brian 99/01/14 16:57:11
Added: htdocs/manual/vhosts mass.html Log: This is the document on how to use mod_rewrite to eliminate the need for virtualhost settings in the config file. Many thanks to Tony Finch <[EMAIL PROTECTED]> for contributing this! Revision Changes Path 1.1 apache-1.3/htdocs/manual/vhosts/mass.html Index: mass.html =================================================================== <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML><HEAD> <TITLE>Dynamically configured mass virtual hosting</TITLE> </HEAD> <!-- Background white, links blue (unvisited), navy (visited), red (active) --> <BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#000080" ALINK="#FF0000" > <!--#include virtual="header.html" --> <H1 ALIGN="CENTER">Dynamically configured mass virtual hosting</H1> <P>This document describes how to efficiently serve an arbitrary number of virtual hosts with Apache 1.3. Some familiarity with <A HREF="../mod/mod_rewrite.html"><CODE>mod_rewrite</CODE></A> is useful.</P> <!-- Written by Tony Finch ([EMAIL PROTECTED]) ([EMAIL PROTECTED]). Some examples were derived from Ralf S. Engleschall's document http://www.engelschall.com/pw/apache/rewriteguide/ Some suggestions were made by Brian Behlendorf. --> <H2><A NAME="contents">Contents:</A></H2> <UL> <LI><A HREF="#motivation">Motivation</A> <LI><A HREF="#overview">Overview of the technique</A> <LI><A HREF="#simple">Simple name-based dynamic virtual hosts</A> <LI><A HREF="#homepages">A virtually hosted homepages system</A> <LI><A HREF="#xtra-conf">Using a separate virtual host configuration file</A> <LI><A HREF="#combinations">Using more than one virtual hosting system on the same server</A> </UL> <HR><H2><A NAME="motivation">Motivation</A></H2> <P>The techniques described here are of interest if your <CODE>httpd.conf</CODE> contains hundreds of <CODE><VirtualHost></CODE> sections that are substantially the same, for example: <PRE> NameVirtualHost 111.22.33.44 <VirtualHost 111.22.33.44> ServerName www.customer-1.com DocumentRoot /www/hosts/www.customer-1.com/docs ScriptAlias /cgi-bin/ /www/hosts/www.customer-1.com/cgi-bin </VirtualHost> <VirtualHost 111.22.33.44> ServerName www.customer-2.com DocumentRoot /www/hosts/www.customer-2.com/docs ScriptAlias /cgi-bin/ /www/hosts/www.customer-2.com/cgi-bin </VirtualHost> # blah blah blah <VirtualHost 111.22.33.44> ServerName www.customer-N.com DocumentRoot /www/hosts/www.customer-N.com/docs ScriptAlias /cgi-bin/ /www/hosts/www.customer-N.com/cgi-bin </VirtualHost> </PRE> </P> <P>The basic idea is to replace all of the static <CODE><VirtualHost></CODE> configuration with a mechanism that works it out dynamically. This has a number of advantages: <OL> <LI>Your configuration file is smaller so Apache starts faster and uses less memory. <LI>Adding virtual hosts is simply a matter of creating the appropriate directories in the filesystem and entries in the DNS - you don't need to reconfigure or restart Apache. </OL> </P> <P>The main disadvantage is that you cannot have a different log file for each server; however if you have very many virtual hosts then doing this is dubious anyway because it eats file descriptors. It's better to log to a pipe or a fifo and arrange for the process at the other end to distribute the logs (and perhaps accumulate statistics, etc.). A <CODE>LogFormat</CODE> directive that includes <CODE>%v</CODE> for the virtual host makes it easy to do this.</P> <HR><H2><A NAME="overview">Overview of the technique</A></H2> <P>All of the dynamic virtual hosts will either be configured as part of the main server configuration, or within a <CODE><VirtualHost></CODE> section. For a simple (very uniform) setup, <CODE><VirtualHost></CODE> sections aren't needed at all.