进程未运行的最佳HTTP错误代码？

Question

I am in process of building a rest server, which will be called to abort a long running process by client.

/abort/{processID}

Now if process with processID is not found, I am returning 404 Not Found

However if the process has already been completed/is not running, then what shall be correct HTTP Error code for the same?

406 Not Acceptable is relevant to Accept header (and hence I think I shall not used).

400 Bad Request appears to be too generic.

Seeking suggestions on which header will be optimum for it?

Answer 1

Short answer

Here are some reasonable options that may suit you:

• 404 Not Found
• 410 Gone
• 409 Conflict
• 403 Forbidden

The right choice relies on the semantics of process has already been completed/is not running :

• If the process no longer exists, consider 404 or 410 , depending on whether the condition is permanent or not.
• If a process can be found with a given id, but the attempt to abort this process cannot be completed due to a conflict with the current state of the process, you could go for 409 .
• If the operation is forbidden for other reasons, choose 403 .

The process no longer exists

If the process no longer exists, you could choose between 404 and 410 , depending on whether the condition is (or it is possible to determine whether the condition is) permanent or not.

See the following quotes from the RFC 7231 :

6.5.4. 404 Not Found

The 404 (Not Found) status code indicates that the origin server did not find a current representation for the target resource or is not willing to disclose that one exists. A 404 status code does not indicate whether this lack of representation is temporary or permanent; the 410 (Gone) status code is preferred over 404 if the origin server knows, presumably through some configurable means, that the condition is likely to be permanent. [...]

6.5.9. 410 Gone

The 410 (Gone) status code indicates that access to the target resource is no longer available at the origin server and that this condition is likely to be permanent. If the origin server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 (Not Found) ought to be used instead. [...]

The process exists, but the operation causes a conflict

If the process exists, 404 or 410 are not the good choices.

If the attempt to abort an existing process cannot be completed due to a conflict with the current state of the process, you should consider 409 along with a payload that describes the reason of the conflict.

See the quote:

6.5.8. 409 Conflict

The 409 (Conflict) status code indicates that the request could not be completed due to a conflict with the current state of the target resource. This code is used in situations where the user might be able to resolve the conflict and resubmit the request. The server SHOULD generate a payload that includes enough information for a user to recognize the source of the conflict. [...]

The process exists, but the operation is forbidden for some reason

One last option is 403 . This status code is frequently used for authorization problems, when the credentials are valid, but they are insufficient to authorize the request.

However 403 is much broader than that and could be used to indicate that a request is forbidden for reasons unrelated to the credentials . Just be sure you provide a payload that describes why the operation is forbidden.

See the quote:

6.5.3. 403 Forbidden

The 403 (Forbidden) status code indicates that the server understood the request but refuses to authorize it. A server that wishes to make public why the request has been forbidden can describe that reason in the response payload (if any).

If authentication credentials were provided in the request, the server considers them insufficient to grant access. The client SHOULD NOT automatically repeat the request with the same credentials. The client MAY repeat the request with new or different credentials. However, a request might be forbidden for reasons unrelated to the credentials.

An origin server that wishes to "hide" the current existence of a forbidden target resource MAY instead respond with a status code of 404 (Not Found).