Generic semantics for the 400 status code

[Mark Nottingham <[e-mail]>]

When people have error states that don't cleanly fit into an existing status code, they're often encouraged to use 400 or 500, depending on whether the client or server were at fault, as they're the most "generic" status codes.

500's definition fits this:

> 8.5.1.  500 Internal Server Error
> 
>    The server encountered an unexpected condition which prevented it
>    from fulfilling the request.

However, 400 is much more specific:

> 8.4.1.  400 Bad Request
> 
>    The request could not be understood by the server due to malformed
>    syntax.  The client SHOULD NOT repeat the request without
>    modifications.

I think the 400 definition needs to be broadened, so that people don't invent their own status codes, or misuse existing ones.

E.g.,

"""
The server can or will not process the request, due to a client error (e.g., malformed syntax).
"""

Additionally, I think we should move the caution against retrying the request to the general 4xx section (8.4)*.

Background:
  http://docs.openstack.org/cactus/openstack-compute/developer/openstack-compute-api-1.1/content/Synchronous_Faults-d1e1729.html#comment-213643851

Thoughts?

Cheers,


* Why is the "If the client is sending data..." section in p2 8.4? Seems like this belongs in p1...


--
Mark Nottingham   http://www.mnot.net/