</P> <P>A couple of things need to be `faked' to make the dynamic virtual host look like a normal one. The most important is the server name (configured with <CODE>ServerName</CODE> and available to CGIs via the <CODE>SERVER_NAME</CODE> environment variable). The way it is determined is controlled by the <CODE>UseCanonicalName</CODE> directive: with <CODE>UseCanonicalName off</CODE> the server name comes from the contents of the <CODE>Host:</CODE> header in the request. If there is no <CODE>Host:</CODE> header then the value configured with <CODE>ServerName</CODE> is used instead.</P> <P>The other one is the document root (configured with <CODE>DocumentRoot</CODE> and available to CGIs via the <CODE>DOCUMENT_ROOT</CODE> environment variable). This is used by the core module when mapping URIs to filenames, but in the context of dynamic virtual hosting its value only matters if any CGIs or SSI documents make use of the <CODE>DOCUMENT_ROOT</CODE> environment variable. This is an Apache extension to the CGI specification and as such shouldn't really be relied upon, especially because this technique breaks it: there isn't currently a way of setting <CODE>DOCUMENT_ROOT</CODE> dynamically.</P> <P>The meat of the mechanism works via Apache's URI-to-filename translation API phase. This is used by a number of modules: <A HREF="../mod/mod_rewrite.html"><CODE>mod_rewrite</CODE></A>, <A HREF="../mod/mod_alias.html"><CODE>mod_alias</CODE></A>, <A HREF="../mod/mod_userdir.html"><CODE>mod_userdir</CODE></A>, and <A HREF="../mod/core.html">the core module</A>. In the default configuration these modules are called in that order and given a chance to say that they know what the filename is. Most of these modules do it in a fairly simple fashion (e.g. the core module concatenates the document root and the URI) except for <CODE>mod_rewrite</CODE>, which provides enough functionality to do all sorts of sick and twisted things (like dynamic virtual hosting). Note that because of the order in which the modules are called, using a <CODE>mod_rewrite</CODE> configuration that matches any URI means that the other modules (particularly <CODE>mod_alias</CODE>) will cease to function. The examples below show how to deal with this.</P> <P><STRONG>The dynamic virtual hosting idea is very simple: use the server name as well as the URI to determine the corresponding filename.</STRONG></P> <HR><H2><A NAME="simple">Simple name-based dynamic virtual hosts</A></H2> <P>This extract from <CODE>httpd.conf</CODE> implements the virtual host arrangement outlined in the <A HREF="#motivation">Motivation</A> section above, but in a generic fashion.</P> <P>The first half shows some other configuration options that are needed to make the <CODE>mod_rewrite</CODE> part work as expected; the second half uses <CODE>mod_rewrite</CODE> to do the actual work. Some care is taken to do a per-dynamic-virtual-host equivalent of <CODE>ScriptAlias</CODE>.</P> <PRE> # dynamic ServerName UseCanonicalName Off # splittable logs LogFormat "%v %h %l %u %t \"%r\" %s %b" vcommon CustomLog logs/access_log vcommon <Directory /www/hosts> # ExecCGI is needed here because we can't force # CGI execution in the way that ScriptAlias does Options FollowSymLinks ExecCGI </Directory> # now for the hard bit RewriteEngine On # a ServerName derived from a Host: header may be any case at all RewriteMap lowercase int:tolower ## deal with normal documents first: # allow Alias /icons/ to work - repeat for other aliases RewriteCond %{REQUEST_URI} !^/icons/ # allow CGIs to work RewriteCond %{REQUEST_URI} !^/cgi-bin/ # do the magic RewriteRule ^/(.*)$ /www/hosts/${lowercase:%{SERVER_NAME}}/docs/$1 ## and now deal with CGIs - we have to force a MIME type RewriteCond %{REQUEST_URI} ^/cgi-bin/ RewriteRule ^/(.