In another article I wrote about my ongoing attempt to move my server’s WordPress’s security plugin’s firewall functionality out of PHP and into the embedded lua environment in Nginx. While I’m certainly not nearly as the scale where the C10K problem is a real issue for me, I still do my best to insure that I’m doing things as efficiently as possible.
In my last post, I was looking at the performance degradation between doing no firewalling at all (just building the page in WordPress and serving it), and using the embedded Lua environment to do basic application firewalling tests.
In that article, I saw approximately 425 microsecond latency impact form the Lua processing compared to just building the page. Of course, that was still on the order of 2 orders of magnitude faster than doing the same work in PHP.
Part of the larger part of the actual processing that is being done, is looking for various strings in the myriad of data that’s pushed along as part of the various requests. Things like, know bad user agents, key bits used in SQL injection attacks, and various things like that.
Lua and Nginx both offer some options for searching strings. On the Lua side, there’s the built in string.find() (Lua5.1 docs) and associated functions. On the Nginx-Lua side of things there’s ngx.re.find() (lua-nginx-module docs) which allows calls into Nginx’s regex engine.
I’ve done a significant amount of digging trying to find performance informational about both of these methods, and I haven’t been able to find any. So I sat down and did my own testing.