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diff --git a/docs/manual/vhosts/mass.xml b/docs/manual/vhosts/mass.xml new file mode 100644 index 0000000000..e2aaad9761 --- /dev/null +++ b/docs/manual/vhosts/mass.xml @@ -0,0 +1,420 @@ +<?xml version='1.0' encoding='UTF-8' ?> +<!DOCTYPE manualpage SYSTEM "../style/manualpage.dtd"> +<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?> + +<manualpage> +<relativepath href=".."/> + + <title>Dynamically configured mass virtual hosting</title> + +<summary> + + <p>This document describes how to efficiently serve an + arbitrary number of virtual hosts with Apache 1.3. <!-- + + Written by Tony Finch (fanf@demon.net) (dot@dotat.at). + + Some examples were derived from Ralf S. Engleschall's document + http://www.engelschall.com/pw/apache/rewriteguide/ + + Some suggestions were made by Brian Behlendorf. + + --> + </p> + +</summary> + +<section id="motivation"><title>Motivation</title> + + <p>The techniques described here are of interest if your + <code>httpd.conf</code> contains many + <code><VirtualHost></code> sections that are + substantially the same, for example:</p> + +<example> +NameVirtualHost 111.22.33.44<br /> +<VirtualHost 111.22.33.44><br /> +<indent> + ServerName www.customer-1.com<br /> + DocumentRoot /www/hosts/www.customer-1.com/docs<br /> + ScriptAlias /cgi-bin/ /www/hosts/www.customer-1.com/cgi-bin<br /> +</indent> +</VirtualHost><br /> +<VirtualHost 111.22.33.44><br /> +<indent> + ServerName www.customer-2.com<br /> + DocumentRoot /www/hosts/www.customer-2.com/docs<br /> + ScriptAlias /cgi-bin/ /www/hosts/www.customer-2.com/cgi-bin<br /> +</indent> +</VirtualHost><br /> +# blah blah blah<br /> +<VirtualHost 111.22.33.44><br /> +<indent> + ServerName www.customer-N.com<br /> + DocumentRoot /www/hosts/www.customer-N.com/docs<br /> + ScriptAlias /cgi-bin/ /www/hosts/www.customer-N.com/cgi-bin<br /> +</indent> +</VirtualHost> +</example> + + <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:</p> + + <ol> + <li>Your configuration file is smaller so Apache starts + faster and uses less memory.</li> + + <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.</li> + </ol> + + <p>The main disadvantage is that you cannot have a different + log file for each virtual host; however if you have very many + virtual hosts then doing this is dubious anyway because it eats + file descriptors. It is better to log to a pipe or a fifo and + arrange for the process at the other end to distribute the logs + to the customers (it can also accumulate statistics, etc.).</p> + +</section> + +<section id="overview"><title>Overview</title> + + <p>A virtual host is defined by two pieces of information: its + IP address, and the contents of the <code>Host:</code> header + in the HTTP request. The dynamic mass virtual hosting technique + is based on automatically inserting this information into the + pathname of the file that is used to satisfy the request. This + is done most easily using <module>mod_vhost_alias</module>, + but if you are using a version of Apache up to 1.3.6 then you + must use <module>mod_rewrite</module>. + Both of these modules are disabled by default; you must enable + one of them when configuring and building Apache if you want to + use this technique.</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 which is used by Apache to generate + self-referential URLs, etc. It is configured with the + <code>ServerName</code> directive, and it is available to CGIs + via the <code>SERVER_NAME</code> environment variable. The + actual value used at run time is controlled by the <directive + module="core">UseCanonicalName</directive> + setting. With <code>UseCanonicalName Off</code> the server name + comes from the contents of the <code>Host:</code> header in the + request. With <code>UseCanonicalName DNS</code> it comes from a + reverse DNS lookup of the virtual host's IP address. The former + setting is used for name-based dynamic virtual hosting, and the + latter is used for IP-based hosting. If Apache cannot work out + the server name because there is no <code>Host:</code> header + or the DNS lookup fails then the value configured with + <code>ServerName</code> is used instead.</p> + + <p>The other thing to `fake' is the document root (configured + with <code>DocumentRoot</code> and available to CGIs via the + <code>DOCUMENT_ROOT</code> environment variable). In a normal + configuration this setting is used by the core module when + mapping URIs to filenames, but when the server is configured to + do dynamic virtual hosting that job is taken over by another + module (either <code>mod_vhost_alias</code> or + <code>mod_rewrite</code>) which has a different way of doing + the mapping. Neither of these modules is responsible for + setting the <code>DOCUMENT_ROOT</code> environment variable so + if any CGIs or SSI documents make use of it they will get a + misleading value.