplete response => HTTP 502
 - The server was acting as a gateway or proxy and received an invalid response from the upstream server.

503

 - Service Unavailable（服务当前不可用）,可能因为超载或停机维护。
 - no server was available to handle the request => HTTP 503
 - The server is currently unavailable (because it is overloaded or down for maintenance).

504

 - Gateway Timeout（网关超时）,一般是网关服务器请求后端服务时，后端服务没有在特定的时间内完成服务。
 - the server failed to reply in time => HTTP 504
 - The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.