I was searching for a way to enable caching for WordPress and I stumbled across this great article.

http://blogs.law.harvard.edu/djcp/2010/01/nginx-as-a-front-end-proxy-cache-for-wordpress/

In the example that was given, there was an Apache server working the backend while an nginx server was working as a front-end cache.  Those are too many services for me, so I wanted to use just one system.  Nginx.   Here is how I did it (much of this information was taken verbatim from the link above).

First, install the WordPress Nginx proxy cache integrator into WordPress. You can download it from here:
http://wordpress.org/plugins/nginx-proxy-cache-integrator/
Activate it after it is downloaded.

Then create this file:
/etc/nginx/conf.d/proxy-common.conf

proxy_cache_path  /var/lib/nginx/cache0  levels=1:2   keys_zone=staticfilecache:180m  max_size=250m;

proxy_temp_path /var/lib/nginx/proxy;
proxy_connect_timeout 30;
proxy_read_timeout 120;
proxy_send_timeout 120;

upstream wordpressapache {
        #The upstream apache server. You can have many of these and weight them accordingly,
        #allowing nginx to function as a caching load balancer (oh my. Awesomeness abounds.)
        server 127.0.0.1:81 weight=1 max_fails=3 fail_timeout=30s;
}

First, copy /etc/nginx/sites-enabled/default to /etc/nginx/sites-enabled/default.proxy

cp /etc/nginx/sites-enabled/default /etc/nginx/sites-enabled/default.proxy

Then, I changed this line in /etc/nginx/sites-enabled/default from

server {
	listen   *:80; ## listen for ipv4

to this

server {
	listen   *:81; ## listen for ipv4

This basically tells nginx to listen on port 81 instead of 80, which we will find out why soon enough.

Now, edit /etc/nginx/sites-enabled/default.proxy and add the following under the server section.

		
# Set the hostname
proxy_set_header Host $host;

#Set the forwarded-for header.
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

location / {
     index  index.php index.htm tracker.php;
     # If logged in, don't cache.
     if ($http_cookie ~* "comment_author_|wordpress_(?!test_cookie)|wp-postpass_" ) {
            set $do_not_cache 1;
     }
     proxy_cache_key "$scheme://$host$request_uri $do_not_cache";
     proxy_cache staticfilecache;
     proxy_pass http://wordpressapache;
}

location ~* wp\-.*\.php|wp\-admin {
     # Don't static file cache admin-looking things.
     proxy_pass http://wordpressapache;
}

location ~* \.(jpg|png|gif|jpeg|css|js|mp3|wav|swf|mov|doc|pdf|xls|ppt|docx|pptx|xlsx)$ {
     # Cache static-looking files for 120 minutes, setting a 10 day expiry time in the HTTP header,
     # whether logged in or not (may be too heavy-handed).
     proxy_cache_valid 200 120m;
     expires 864000;
     proxy_pass http://wordpressapache;
     proxy_cache staticfilecache;
}

location ~* \/[^\/]+\/(feed|\.xml)\/? {
     # Cache RSS looking feeds for 45 minutes unless logged in.
     if ($http_cookie ~* "comment_author_|wordpress_(?!test_cookie)|wp-postpass_" ) {
            set $do_not_cache 1;
     }
     proxy_cache_key "$scheme://$host$request_uri $do_not_cache";
     proxy_cache_valid 200 45m;
     proxy_cache staticfilecache;
     proxy_pass http://wordpressapache;
}

location = /50x.html {
     root   /var/www/nginx-default;
}

location ~ /\.ht {
     deny  all;
}

Now run the following to get your site back online.

service nginx reload