[Mongrel] Transfer-Encoding: Chunked

Zed A. Shaw zedshaw at zedshaw.com
Sun Feb 17 21:18:15 EST 2008

On Fri, 15 Feb 2008 14:35:04 -0600
Zachary Roetemeyer <zprime at gmail.com> wrote:

> I'm working with someone who is having issues with a Transfer- 
> Encoding: Chunked upload. With out a content-length set in the  
> request, everything is treating the content length as 0 and the file  
> is more or less getting sent to the bit bucket.  Does anyone have any  
> experience with this kind of issue?  We started proxying with  
> nginx(returned a HTTP Error 411), then we tried to directly expose a  
> mongrel and ended up getting strange results, and errors in the  
> mongrel logs.  The client is uploading with a mobile phone using J2ME.

Uh, you aren't allowed to set a Content-Length AND use CE in the same
request.  That would let the two contradict so it's an RFC violation.
Actually, WebLogic makes this mistake and we had to school them about
it until they told us to turn it off.  (WebLogic is such a piece of

My RFC knowledge on CE is rusty since I banished that shitty part of
HTTP from my mind when I implemented it in RFuzz, but my thoughts are:

1) CE wasn't designed for clients to upload, since no browser does it.
2) It's originally for a server to send periodic parts of a request
without having to know it's total final size.
3) Anyone doing a CE as a client is seriously screwing with the RFC and
really exercising the corners of it for no apparent reason since CE
isn't needed by a client (the client knows the size, or better).
4) This puts a burden on the server to process the CE as it comes
over, which has the same problems as mime boundaries but with a more
horribly designed part of the RFC.
5) My recommendation is that you just don't do this.  The value add for
a client (or even modern servers really) is quite minimal.

Now, how you go about implementing it:

A) Read up on how to write a Mongrel handler.
B) Register it at the front of your web app or create a separate server
that runs just mongrel (probably your best if you want any kind of
C) Your handler would detect the CE via the normal headers and such,
and then process the final request body as it comes in for each chunk.
D) This might involve subclassing the Http processing parts that handle
the body and doing a bit of other hacking, and it's seriously fucking
dumb because after that you've gotta process mime boundaries and other
stuff, which will punish your server heavily.


Zed A. Shaw
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