Re: Distinguishing 0-byte request body in HTTP/2

["Roy T. Fielding" <[e-mail]>]

On Sep 15, 2016, at 3:15 PM, Roy T. Fielding <[e-mail]> wrote:
> 
>> On Sep 15, 2016, at 3:06 PM, Willy Tarreau <[e-mail]> wrote:
>> 
>> Hi Roy,
>> 
>> On Thu, Sep 15, 2016 at 01:13:01PM -0700, Roy T. Fielding wrote:
>>>> I'd be tempted to simplify this as "if you're sending a body even an empty
>>>> one, announce its size in content-length". Methods like POST and PUT expect
>>>> a message body so that should always be done.
>>> 
>>> No.  It is never a good idea to send extra information just in case you
>>> might encounter a broken server.  It is better to send less information and
>>> let people fix their own broken code.  Otherwise, the Internet becomes a
>>> cesspool of poorly imagined cases that are far less likely to exist than
>>> the keel-over-waiting-for-the-extra-TCP-packets cases that always exist.
>> 
>> But if c-l:0 is supposed to be exactly equivalent to no c-l, then what's
>> the purpose of status code 411 ? My understanding no c-l means there is
>> no body while c-l: 0 means the body is empty, both of which are totally
>> equivalent from a framing perspective, but not necessarily from a
>> semantics perspective.
>> 
>> Regards,
>> Willy
> 
> CL is present only for message framing and can be removed at any hop.
> CL:0 versus no CL has no semantic distinction whatsoever, so any recipient
> that chooses to interpret it as a distinction is inherently broken.

And the purpose of 411 is to say that Transfer-Encoding chunked isn't useful
because the resource requires a fixed length before it can be invoked (CGI).
[Actually, I think most servers attempt to read at least one buffer full
of body as chunked, to see if it happens to be a short body, and will internally
translate that to a fixed CL before continuing; otherwise, sending 411.]

....Roy