[Mongrel] Writing a mod_put HttpHandler

cremes.devlist at mac.com cremes.devlist at mac.com
Sun Nov 26 19:00:15 EST 2006

On Nov 26, 2006, at 4:14 PM, Ezra Zygmuntowicz wrote:

> On Nov 26, 2006, at 1:17 PM, cremes.devlist at mac.com wrote:
>> I'm looking at writing a Mongrel handler that mimics the behavior of
>> the Apache mod_put [1]. It allows for the streaming upload of very
>> large (GB) files; it also supports resumable upload.
>> Before I get too involved, I'd like to ask if my reading of the
>> mongrel source code is correct, i.e. what I want to do isn't
>> currently possible.
>> [snip[
> 	You are correct. The way mongrel upload progress works is mongrel
> itself streams to a tmpfile before it passes the request to any
> handlers. Then by the tiem your handler gets the request it has to
> parse the mime boundaries again which is inefficient. Zed is working
> on a fast C mime carver and I am going to implement a way to grab the
> tmpfile mongrel makes without reparsing it but we haven't made
> progress yet.


I don't see where Mongrel is doing any mime parsing in the  
HttpRequest class. As far as I can see, it's just dumping the  
contents of @params.http_body to a TempFile without any intermediate  

> 	So let me know if you end up workign on this or if you want to work
> with me to come up with a way to get the first tmpfile without
> reparsing.

Sure, I'd like to work with you on this. I either get this working in  
Mongrel or I bite the bullet and use Apache/mod_put (which, in my  
particular circumstances, will require me to bend all sorts of other  

What ideas have you developed for grabbing the TempFile? From a  
cursory look at the code, here's my first idea. Feel free to poke  
holes in it.

1. Modify the HttpRequest class to stop reading from  
@params.http_body into @body at Mongrel::MAX_BODY bytes. Set internal  
flag on this request to indicate the request is unfinished.
2. Add #done? to HttpRequest class to test internal flag and return  
its true/false state.
3. Modify HttpServer#process_client in the following ways:
3a. Do not allocate an HttpResponse object unless request.done?
3b. Do not finalize the response object until request.done?

This would have the effect of calling handlers with a nil 'response'  
and a potentially unfinalized 'request' which would probably break  
all current handlers. :-(

Alternately, create a second chain of handlers which register for  
'partial requests' and only call the other handler chain when the  
request and response objects are whole/finalized.

We avoid the use of TempFiles altogether with this approach and allow  
this new class of handler to be the first to hit the disk. If the  
TempFile behavior is necessary for other handler's proper operation,  
Mongrel could ship with a handler that restores this functionality as  
the default.


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