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| author | (no author) <(no author)@unknown> | 2001-05-04 21:54:25 +0000 |
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| committer | (no author) <(no author)@unknown> | 2001-05-04 21:54:25 +0000 |
| commit | ad2dd84025f628d29200b5a9a41d654be678aa6f (patch) | |
| tree | 35a838b6e9d6510a91e386728e78b4a81cb55781 /docs/manual/misc/rewriteguide.html | |
| parent | f83672781de25207442ff908258219de1d103062 (diff) | |
| download | httpd-RSE.tar.gz | |
This commit was manufactured by cvs2svn to create branch 'RSE'.RSE
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/RSE@88989 13f79535-47bb-0310-9956-ffa450edef68
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diff --git a/docs/manual/misc/rewriteguide.html b/docs/manual/misc/rewriteguide.html deleted file mode 100644 index 0f469bd8b0..0000000000 --- a/docs/manual/misc/rewriteguide.html +++ /dev/null @@ -1,1906 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> -<HTML><HEAD> -<TITLE>Apache 1.3 URL Rewriting Guide</TITLE> -</HEAD> - -<!-- Background white, links blue (unvisited), navy (visited), red (active) --> -<BODY - BGCOLOR="#FFFFFF" - TEXT="#000000" - LINK="#0000FF" - VLINK="#000080" - ALINK="#FF0000" -> -<BLOCKQUOTE> -<!--#include virtual="header.html" --> - -<DIV ALIGN=CENTER> - -<H1> -Apache 1.3<BR> -URL Rewriting Guide<BR> -</H1> - -<ADDRESS>Originally written by<BR> -Ralf S. Engelschall <rse@apache.org><BR> -December 1997</ADDRESS> - -</DIV> - -<P> -This document supplements the mod_rewrite <A -HREF="../mod/mod_rewrite.html">reference documentation</A>. It describes -how one can use Apache's mod_rewrite to solve typical URL-based problems -webmasters are usually confronted with in practice. I give detailed -descriptions on how to solve each problem by configuring URL rewriting -rulesets. - -<H2><A name="ToC1">Introduction to mod_rewrite</A></H2> - -The Apache module mod_rewrite is a killer one, i.e. it is a really -sophisticated module which provides a powerful way to do URL manipulations. -With it you can nearly do all types of URL manipulations you ever dreamed -about. The price you have to pay is to accept complexity, because -mod_rewrite's major drawback is that it is not easy to understand and use for -the beginner. And even Apache experts sometimes discover new aspects where -mod_rewrite can help. -<P> -In other words: With mod_rewrite you either shoot yourself in the foot the -first time and never use it again or love it for the rest of your life because -of its power. This paper tries to give you a few initial success events to -avoid the first case by presenting already invented solutions to you. - -<H2><A name="ToC2">Practical Solutions</A></H2> - -Here come a lot of practical solutions I've either invented myself or -collected from other peoples solutions in the past. Feel free to learn the -black magic of URL rewriting from these examples. - -<P> -<TABLE BGCOLOR="#FFE0E0" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD> -ATTENTION: Depending on your server-configuration it can be necessary to -slightly change the examples for your situation, e.g. adding the [PT] flag -when additionally using mod_alias and mod_userdir, etc. Or rewriting a ruleset -to fit in <CODE>.htaccess</CODE> context instead of per-server context. Always try -to understand what a particular ruleset really does before you use it. It -avoid problems. -</TD></TR></TABLE> - -<H1>URL Layout</H1> - -<P> -<H2>Canonical URLs</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -On some webservers there are more than one URL for a resource. Usually there -are canonical URLs (which should be actually used and distributed) and those -which are just shortcuts, internal ones, etc. Independed which URL the user -supplied with the request he should finally see the canonical one only. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We do an external HTTP redirect for all non-canonical URLs to fix them in the -location view of the Browser and for all subsequent requests. In the example -ruleset below we replace <CODE>/~user</CODE> by the canonical <CODE>/u/user</CODE> and -fix a missing trailing slash for <CODE>/u/user</CODE>. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^/<STRONG>~</STRONG>([^/]+)/?(.*) /<STRONG>u</STRONG>/$1/$2 [<STRONG>R</STRONG>] -RewriteRule ^/([uge])/(<STRONG>[^/]+</STRONG>)$ /$1/$2<STRONG>/</STRONG> [<STRONG>R</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Canonical Hostnames</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -... - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC] -RewriteCond %{HTTP_HOST} !^$ -RewriteCond %{SERVER_PORT} !^80$ -RewriteRule ^/(.*) http://fully.qualified.domain.name:%{SERVER_PORT}/$1 [L,R] -RewriteCond %{HTTP_HOST} !