added docs for mod_cml
git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.3.x@422 152afb58-edef-0310-8abb-c4023f1b3aa9svn/tags/lighttpd-1.3.15
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81368ccd4e
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ab76910963
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@ -29,7 +29,8 @@ access.txt \
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traffic-shaping.txt \
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setenv.txt \
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status.txt \
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scgi.txt
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scgi.txt \
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cml.txt
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HTMLDOCS=accesslog.html \
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authentication.html \
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@ -59,7 +60,8 @@ HTMLDOCS=accesslog.html \
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traffic-shaping.html \
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setenv.html \
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status.html \
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scgi.html
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scgi.html \
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cml.html
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EXTRA_DIST=lighttpd.conf lighttpd.user \
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rc.lighttpd rc.lighttpd.redhat sysconfig.lighttpd \
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@ -0,0 +1,156 @@
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=========================
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CML (Cache Meta Language)
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=========================
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---------------
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Module: mod_cml
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---------------
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:Author: Jan Kneschke
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:Date: $Date: 2004/11/03 22:26:05 $
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:Revision: $Revision: 1.2 $
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:abstract:
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CML is a Meta language to describe the dependencies of a page at one side and building a page from its fragments on the other side
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.. meta::
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:keywords: lighttpd, cml
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.. contents:: Table of Contents
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Description
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===========
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CML (Cache Meta Language) wants to solves several problems:
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* dynamic content needs caching to perform
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* checking if the content is dirty inside of the application is usually more expensive than sending out the cached data
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* a dynamic page is usually fragmented and the fragments have different livetimes
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* the different fragements can be cached independently
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Cache Decision
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--------------
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A simple example should show how to a content caching the very simple way in PHP.
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jan.kneschke.de has a very simple design:
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* the layout is taken from a template in templates/jk.tmpl
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* the menu is generated from a menu.csv file
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* the content is coming from files on the local directory named content-1, content-2 and so on
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The page content is static as long non of the those tree items changes. A change in the layout
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is affecting all pages, a change of menu.csv too, a change of content-x file only affects the
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cached page itself.
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If we model this in PHP we get: ::
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<?php
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## ... fetch all content-* files into $content
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$cachefile = "/cache/dir/to/cached-content";
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function is_cachable($content, $cachefile) {
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if (!file_exists($cachefile)) {
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return 0;
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} else {
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$cachemtime = filemtime($cachefile);
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}
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foreach($content as $k => $v) {
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if (isset($v["file"]) &&
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filemtime($v["file"]) > $cachemtime) {
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return 0;
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}
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}
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if (filemtime("/menu/menu.csv") > $cachemtime) {
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return 0;
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}
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if (filemtime("/templates/jk.tmpl") > $cachemtime) {
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return 0;
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}
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}
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if (is_cachable(...), $cachefile) {
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readfile($cachefile);
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exit();
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} else {
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# generate content and write it to $cachefile
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}
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?>
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Quite simple. No magic involved. If the one of the files is new than the cached
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content, the content is dirty and has to be regenerated.
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Now let take a look at the numbers:
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* 150 req/s for a Cache-Hit
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* 100 req/s for a Cache-Miss
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As you can see the increase is not as good as it could be. The main reason as the overhead
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of the PHP interpreter to start up (a byte-code cache has been used here).
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Moving these decisions out of the PHP script into a server module will remove the need
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to start PHP for a cache-hit.
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To transform this example into a CML you need 'index.cml' in the list of indexfiles
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and the following index.cml file: ::
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output.content-type text/html
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output.include _cache.html
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trigger.handler index.php
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trigger.if file.mtime("../lib/php/menu.csv") > file.mtime("_cache.html")
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trigger.if file.mtime("templates/jk.tmpl") > file.mtime("_cache.html")
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trigger.if file.mtime("content.html") > file.mtime("_cache.html")
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Numbers again:
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* 4900 req/s for Cache-Hit
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* 100 req/s for Cache-Miss
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Content Assembling
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------------------
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Sometimes the different fragment are already generated externally. You have to cat them together: ::
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<?php
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readfile("head.html");
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readfile("menu.html");
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readfile("spacer.html");
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readfile("db-content.html");
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readfile("spacer2.html");
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readfile("news.html");
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readfile("footer.html");
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?>
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We we can do the same several times faster directly in the webserver.
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Don't forget: Webserver are built to send out static content, that is what they can do best.
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The index.cml for this looks like: ::
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output.content-type text/html
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output.include head.html
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output.include menu.html
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output.include spacer.html
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output.include db-content.html
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output.include spacer2.html
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output.include news.html
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output.include footer.html
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Now we get about 10000 req/s instead of 600 req/s.
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Options
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=======
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:cache.extension:
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the file extension that is bound to the cml-module
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Language
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========
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... will come later ...
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