Hi,
I've been playing with the idea of adding support for the proxy module
to add stickysession cookies on behalf of the backend servers. I have
one case on my hands right now where this would be needed, and I can
think of this being of use for others too.
The way this would work is that if the proxy would see a response from a
backend to which no LB cookie was received either from the client or the
backend, a new cookie would be injected to the response. If the cookie
already exists, nothing would be done. The cookie when added would be
based on the balancer and member-name of the current worker
Before I start hacking at the code, I'd like to confirm a few things.
To start with, am I correct in assuming that others might find use for
this feature? Should I do this, what are my chances of seeing the
feature added to a future 2.2.x release?
By the way, is it just me, or is the current documentation on how the
stickysession feature works quite a bit confusing? From the docs I at
least understand it so that it would be possible to use any generic
session-id based cookie (whether it's PHPSESSION, JSESSIONID or
something else). However, both trying this in practice and looking
through the code gives a rather different view - the format of the
stickysession cookie appears to be very strict, having to match the
balancer-name and the route defined for the BalancerMember.
Regardless, back to the subject. I've been going through the proxy code,
and while it's by no means a simple module, adding this functionality
doesn't look too difficult. My current plan to attack this would be roughly:
- Add a "setsticky=Off/On" parameter to ProxyPass / ProxySet
- In ap_proxy_http_process_response, add the necessary code to check if
the cookie exists, and if not, add it. This could likely happen
somewhere near ap_proxy_read_headers. Moving get_cookie_param from
mod_proxy_balancer.c to proxy_util.c would allow to reuse it here.
Any thoughts and/or comments?
Cheers,
Jani
