WordPress with W3 Total Cache on Nginx with APC (Virtualmin)

Virtualmin now includes support for Nginx web server. I deploy many WordPress sites with W3 Total Cache and APC Alternative PHP Cache, so I was very interested to see how Nginx performance compares to Apache for WordPress, and whether APC and W3TC would play nice with Nginx.

I prefer to install WordPress in public_html/wordpress for ease of development, compatibility with other scripts, etc. Accordingly, the suggested configuration is for WordPress installed in a subfolder. This info also assumes you have successfully installed APC Cache on your server, and set up a clean install of Virtualmin with Nginx as the Alternative Web Server. Switching from Apache to Nginx later is difficult, as is transferring apache virtual server backups. Best to start fresh and build from scratch.

Testing the Virtualmin Nginx Modules

Virtualmin does not support Nginx and Apache together, and there is no easy migration from Apache to Nginx, so it is suggested to begin with a fresh install of Virtualmin with no existing accounts.

If you would like to experiment with Nginx, and you already have a Virtualmin Pro license, you are permitted to set up Virtualmin on a second server for testing and migration. I run the extra Virtualmin Pro system on a VPS that I use for backups, slave DNS, and testing.

The Nginx modules are also available for the free Virtualmin GPL version. To install the modules, go to Virtualmin Package Updates (wbm-virtualmin-nginx and wbm-virtualmin-nginx-ssl).

WordPress Plugins for this Setup

• W3 Total Cache — adds opcode cache, minification, browser cache and page cache capabilities to WordPress… and it works with Nginx. Works best with Alternative PHP Cache to provide opcode and database cache. Setting APC for all caches works easiest with Nginx… setting to file caching introduces URL rewrite errors… See W3TC Settings information below for instructions on how to implement File caching.
• nginx Compatibility — makes WordPress more compatible with Nginx, allows use of permalinks without /index.php/

Configuring Nginx for WordPress pretty URL Permalinks

The nginx Compatibility plugin has support for pretty URLs, but you must configure Nginx to use them. You should add or edit the following URL path locations to nginx.conf for your virtual domain… either by direct edit, or via URL Path Locations in Virtualmin > Services > Configure Nginx Website (see attached image…). This config is for WP installed in /public_html/wordpress, so you will need to omit or change /wordpress if WP is installed in a different directory.

location ^~ /files/ {
rewrite /files/(.+) /wordpress/wp-includes/ms-files.php?file=$1 last;
}
location @wordpress {
fastcgi_pass localhost:9000;
fastcgi_param SCRIPT_FILENAME $document_root/index.php;
include /etc/nginx/fastcgi_params;
fastcgi_param SCRIPT_NAME /index.php;
}
location ~ \.php$ {
try_files $uri @wordpress;
fastcgi_index index.php;
fastcgi_pass localhost:9000;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include /etc/nginx/fastcgi_params;
}
location ^~ /blogs.dir/ {
internal;
root /home/username/public_html/wordpress/wp-content;
}

Adding APC Support for a Virtual Domain

Because Virtualmin’s implementation of Nginx uses php-fastcgi, each virtual domain will load its own php.ini file, so you can add the APC directives to that file (/home/domainname/etc/php5/php.ini)

Add the following to php.ini (adjust to your requirements)

[APC]
extension = apc.so
apc.enabled = 1
apc.shm_segments = 1
apc.shm_size = 12M
apc.optimization = 0
apc.num_files_hint = 256
apc.user_entries_hint = 1024
apc.ttl = 0
apc.user_ttl = 0
apc.gc_ttl = 600
apc.cache_by_default = 0
apc.filters = "-/home/username/public_html/scripts-not-to-cache/.*,-/home/username/public_html/apc/.*"
apc.slam_defense = 0
apc.use_request_time = 1
apc.mmap_file_mask = /tmp/apc.XXXXXX
apc.file_update_protection = 2
apc.enable_cli = 0
apc.max_file_size = 2M
apc.stat = 1
apc.write_lock = 1
apc.report_autofilter = 0
apc.include_once_override = 0
apc.rfc1867 = 0
apc.rfc1867_prefix = "upload_"
apc.rfc1867_name = "APC_UPLOAD_PROGRESS"
apc.rfc1867_freq = 0
apc.localcache = 1
apc.localcache.size = 256
apc.coredump_unmap = 0
apc.stat_ctime = 0

Reloading PHP-fastcgi processes after changes to php.ini

You will need to reload the php-fastcgi processes if you change php.ini. Luckily, Virtualmin creates service scripts for each virtual domain, which you can use to reload PHP.

The service scripts are located in /etc/rc.d/init.d.
php-fcgi-domain1-com
php-fcgi-domain2-com
Script allows stop, start, restart
e.g.
service php-fcgi-domain2-com restart

The service may also be restarted via Webmin > Services > Bootup and Shutdown

Memory Considerations

PHP FCGId will launch the number of sub-processes you specify in Virtualmin > Server Configuration > Website Options, so beware of the memory overhead if you specify a large number, because each will consume the amount of memory specified in  apc.shm_size. You may need to experiment with this value, depending on your server’s memory and potential traffic.

Virtualmin explains: “When PHP scripts for this domain as run via FCGId, the number of PHP processes set in this field will be kept running at all times to serve requests. You can increase this from the default of 4 to improve PHP script latency, or decrease it to reduce memory use. Setting it to None will cause PHP processes to be launched only as needed on demand, and to be cleaned up after some period of inactivity.”

Nginx support on Virtualmin is working well, and it is reported that the lead developer, Jamie Cameron, is working on a php-fpm implementation, which should increase performance and lessen memory requirements. Let’s hope this rumor is true!

W3 Total Cache Settings

Provided you use the nginx.conf settings described above, using APC cache for all W3TC categories of cache/minify/etc. will work with no additional changes to the conf file. However, if you wish to choose Disk cache for page and/or minify cache, URL rewriting will not work properly on Virtualmin. You must include the location {…} directives in the nginx.conf created in your public_html root by W3TC, and add them after the location {…} directives described above.

You can do this either by copying the directives and pasting into /etc/nginx/nginx.conf, or (better) by using an include statement:

[...]
location ^~ /blogs.dir/ {
internal;
root /home/username/public_html/wordpress/wp-content;
}
include /home/username/public_html/nginx.conf;
[...]

However, remember you will need to restart NginX web server after making changes to the W3TC configuration, because these will over-write the local nginx.conf file.

Conclusion

Sorry, no benchmarks. See my example/test site here.

Nginx support on Virtualmin is working well, though I don’t see much improvement over Apache in terms of initial index page load, or time to first byte on the WordPress test site I created.  Cached and subsequent pages load very quickly, so it looks like there is an overall improvement. All WordPress functions seem to work well: comments, image uploads, etc. are no problem. I am interested to see if there is improvement with other scripts, especially phpbb3.