W3C home > Mailing lists > Public > ietf-http-wg-old@w3.org > May to August 1995

Re: Worries about content-length

From: Patrick R. Michaud <pmichaud@tamucc.edu>
Date: Tue, 9 May 1995 10:54:17 -0500
Message-Id: <199505091554.KAA06804@sunrise.tamucc.edu>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
>> But if you have the files already cached and precomputed, you might
>> as well just use Content-Length and make everyone's life easier.
>> The problem comes for non-cachable results (such as the output of
>> a CGI script subprocess), when the response has to be generated "live."
>
>But this is all really a moot point: we should be concentrating on
>http-ng so that the existing practice, warts and all, can disappear
>as soon as possible.

All the discussion I've seen thus far is about modifying _servers_
to properly mark the end of the data, but my feeling is that marking
the end of data is really the responsibility of the CGI script, not
the server.  

CGI scripts already have to generate portions of the header anyway
(e.g., "Content-Type: blah/blah" headers), so why not have a CGI
script generate a "Content-Terminator:" header while it's at it and
append the terminator itself?  Since a CGI script presumably "knows
something" about the content it's sending, any termination string
it generates is at least as good as, and probably better than, anything
the server could decide to generate.

Many CGI scripts already generate "Content-Length:" headers if they can;
it thus seems logical that marking the boundaries of the content is
really a responsibility of the CGI script and not the server.  
I can see some advantages of having a server generate a termination
header on behalf of a CGI script, but I get a bad feeling about having
servers muck around with headers (and now terminators) for content data they
know little or nothing about.  I strongly oppose the idea of messing
around with the content data itself (e.g., quoting marker characters)
except as part of a Content-Transfer-Encoding scheme.

Of course, the existence of NPH-Scripts (No Parse Header) means that a CGI
script can prevent a server from generating termination strings, at
the (minimal) expense of generating the entire HTTP response.  

Overall, I think the idea of adding a "Content-Terminator:" header 
and terminator strings to HTTP is a reasonable idea, and the idea of
designating an escape-code (not as part of a Content-Transfer-Encoding)
is a pretty bad one.  Generating content-terminator strings on behalf of a
CGI script should be a server implementation decision, and I believe 
that CGI scripts really ought to handle their own termination 
(via either "Content-Length:" or "Content-Terminator:") anyway.

Pm

--------------
Dr. Patrick R. Michaud, Assistant Professor
Department of Computing and Mathematical Sciences
Texas A&M University-Corpus Christi
6300 Ocean Drive, Corpus Christi TX 78412
email: pmichaud@tamucc.edu   voice: 512-994-2751   fax: 512-994-2715
Received on Tuesday, 9 May 1995 08:57:10 EDT

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