Re: mp2] [mod_proxy] [filter] mod_proxy is not playing with my request filter.

James Lee wrote:
> Hi mod_perl community, this is my first post so be gentle with me.
> 
> I'm trying to create something which translates a GET request into a POST
> (creating the body dynamically) and then hand off the POST to another
> server.
> 
> I have created a mod_perl connection filter to change the GET to a POST in
> the request line. It also adds Content-Length and Content-Type headers and
> this works fine.
> 
> I then have a request filter which creates the POST body. This works when
> the request is handled by a PerlResponseHandler but I'm trying to offload
> the request to mod_proxy as the responses can be quite large but I just
> can't get it to play ball. I see the request filter being called but the
> POST body never arrives at the target server. I suspect this is a timing
> issue, ie: mod_proxy kicking in before my request filter but I'm not
> certain.

Exactly. By the time your response handler is invoked, the time for mod_proxy is long past.

One approach would be : have your PerlResponseHandler send the request directly to the 
back-end server, using LWP, read the response, and return this response as the response 
for your response handler.  In other words, do yourself what mod_proxy would do.

> 
> Can anybody shed some light on this or correct my approach. I was going to
> add the POST body in the connection filter but it seemed cleaner/easier to
> do it in a request filter.

In the mod_perl documentation, there is somewhere a schema of the different Apache phases, 
and when the different handlers get invoked.  I beliebe mod_proxygets invoked somewhere 
around the Fixup phase, so if you want to beat it, you have to be earlier than that.

> 
> I've looked on the mailing list and found a few things that touch on this (
> http://tech.groups.yahoo.com/group/modperl/message/54541) but nothing that's
> close enough to help.
> 
> Config below ... I've not included perl code as this message is quite long
> anyway. Please let me know if it would be helpful.
> Thanks in advance, James.
> 
> 
> ***
> httpd.conf extract:
> 
> 
> PerlInputFilterHandler Sample::RequestTweaker::change_get_to_post
> 
> <Location /reports>
>    PerlInputFilterHandler Sample::RequestTweaker::inject_post_data
>    ProxyPass http://appserver/reports-engine
> </Location>
>