^fully\.qualified\.domain\.name [NC] -RewriteCond %{HTTP_HOST} !^$ -RewriteRule ^/(.*) http://fully.qualified.domain.name/$1 [L,R] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Moved DocumentRoot</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Usually the DocumentRoot of the webserver directly relates to the URL -``<CODE>/</CODE>''. But often this data is not really of top-level priority, it is -perhaps just one entity of a lot of data pools. For instance at our Intranet -sites there are <CODE>/e/www/</CODE> (the homepage for WWW), <CODE>/e/sww/</CODE> (the -homepage for the Intranet) etc. Now because the data of the DocumentRoot stays -at <CODE>/e/www/</CODE> we had to make sure that all inlined images and other -stuff inside this data pool work for subsequent requests. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We just redirect the URL <CODE>/</CODE> to <CODE>/e/www/</CODE>. While is seems -trivial it is actually trivial with mod_rewrite, only. Because the typical -old mechanisms of URL <EM>Aliases</EM> (as provides by mod_alias and friends) -only used <EM>prefix</EM> matching. With this you cannot do such a redirection -because the DocumentRoot is a prefix of all URLs. With mod_rewrite it is -really trivial: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteRule <STRONG>^/$</STRONG> /e/www/ [<STRONG>R</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Trailing Slash Problem</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Every webmaster can sing a song about the problem of the trailing slash on -URLs referencing directories. If they are missing, the server dumps an error, -because if you say <CODE>/~quux/foo</CODE> instead of -<CODE>/~quux/foo/</CODE> then the server searches for a <EM>file</EM> named -<CODE>foo</CODE>. And because this file is a directory it complains. Actually -is tries to fix it themself in most of the cases, but sometimes this mechanism -need to be emulated by you. For instance after you have done a lot of -complicated URL rewritings to CGI scripts etc. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -The solution to this subtle problem is to let the server add the trailing -slash automatically. To do this correctly we have to use an external redirect, -so the browser correctly requests subsequent images etc. If we only did a -internal rewrite, this would only work for the directory page, but would go -wrong when any images are included into this page with relative URLs, because -the browser would request an in-lined object. For instance, a request for -<CODE>image.gif</CODE> in <CODE>/~quux/foo/index.html</CODE> would become -<CODE>/~quux/image.gif</CODE> without the external redirect! -<P> -So, to do this trick we write: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^foo<STRONG>$</STRONG> foo<STRONG>/</STRONG> [<STRONG>R</STRONG>] -</PRE></TD></TR></TABLE> - -<P> -The crazy and lazy can even do the following in the top-level -<CODE>.htaccess</CODE> file of their homedir. But notice that this creates some -processing overhead. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteCond %{REQUEST_FILENAME} <STRONG>-d</STRONG> -RewriteRule ^(.+<STRONG>[^/]</STRONG>)$ $1<STRONG>/</STRONG> [R] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Webcluster through Homogeneous URL Layout</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -We want to create a homogenous and consistent URL layout over all WWW servers -on a Intranet webcluster, i.e. all URLs (per definition server local and thus -server dependent!) become actually server <EM>independed</EM>! What we want is -to give the WWW namespace a consistent server-independend layout: no URL -should have to include any physically correct target server. The cluster -itself should drive us automatically to the physical target host. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -First, the knowledge of the target servers come from (distributed) external -maps which contain information where our users, groups and entities stay. -The have the form - -<P><PRE> -user1 server_of_user1 -user2 server_of_user2 -: : -</PRE><P> - -We put them into files <CODE>map.xxx-to-host</CODE>. Second we need to instruct -all servers to redirect URLs of the forms - -<P><PRE> -/u/user/anypath -/g/group/anypath -/e/entity/anypath -</PRE><P> - -to - -<P><PRE> -http://physical-host/u/user/anypath -http://physical-host/g/group/anypath -http://physical-host/e/entity/anypath -</PRE><P> - -when the URL is not locally valid to a server. The following ruleset does -this for us by the help of the map files (assuming that server0 is a default -server which will be used if a user has no entry in the map): - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on - -RewriteMap user-to-host txt:/path/to/map.user-to-host -RewriteMap group-to-host txt:/path/to/map.group-to-host -RewriteMap entity-to-host txt:/path/to/map.entity-to-host - -RewriteRule ^/u/<STRONG>([^/]+)</STRONG>/?