*)$ /www/hosts/${lowercase:%{SERVER_NAME}}/cgi-bin/$1 [T=application/x-httpd-cgi] # that's it! </PRE> <HR><H2><A NAME="homepages">A virtually hosted homepages system</A></H2> <P>This is an adjustment of the above system tailored for an ISP's homepages server. Using slightly more complicated rewriting rules we can select substrings of the server name to use in the filename so that e.g. the documents for <SAMP>www.user.isp.com</SAMP> are found in <CODE>/home/user/</CODE>. It uses a single <CODE>cgi-bin</CODE> directory instead of one per virtual host.</P> <PRE> RewriteEngine on RewriteMap lowercase int:tolower # allow CGIs to work RewriteCond %{REQUEST_URI} !^/cgi-bin/ # check the hostname is right so that the RewriteRule works RewriteCond ${lowercase:%{HTTP_HOST}} ^www\.[a-z-]+\.isp\.com$ # concatenate the virtual host name onto the start of the URI # the [C] means do the next rewrite on the result of this one RewriteRule ^(.+) ${lowercase:%{HTTP_HOST}}$1 [C] # now create the real file name RewriteRule ^www\.([a-z-]+)\.isp\.com/(.*) /home/$1/$2 # define the global CGI directory ScriptAlias /cgi-bin/ /www/std-cgi/ </PRE> <HR><H2><A NAME="xtra-conf">Using a separate virtual host configuration file</A></H2> <P>This arrangement uses a separate configuration file to specify the translation from virtual host to document root. This provides more flexibility but requires more configuration.</P> <P>The <CODE>vhost.map</CODE> file contains something like this: <PRE> www.customer-1.com /www/customers/1 www.customer-2.com /www/customers/2 # ... www.customer-N.com /www/customers/N </PRE> </P> <P>The <CODE>http.conf</CODE> contains this: <PRE> RewriteEngine on RewriteMap lowercase int:tolower # define the map file RewriteMap vhost txt:/www/conf/vhost.map # deal with aliases as above RewriteCond %{REQUEST_URI} !^/icons/ RewriteCond %{REQUEST_URI} !^/cgi-bin/ RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$ # this does the file-based remap RewriteCond ${vhost:%1} ^(/.*)$ RewriteRule ^/(.*)$ %1/docs/$1 RewriteCond %{REQUEST_URI} ^/cgi-bin/ RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$ RewriteCond ${vhost:%1} ^(/.*)$ RewriteRule ^/(.*)$ %1/cgi-bin/$1 </PRE> </P> <HR><H2><A NAME="combinations">Using more than one virtual hosting system on the same server</A></H2> <P>With more complicated setups, you can use Apache's normal <CODE><VirtualHost></CODE> directives to control the scope of the various rewrite configurations. For example, you could have one IP address for homepages customers and another for commercial customers with the following setup. This can of course be combined with convential <CODE><VirtualHost></CODE> configuration sections.</P> <PRE> UseCanonicalName Off LogFormat "%v %h %l %u %t \"%r\" %s %b" vcommon CustomLog logs/access_log vcommon <Directory /www/commercial> Options FollowSymLinks ExecCGI AllowOverride All </Directory> <Directory /www/homepages> Options FollowSymLinks AllowOverride None </Directory> <VirtualHost 111.22.33.44> ServerName www.commercial.isp.com RewriteEngine On RewriteMap lowercase int:tolower RewriteCond %{REQUEST_URI} !^/icons/ RewriteCond %{REQUEST_URI} !^/cgi-bin/ RewriteRule ^/(.*)$ /www/commercial/${lowercase:%{SERVER_NAME}}/docs/$1 RewriteCond %{REQUEST_URI} ^/cgi-bin/ RewriteRule ^/(.*)$ /www/commercial/${lowercase:%{SERVER_NAME}}/cgi-bin/$1 [T=application/x-httpd-cgi] </VirtualHost> <VirtualHost 111.22.33.45> ServerName www.homepages.isp.com RewriteEngine on RewriteMap lowercase int:tolower RewriteCond %{REQUEST_URI} !^/cgi-bin/ RewriteCond ${lowercase:%{HTTP_HOST}} ^www\.[a-z-]+\.isp\.com$ RewriteRule ^(.+) ${lowercase:%{HTTP_HOST}}$1 [C] RewriteRule ^www\.([a-z-]+)\.isp\.com/(.*) /www/homepages/$1/$2 ScriptAlias /cgi-bin/ /www/std-cgi/ </VirtualHost> </PRE> <HR> <H3 ALIGN="CENTER"> Apache HTTP Server Version 1.3 </H3> <A HREF="./"><IMG SRC="../images/index.gif" ALT="Index"></A> <A HREF="../"><IMG SRC="../images/home.gif" ALT="Home"></A> </BODY> </HTML>