fastcgi_cache + conditional purging + (optional) Domain-Mapping

Update: This article is updated for WordPress 3.5 multisite’s file-handling.

This article is a direct extension of yesterday’s article: WordPress + Nginx + fastcgi_cache with fastcgi_cache_purge module

Please read this to check if your Nginx is complied withfastcgi_cache_purge module, installing Nginx Helper plugin for your WordPress and few more important things.

WordPress-Multisite + Subdomains/Domain-Mapping + Nginx + fastcgi_cache with fastcgi_cache_purge module

Make changes to /etc/nginx/sites-available/example.com file so it looks like one below:

#move next 3 lines to /etc/nginx/nginx.conf if you want to use fastcgi_cache across many sites 
fastcgi_cache_path /var/run/nginx-cache levels=1:2 keys_zone=WORDPRESS:500m inactive=60m;
fastcgi_cache_key "$scheme$request_method$host$request_uri";
fastcgi_cache_use_stale error timeout invalid_header http_500;

server {
	#@DM - uncomment following line for domain mapping or you will need to add every mapped-domain to server_name list 
	#listen 80 default_server;
	server_name example.com *.example.com ;
	#@DM - uncomment following line for domain mapping
	#server_name_in_redirect off;

	access_log   /var/log/nginx/example.com.access.log;
	error_log    /var/log/nginx/example.com.error.log;

	root /var/www/example.com/htdocs;
	index index.php;

	#fastcgi_cache start
	set $skip_cache 0;

	# POST requests and urls with a query string should always go to PHP
	if ($request_method = POST) {
		set $skip_cache 1;
	}   
	if ($query_string != "") {
		set $skip_cache 1;
	}   

	# Don't cache uris containing the following segments
	if ($request_uri ~* "(/wp-admin/|/xmlrpc.php|/wp-(app|cron|login|register|mail).php|wp-.*.php|/feed/|index.php|wp-comments-popup.php|wp-links-opml.php|wp-locations.php|sitemap(_index)?.xml|[a-z0-9_-]+-sitemap([0-9]+)?.xml)") {
		set $skip_cache 1;
	}   

	# Don't use the cache for logged in users or recent commenters
	if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") {
		set $skip_cache 1;
	}

	location / {
		try_files $uri $uri/ /index.php?$args;
	}    

	location ~ .php$ {
		try_files $uri /index.php; 
		include fastcgi_params;
		fastcgi_pass unix:/var/run/php5-fpm.sock;

		fastcgi_cache_bypass $skip_cache;
	        fastcgi_no_cache $skip_cache;

		fastcgi_cache WORDPRESS;
		fastcgi_cache_valid  60m;
	}

	location ~ /purge(/.*) {
	    fastcgi_cache_purge WORDPRESS "$scheme$request_method$host$1";
	}	

	location ~* ^.+.(ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|rss|atom|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ {
		access_log off;	log_not_found off; expires max;
	}

	location = /robots.txt { access_log off; log_not_found off; }
	location ~ /. { deny  all; access_log off; log_not_found off; }
}

The line fastcgi_cache_use_stale is what makes caching on Nginx-side unique. This line tells nginx to use old (stale) cached version of page if PHP crashes. This is something not possible with WordPress caching plugins.

Domain Mapping

You need to uncomment few lines in above nginx-config to get domain-mapping working. Apart from above config changes, you can read this guide to setup/configure domain-mapping.

Must Read:

• Checklist For Perfect WordPress-Nginx Setup - It will help you verify if your caching will work after PHP/MySQL crash.
• Nginx Maps for Better Static File Handling in WordPress-Multisite - useful for multisite created before WordPress 3.5 released
• WordPress-Nginx tutorials