最近在測試CDN服務質量問題，測試過程中返回了一些不同的狀態碼，當然有一些常用的，也有一些不常用的。最奇葩的是在使用curl命令的時候出現000狀態碼，問了很多同事，對這個000的反應跟新事物是的。

一、生產環境常見的HTTP CODE

生產環境常見的HTTP狀態碼列表（List of HTTP status codes）為：

2XX成功： 200 - OK，服務器成功返回網頁 　　- Standard response for successful HTTP requests.

3XX重定向： 301 - Moved Permanently（永久跳轉），請求的網頁已永久跳轉到新位置。 　　- This and all future requests should be directed to the given. 302 - Moved Temporarily（永久跳轉），請求的網頁已臨時跳轉到新位置。

4XX客戶端錯誤： 403 - Forbidden（禁止訪問）,服務器拒絕請求 　　- 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,服務器找不到請求的頁面。 　　- The requested resource could not be found but may be available again in the future.

5XX服務器錯誤： 500 - Internal Server Error（內部服務器錯誤） 　　- internal error in haproxy => HTTP 500 　　- A generic error message, given when no more specific message is suitable. 502 - Bad Gateway（壞的網關）,一般是網關服務器請求後端服務時，後端服務沒有按照http協議正確返回結果。 　　- 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（服務當前不可用）,可能因為超載或停機維護。 　　- 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（網關超時）,一般是網關服務器請求後端服務時，後端服務沒有在特定的時間內完成服務。 　　- 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.

二、curl奇怪的返回值000。

經過測試發現在curl的時候出現000的情況有如下幾種：

1.Failed DNS resolution (6)

$ curl -w "%{http_code}\n" http://example.invalid/ ; echo "Exit code: $?" 000 curl: (6) Could not resolve host: example.invalid Exit code: 6

2.Connection refused (7)

$ curl -w "%{http_code}\n" http://localhost:81/ ; echo "Exit code: $?" 000 curl: (7) Failed to connect to localhost port 81: Connection refused Exit code: 7

Connection timed out (28)

$ curl -w "%{http_code}\n" -m 5 http://10.255.255.1/ ; echo "Exit code: $?" 000 curl: (28) Connection timed out after 5001 milliseconds Exit code: 28

Server actually returns 000 for some reason (0)

開啟一個監聽端口：

nc -l -p 65535 & <<EOF

> HTTP/1.1 000 Fake Status Code

> Content-Length: 0

> Connection: close

>

>EOF

客戶端請求：

$ curl -w "%{http_code}\n" http://localhost:65535/ ; echo "Exit code: $?" 000 Exit code: 0

*註釋：一般情況下遇到000，默認考慮為200，正常。

在測試過程中打印了000時的錯誤信息，錯誤為：Connection timed out。使用curl時，參數：-sS ,然後將curl的錯誤 2>> /tmp/err.log。

常用HTTP狀態碼和CURL 000問題