With a modern pcre library version and nginx, instead of<p><pre><code> location ~ ^/([a-zA-Z0-9_]+)/ {
set $username $1;
</code></pre>
you can use named captures<p><pre><code> location ~ ^/(?<username>[a-zA-Z0-9_]+)/ {</code></pre>
This is a fantastic explanation.
We have started to do something similar but your LUA rewrites is a lot more effective. I wasn't even aware that you could do something like that.
I've done very similar things with Varnish reverse caching proxy. And as a bonus, Varnish is crazy fast if your pages or assets are cacheable.<p>Its scripting language is very simple (not quite as nice as Lua, IMHO), but it supports multiple backends and rewriting arbitrary headers: <a href="https://www.varnish-cache.org/trac/wiki/VCLExamples" rel="nofollow">https://www.varnish-cache.org/trac/wiki/VCLExamples</a>
We've done this before, but by adding an additional load-balancer that forwards requests to a different port (e.g. 81 instead of 80) depending on the subdomain that was accessed. The request is processed by nginx, which has separate server blocks and associated upstreams for processing requests that come in over the configured ports. The only application logic that was necessary to accommodate the changes was a check to determine if the user should be part of the beta, and redirect them to the appropriate subodmain if necessary.<p>While it's not as clean as having the check done in nginx itself via Lua script + Redis, it's relatively low friction. That said, the Lua script embedded in the nginx config is very slick, and I had been contemplating writing something similar using the nginx memcache module. Nice work.
Good write up for a sensible solution to a problem which should effect lots of sites.<p>Personally, I would probably take the approach of settings a cookie per user. This would be very suitable when beta testing is enabled/decided by users, rather than a subset being chosen A/B style based on a value in the database. This would have the advantage that nginx would not have to make any database requests; just check a cookie on the request, likely speeding up the speed at which nginx handles requests. However, it would require some changes to the application (versus [small] changes to the database which the slug approach) to set the cookie etc.<p>I wonder how easy this is to do in apache.
Couldn't you use a cookie and map, rather than URLs? Sounds like users could end up on different rails back ends unintentionally based on what URL they use, with your method...<p><a href="http://serverfault.com/questions/268633/controlling-nginx-proxy-target-using-a-cookie" rel="nofollow">http://serverfault.com/questions/268633/controlling-nginx-pr...</a>
rather than: if (-f $request_filename)... you should use try_files<p><a href="http://wiki.nginx.org/IfIsEvil" rel="nofollow">http://wiki.nginx.org/IfIsEvil</a><p><a href="http://wiki.nginx.org/Pitfalls#Using_If" rel="nofollow">http://wiki.nginx.org/Pitfalls#Using_If</a>