</p> + +</section> + +<section id="simple"><title>Simple dynamic virtual hosts</title> + + <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 using <code>mod_vhost_alias</code>.</p> + +<example> +# get the server name from the Host: header<br /> +UseCanonicalName Off<br /> +<br /> +# this log format can be split per-virtual-host based on the first field<br /> +LogFormat "%V %h %l %u %t \"%r\" %s %b" vcommon<br /> +CustomLog logs/access_log vcommon<br /> +<br /> +# include the server name in the filenames used to satisfy requests<br /> +VirtualDocumentRoot /www/hosts/%0/docs<br /> +VirtualScriptAlias /www/hosts/%0/cgi-bin +</example> + + <p>This configuration can be changed into an IP-based virtual + hosting solution by just turning <code>UseCanonicalName + Off</code> into <code>UseCanonicalName DNS</code>. The server + name that is inserted into the filename is then derived from + the IP address of the virtual host.</p> + +</section> + +<section id="homepages"><title>A virtually hosted homepages system</title> + + <p>This is an adjustment of the above system tailored for an + ISP's homepages server. Using a slightly more complicated + configuration 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> + +<example> +# all the preliminary stuff is the same as above, then<br /> +<br /> +# include part of the server name in the filenames<br /> +VirtualDocumentRoot /www/hosts/%2/docs<br /> +<br /> +# single cgi-bin directory<br /> +ScriptAlias /cgi-bin/ /www/std-cgi/<br /> +</example> + + <p>There are examples of more complicated + <code>VirtualDocumentRoot</code> settings in the + <module>mod_vhost_alias</module> documentation.</p> + +</section> + +<section id="combinations"><title>Using more than + one virtual hosting system on the same server</title> + + <p>With more complicated setups you can use Apache's normal + <code><VirtualHost></code> directives to control the + scope of the various virtual hosting 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 conventional + <code><VirtualHost></code> configuration sections.</p> + +<example> +UseCanonicalName Off<br /> +<br /> +LogFormat "%V %h %l %u %t \"%r\" %s %b" vcommon<br /> +<br /> +<Directory /www/commercial><br /> +<indent> + Options FollowSymLinks<br /> + AllowOverride All<br /> +</indent> +</Directory><br /> +<br /> +<Directory /www/homepages><br /> +<indent> + Options FollowSymLinks<br /> + AllowOverride None<br /> +</indent> +</Directory><br /> +<br /> +<VirtualHost 111.22.33.44><br /> +<indent> + ServerName www.commercial.isp.com<br /> + <br /> + CustomLog logs/access_log.commercial vcommon<br /> + <br /> + VirtualDocumentRoot /www/commercial/%0/docs<br /> + VirtualScriptAlias /www/commercial/%0/cgi-bin<br /> +</indent> +</VirtualHost><br /> +<br /> +<VirtualHost 111.22.33.45><br /> +<indent> + ServerName www.homepages.isp.com<br /> + <br /> + CustomLog logs/access_log.homepages vcommon<br /> + <br /> + VirtualDocumentRoot /www/homepages/%0/docs<br /> + ScriptAlias /cgi-bin/ /www/std-cgi/<br /> +</indent> +</VirtualHost> +</example> + +</section> + +<section id="ipbased"><title>More efficient IP-based virtual hosting</title> + + <p>After <a href="#simple">the first example</a> I noted that + it is easy to turn it into an IP-based virtual hosting setup. + Unfortunately that configuration is not very efficient because + it requires a DNS lookup for every request. This can be avoided + by laying out the filesystem according to the IP addresses + themselves rather than the corresponding names and changing the + logging similarly. Apache will then usually not need to work + out the server name and so incur a DNS lookup.</p> + +<example> +# get the server name from the reverse DNS of the IP address<br /> +UseCanonicalName DNS<br /> +<br /> +# include the IP address in the logs so they may be split<br /> +LogFormat "%A %h %l %u %t \"%r\" %s %b" vcommon<br /> +CustomLog logs/access_log vcommon<br /> +<br /> +# include the IP address in the filenames<br /> +VirtualDocumentRootIP /www/hosts/%0/docs<br /> +VirtualScriptAliasIP /www/hosts/%0/cgi-bin<br /> +</example> + +</section> + +<section id="oldversion"><title>Using older versions of Apache</title> + + <p>The examples above rely on <code>mod_vhost_alias</code> + which appeared after version 1.3.6. If you are using a version + of Apache without <code>mod_vhost_alias</code> then you can + implement this technique with <code>mod_rewrite</code> as + illustrated below, but only for Host:-header-based virtual + hosts.