Recently I started to tackle a load problem on one of my personal sites, the issue was that of a poorly written but exceedingly MySQL heavy application and the load it would induce on the SQL server when 400-500 people were hammering the site at once. Further compounding this was Apache’s horrible ability to gracefully handle excessive requests on object heavy pages (i.e: images). This left me with a site that was almost unusable during peak hours — or worse — would crash the MySQL server and take Apache with it by frenzied F5ing from users.
I went through all the usual rituals in an effort to better the situation, from PHP APC then Eaccelerator, to mod_proxy+mod_cache, to tuning Apache timeouts/prefork settings and adjusting MySQL cache/buffer options. The extreme was setting up a MySQL replication cluster with MySQL-Proxy doing RW splitting/load balancing across the cluster and memcached, but this quickly turned into a beast to manage and memcached was eating memory at phenomenal rates.
Although I did improve things a bit, I had done so at the expense of vastly increased hardware demand and complexity. However, the site was still choking during peak hours and in a situation where switching applications and/or getting it reprogrammed is not at all an option, I had to start thinking outside the box or more to the point, outside Apache.
I have experience with lighttpd and pound reverse proxy, they are both phenomenal applications but neither directly handles caching in a graceful fashion (in pounds case not at all). This is when I took a look a nginx which to date I had never tried but heard many great things about. I fired up a new Xen guest running CentOS 5.4, 2GB RAM & 2 CPU cores….. an hour later I had nginx installed, configured and proxy-caching traffic for the site in question.
The impact was immediate and significant — the SQL server loads dropped from an average of 4-5 down to 0.5-1.0 and the web server loads were near non-existent from previously being on the brink of crashing every afternoon.
Enough with my ramblings, lets get into nginx. You can download the latest release from http://nginx.org and although I could not find a binary version of it, compiling was straight forward with no real issues.
First up we need to satisfy some requirements for the configure options we will be using, I encourage you to look at ‘./configure –help’ list of available options as there are some nice features at your disposal.
# yum install -y zlib zlib-devel openssl-devel gd gd-devel pcre pcre-devel
Once the above packages are installed we are good to go with downloading and compiling the latest version of nginx:
# wget http://nginx.org/download/nginx-0.8.36.tar.gz
# tar xvfz nginx-0.8.36.tar.gz
# cd nginx-0.8.36/
# ./configure –with-http_ssl_module –with-http_realip_module –with-http_addition_module –with-http_image_filter_module –with-http_gzip_static_module
# make && make install
This will install nginx into ‘/usr/local/nginx’, if you would like to relocate it you can use ‘–prefix=/path’ on the configure options. The path layout for nginx is very straight forward, for the purpose of this post we are assuming the defaults:
# ls /usr/local/nginx
conf fastcgi_temp html logs sbin
# cd /usr/local/nginx
# ls conf/
fastcgi.conf fastcgi.conf.default fastcgi_params fastcgi_params.default koi-utf koi-win mime.types mime.types.default nginx.conf nginx.conf.default win-utf
The layout will be very familiar to anyone that has worked with Apache and true to that, nginx breaks the configuration down into a global set of options and then the individual web site virtual host options. The ‘conf/’ folder might look a little intimidating but you only need to be concerned with the nginx.conf file which we are going to go ahead and overwrite, a copy of the defaults is already saved for you as nginx.conf.default.
My nginx configuration file is available here , be sure to rename it to nginx.conf or copy the contents listed below into ‘conf/nginx.conf’:
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