added docs for mod_cml

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.3.x@422 152afb58-edef-0310-8abb-c4023f1b3aa9

doc/Makefile.am

@@ -29,7 +29,8 @@ access.txt \
 traffic-shaping.txt \
 setenv.txt \
 status.txt \
-scgi.txt
+scgi.txt \
+cml.txt
 
 HTMLDOCS=accesslog.html \
 	 authentication.html \
@@ -59,7 +60,8 @@ HTMLDOCS=accesslog.html \
 	 traffic-shaping.html \
 	 setenv.html \
 	 status.html \
-	 scgi.html
+	 scgi.html \
+	 cml.html
 
 EXTRA_DIST=lighttpd.conf lighttpd.user \
 	rc.lighttpd rc.lighttpd.redhat sysconfig.lighttpd \

doc/cml.txt

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