</p> + + <p>In addition there are some things to beware of with logging. + Apache 1.3.6 is the first version to include the + <code>%V</code> log format directive; in versions 1.3.0 - 1.3.3 + the <code>%v</code> option did what <code>%V</code> does; + version 1.3.4 has no equivalent. In all these versions of + Apache the <code>UseCanonicalName</code> directive can appear + in <code>.htaccess</code> files which means that customers can + cause the wrong thing to be logged. Therefore the best thing to + do is use the <code>%{Host}i</code> directive which logs the + <code>Host:</code> header directly; note that this may include + <code>:port</code> on the end which is not the case for + <code>%V</code>.</p> + +</section> + +<section id="simple.rewrite"><title>Simple dynamic + virtual hosts using <code>mod_rewrite</code></title> + + <p>This extract from <code>httpd.conf</code> does the same + thing as <a href="#simple">the first example</a>. The first + half is very similar to the corresponding part above but with + some changes for backward compatibility and to make the + <code>mod_rewrite</code> part work properly; the second half + configures <code>mod_rewrite</code> to do the actual work.</p> + + <p>There are a couple of especially tricky bits: By default, + <code>mod_rewrite</code> runs before the other URI translation + modules (<code>mod_alias</code> etc.) so if they are used then + <code>mod_rewrite</code> must be configured to accommodate + them. Also, mome magic must be performed to do a + per-dynamic-virtual-host equivalent of + <code>ScriptAlias</code>.</p> + +<example> +# get the server name from the Host: header<br /> +UseCanonicalName Off<br /> +<br /> +# splittable logs<br /> +LogFormat "%{Host}i %h %l %u %t \"%r\" %s %b" vcommon<br /> +CustomLog logs/access_log vcommon<br /> +<br /> +<Directory /www/hosts><br /> +<indent> + # ExecCGI is needed here because we can't force<br /> + # CGI execution in the way that ScriptAlias does<br /> + Options FollowSymLinks ExecCGI<br /> +</indent> +</Directory><br /> +<br /> +# now for the hard bit<br /> +<br /> +RewriteEngine On<br /> +<br /> +# a ServerName derived from a Host: header may be any case at all<br /> +RewriteMap lowercase int:tolower<br /> +<br /> +## deal with normal documents first:<br /> +# allow Alias /icons/ to work - repeat for other aliases<br /> +RewriteCond %{REQUEST_URI} !^/icons/<br /> +# allow CGIs to work<br /> +RewriteCond %{REQUEST_URI} !^/cgi-bin/<br /> +# do the magic<br /> +RewriteRule ^/(.*)$ /www/hosts/${lowercase:%{SERVER_NAME}}/docs/$1<br /> +<br /> +## and now deal with CGIs - we have to force a MIME type<br /> +RewriteCond %{REQUEST_URI} ^/cgi-bin/<br /> +RewriteRule ^/(.*)$ /www/hosts/${lowercase:%{SERVER_NAME}}/cgi-bin/$1 [T=application/x-httpd-cgi]<br /> +<br /> +# that's it! +</example> + +</section> + +<section id="homepages.rewrite"><title>A + homepages system using <code>mod_rewrite</code></title> + + <p>This does the same thing as <a href="#homepages">the second + example</a>.</p> + +<example> +RewriteEngine on<br /> +<br /> +RewriteMap lowercase int:tolower<br /> +<br /> +# allow CGIs to work<br /> +RewriteCond %{REQUEST_URI} !^/cgi-bin/<br /> +<br /> +# check the hostname is right so that the RewriteRule works<br /> +RewriteCond ${lowercase:%{SERVER_NAME}} ^www\.[a-z-]+\.isp\.com$<br /> +<br /> +# concatenate the virtual host name onto the start of the URI<br /> +# the [C] means do the next rewrite on the result of this one<br /> +RewriteRule ^(.+) ${lowercase:%{SERVER_NAME}}$1 [C]<br /> +<br /> +# now create the real file name<br /> +RewriteRule ^www\.([a-z-]+)\.isp\.com/(.*) /home/$1/$2<br /> +<br /> +# define the global CGI directory<br /> +ScriptAlias /cgi-bin/ /www/std-cgi/ +</example> + +</section> + +<section id="xtra-conf"><title>Using a separate virtual + host configuration file</title> + + <p>This arrangement uses more advanced <code>mod_rewrite</code> + features to get the translation from virtual host to document + root from a separate configuration file. This provides more + flexibility but requires more complicated configuration.</p> + + <p>The <code>vhost.map</code> file contains something like + this:</p> + +<example> +www.customer-1.com /www/customers/1<br /> +www.customer-2.com /www/customers/2<br /> +# ...<br /> +www.customer-N.com /www/customers/N<br /> +</example> + + <p>The <code>http.conf</code> contains this:</p> + +<example> +RewriteEngine on<br /> +<br /> +RewriteMap lowercase int:tolower<br /> +<br /> +# define the map file<br /> +RewriteMap vhost txt:/www/conf/vhost.map<br /> +<br /> +# deal with aliases as above<br /> +RewriteCond %{REQUEST_URI} !^/icons/<br /> +RewriteCond %{REQUEST_URI} !^/cgi-bin/<br /> +RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$<br /> +# this does the file-based remap<br /> +RewriteCond ${vhost:%1} ^(/.*)$<br /> +RewriteRule ^/(.*)$ %1/docs/$1<br /> +<br /> +RewriteCond %{REQUEST_URI} ^/cgi-bin/<br /> +RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$<br /> +RewriteCond ${vhost:%1} ^(/.*)$<br /> +RewriteRule ^/(.*)$ %1/cgi-bin/$1 +</example> + +</section> +</manualpage> |