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From "Tom Wells" <>
Subject Re: [users@httpd] Mod_Proxy and 100-Continue
Date Tue, 30 Sep 2008 16:00:56 GMT
On Tue, Sep 30, 2008 at 11:00 AM, Nick Kew <> wrote:
> On Tue, 30 Sep 2008 09:50:00 -0400
> "Tom Wells" <> wrote:
> The "early" keyword exists to help developers simulate
> a request, for example when debugging a new module.
> Perhaps it should've remained undocumented.

Exactly - and I've used it for debugging!

Maybe I should have explained my real situation which sent me down
this road, I know this is a busy list so I didn't want to bore people
:) I've developed a mod_python module which hooks into the authen and
authz Apache handlers in order to provide a common authentication and
security module in front of a set of back-end webservers. So requests
come into the Apache machine, my handlers do some fancy cookie
checking and updating and either allow the request to continue
processing (and onto the back-end webserver via modproxy) or respond
with a redirect (to get rid of a not logged in user, or a bad cookie
or whatever). This means we have a single "logical" session and
multiple disparate webservers in the back, which is nice.

So in the "real" app I don't actually use mod_header for anything, I
just used it to demonstrate the issue I was having with mod_proxy (and
thus remove any 3rd party dependencies such as mod_python and my
custom module from the mix). In my "real" app I set the Set-Cookie
header within a mod_python structure called req.headers_out, which
marshals to the Apache r->headers_out structure. Sorry to cause any
confusion here.

> HTTP has no provision for a proxy to set an end-to-end header
> such as Set-Cookie - only how it should deal with headers set by
> the backend.  mod_headers isn't part of the protocol implementation;
> it's a convenience for users who want to change the default behaviour.

Ok I understand this - but modproxy does seem to provide this
behaviour, which is great, but differs between 2.2.4 and 2.2.9 when
dealing with 100-Continue responses.

> But it's not a bug now, nor was it before.  If you want to set
> a header with predictable behaviour, don't use "early".

Maybe it's not a bug, but it certainly is inconsistent - and certainly
something has has changed between the versions - so I wanted to
highlight this. In the meantime however we have worked around this
issue by stripping the "Expect: 100-Continue" from any inbound POSTs
before the request is processed by modproxy. This works OK as I assume
our clients don't really care about the "HTTP/1.1 100 Continue" before
sending their POST body - but we have tested this only with a C# .NET


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