Tag Archives: wp-super-cache

WP-super-cache on lighttpd

Because my web server does not have a lot of processing power, dynamic web pages can sometimes be a bit slow. Especially if the server is busy. Serving static HTML pages is a lot better than serving PHP pages. In fact, most of the blogs on this site are just static “copies”. Using a web site downloader, such a HTTrack, I’ve made an exact copy of the web sites. This copy is served, instead of the dynamic content.

This server blog is a live blog, so I cannot make a static copy. But with the WordPress plugin WP-super-cache you can make caches of all pages. If a specific page is available in the cache, the cached paged in served. This saves a lot of executing time; no need to go to the database and get all the content. The cache has a time-out, so at regular intervals the caches are refreshed. And if a new post or comment is made, the cache is refreshed too. So users of the site won’t see any difference.

WP-super-cache supports two modes: the mod_rewrite and PHP. PHP will always work, but pages are served via PHP. The PHP script checks if a cache file exists, and serves that. This is still a lot faster than when PHP has to contact the database to build the page. But is still uses PHP. The other mode is mod_rewrite, but this is very specific to an Apache webserver. Because this site is running lighttpd, I had to search for the correct instructions. There are sites that describe a solution. However, after some debugging, I found out the solution doesn’t actually work (although it seems to work because the PHP mode is used). Also, when running WordPress as a multiblog site, images are also served using PHP. The solution below eliminates any executing of PHP when there is a static page available.

A special module, mod_magnet, in needed for lighttpd. First, install mod_magnet for lighttpd:
sudo aptitude install lighttpd-mod-magnet
Next, enable mod_magnet by runnuing:
sudo lighty-enable-mod magnet

Next, add a magnet rule to a site. In a previous post I explained how to add a site to the lighttpd configuration. To enable magnet for a site, a line needs to be added. The complete configuration then looks like this:

$HTTP["host"] =~ "server.vijge.net" {
server.document-root = "/home/www/wordpress"
var.wp_blog = 1
magnet.attract-physical-path-to = ( server.document-root + "/rewrite.lua" )
include "wpmu-rewrite.conf"

As you can see, a file called rewrite.lua is used. Create a file with this name in the WordPress installation directory. Paste the following code into the file:
[code lang=”lua”]
function serve_html(cached_page)
if (lighty.stat(cached_page)) then
lighty.env[“physical.path”] = cached_page
–print(“Serving cached page: ” .. cached_page)
return true
return false

function serve_gzip(cached_page)
if (lighty.stat(cached_page .. “.gz”)) then
lighty.header[“Content-Encoding”] = “gzip”
lighty.header[“Content-Type”] = “”
lighty.env[“physical.path”] = cached_page .. “.gz”
–print(“Serving gzipped page: ” .. cached_page .. “.gz”)
return true
return false

if (lighty.env[“uri.scheme”] == “http”) then
ext = “.html”
ext = “-https.html”

cached_page = lighty.env[“physical.doc-root”] .. “/wp-content/cache/supercache/” .. lighty.request[“Host”] .. lighty.env[“request.orig-uri”] .. “/index” .. ext
cached_page = string.gsub(cached_page, “//”, “/”)

attr = lighty.stat(cached_page)

if (attr) then
query_condition = not (lighty.env[“uri.query”] and string.find(lighty.env[“uri.query”], “.*s=.*”))
user_cookie = lighty.request[“Cookie”] or “no_cookie_here”
cookie_condition = not (string.find(user_cookie, “.*comment_author.*”) or (string.find(user_cookie, “.*wordpress.*”) and not string.find(user_cookie,”wordpress_test_cookie”)) or string.find(user_cookie, “.*wp-postpass_.*”))
if (query_condition and cookie_condition) then
accept_encoding = lighty.request[“Accept-Encoding”] or “no_acceptance”
if (string.find(accept_encoding, “gzip”)) then
if not serve_gzip(cached_page) then serve_html(cached_page) end

Finally, add the following line to the wp-config.php file in the WordPress directory:
define('WP_CACHE', true);
Now you can go to the WordPress admin pages and configure everything. The mode setting in the admin pages does not have any effect. The rewrite.lua is always used. I recommend setting the mode to PHP, because setting it to mod_write will give an error that mod_rewrite is not enabled.