Using memcache to set variables

Johan Bergström johan at
Wed Aug 12 17:08:25 MSD 2009

On Aug 8, 2009, at 05:13 , Avleen Vig wrote:

> I started using the geo module to direct users by IP address, this
> week, and really like it!
> It got me thinking about another thing I've been wanting to do: Direct
> users to different machines based on some arbitrary data. I don't want
> to rely just on cookies, because those can be manipulated. Here's what
> I was thinking, and I'm wondering if it can be done some how in nginx?
> The sessionid is stored in a cookie. This can't be manipulated or the
> users ends up not being logged in.
> Store the sessionid in memcache, and have the value set to the name of
> a location.
> Have nginx fetch the value for 'sessionid' from memcache, and then
> redirect the user internally to that location.
> Is this even remotely possible? I think some hardware load balancers
> can do it, but I'm too poor to buy one of those :-)

We're doing something similar - through a FastCGI-app written in C -  
which looks up a host as key in memcached (cookie would work just as  
fine) and returns a backend (we have lots of different nginx backends)  
that the frontends proxies to. The key here is to use X-Accel- 
Redirect. So, in short: Yes, it's possible and delivers ~2k r/s per  
frontend for us. A FastCGI/whatever app written in php/python would  
probably work just as well, port to C when performance is needed.

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