(.*) http://<STRONG>${user-to-host:$1|server0}</STRONG>/u/$1/$2 -RewriteRule ^/g/<STRONG>([^/]+)</STRONG>/?(.*) http://<STRONG>${group-to-host:$1|server0}</STRONG>/g/$1/$2 -RewriteRule ^/e/<STRONG>([^/]+)</STRONG>/?(.*) http://<STRONG>${entity-to-host:$1|server0}</STRONG>/e/$1/$2 - -RewriteRule ^/([uge])/([^/]+)/?$ /$1/$2/.www/ -RewriteRule ^/([uge])/([^/]+)/([^.]+.+) /$1/$2/.www/$3\ -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Move Homedirs to Different Webserver</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -A lot of webmaster aksed for a solution to the following situation: They -wanted to redirect just all homedirs on a webserver to another webserver. -They usually need such things when establishing a newer webserver which will -replace the old one over time. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -The solution is trivial with mod_rewrite. On the old webserver we just -redirect all <CODE>/~user/anypath</CODE> URLs to -<CODE>http://newserver/~user/anypath</CODE>. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteRule ^/~(.+) http://<STRONG>newserver</STRONG>/~$1 [R,L] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Structured Homedirs</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Some sites with thousend of users usually use a structured homedir layout, -i.e. each homedir is in a subdirectory which begins for instance with the -first character of the username. So, <CODE>/~foo/anypath</CODE> is -<CODE>/home/<STRONG>f</STRONG>/foo/.www/anypath</CODE> while <CODE>/~bar/anypath</CODE> is -<CODE>/home/<STRONG>b</STRONG>/bar/.www/anypath</CODE>. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We use the following ruleset to expand the tilde URLs into exactly the above -layout. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteRule ^/~(<STRONG>([a-z])</STRONG>[a-z0-9]+)(.*) /home/<STRONG>$2</STRONG>/$1/.www$3 -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Filesystem Reorganisation</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -This really is a hardcore example: a killer application which heavily uses -per-directory <CODE>RewriteRules</CODE> to get a smooth look and feel on the Web -while its data structure is never touched or adjusted. - -Background: <STRONG><EM>net.sw</EM></STRONG> is my archive of freely available Unix -software packages, which I started to collect in 1992. It is both my hobby and -job to to this, because while I'm studying computer science I have also worked -for many years as a system and network administrator in my spare time. Every -week I need some sort of software so I created a deep hierarchy of -directories where I stored the packages: - -<P><PRE> -drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/ -drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/ -drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/ -drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/ -drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/ -drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/ -drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/ -drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/ -drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/ -drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/ -drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/ -drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/ -drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/ -drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/ -drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/ -drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/ -</PRE><P> - -In July 1996 I decided to make this archive public to the world via a -nice Web interface. "Nice" means that I wanted to -offer an interface where you can browse directly through the archive hierarchy. -And "nice" means that I didn't wanted to change anything inside this hierarchy -- not even by putting some CGI scripts at the top of it. Why? Because the -above structure should be later accessible via FTP as well, and I didn't -want any Web or CGI stuff to be there. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -The solution has two parts: The first is a set of CGI scripts which create all -the pages at all directory levels on-the-fly. I put them under -<CODE>/e/netsw/.www/</CODE> as follows: - -<P><PRE> --rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl -drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/ --rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE --rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO --rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html --rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl --rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi --rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi -drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/ --rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi --rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi --rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi --rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst -</PRE><P> - -The <CODE>DATA/</CODE> subdirectory holds the above directory structure, i.e. the -real <STRONG><EM>net.sw</EM></STRONG> stuff and gets automatically updated via -<CODE>rdist</CODE> from time to time. - -The second part of the problem remains: how to link these two structures -together into one smooth-looking URL tree? We want to hide the <CODE>DATA/</CODE> -directory from the user while running the appropriate CGI scripts for the -various URLs. - -Here is the solution: first I put the following into the per-directory -configuration file in the Document Root of the server to rewrite the announced -URL <CODE>/net.sw/</CODE> to the internal path <CODE>/e/netsw</CODE>: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^net.sw$ net.sw/ [R] -RewriteRule ^net.sw/(.*)$ e/netsw/$1 -</PRE></TD></TR></TABLE> - -<P> -The first rule is for requests which miss the trailing slash! The second rule -does the real thing. And then comes the killer configuration which stays in -the per-directory config file <CODE>/e/netsw/.www/.wwwacl</CODE>: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -Options ExecCGI FollowSymLinks Includes MultiViews - -RewriteEngine on - -# we are reached via /net.sw/ prefix -RewriteBase /net.sw/ - -# first we rewrite the root dir to -# the handling cgi script -RewriteRule ^$ netsw-home.cgi [L] -RewriteRule ^index\.html$ netsw-home.cgi [L] - -# strip out the subdirs when -# the browser requests us from perdir pages -RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L] - -# and now break the rewriting for local files -RewriteRule ^netsw-home\.cgi.* - [L] -RewriteRule ^netsw-changes\.cgi.* - [L] -RewriteRule ^netsw-search\.cgi.* - [L] -RewriteRule ^netsw-tree\.cgi$ - [L] -RewriteRule ^netsw-about\.html$ - [L] -RewriteRule ^netsw-img/.*$ - [L] - -# anything else is a subdir which gets handled -# by another cgi script -RewriteRule !^netsw-lsdir\.cgi.* - [C] -RewriteRule (.*) netsw-lsdir.cgi/$1 -</PRE></TD></TR></TABLE> - -<P> -Some hints for interpretation: - <ol> - <li> Notice the L (last) flag and no substitution field ('-') in the - forth part - <li> Notice the ! (not) character and the C (chain) flag - at the first rule in the last part - <li> Notice the catch-all pattern in the last rule - </ol> - -</DL> - -<P> -<H2>NCSA imagemap to Apache mod_imap</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -When switching from the NCSA webserver to the more modern Apache webserver a -lot of people want a smooth transition. So they want pages which use their old -NCSA <CODE>imagemap</CODE> program to work under Apache with the modern -<CODE>mod_imap</CODE>. The problem is that there are a lot of -hyperlinks around which reference the <CODE>imagemap</CODE> program via -<CODE>/cgi-bin/imagemap/path/to/page.map</CODE>. Under Apache this -has to read just <CODE>/path/to/page.map</CODE>. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We use a global rule to remove the prefix on-the-fly for all requests: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteRule ^/cgi-bin/imagemap(.*) $1 [PT] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Search pages in more than one directory</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Sometimes it is neccessary to let the webserver search for pages in more than -one directory. Here MultiViews or other techniques cannot help. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We program a explicit ruleset which searches for the files in the directories. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on - -# first try to find it in custom/... -# ...and if found stop and be happy: -RewriteCond /your/docroot/<STRONG>dir1</STRONG>/%{REQUEST_FILENAME} -f -RewriteRule ^(.+) /your/docroot/<STRONG>dir1</STRONG>/$1 [L] - -# second try to find it in pub/... -# ...and if found stop and be happy: -RewriteCond /your/docroot/<STRONG>dir2</STRONG>/%{REQUEST_FILENAME} -f -RewriteRule ^(.+) /your/docroot/<STRONG>dir2</STRONG>/$1 [L] - -# else go on for other Alias or ScriptAlias directives, -# etc. -RewriteRule ^(.+) - [PT] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Set Environment Variables According To URL Parts</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Perhaps you want to keep status information between requests and use the URL -to encode it. But you don't want to use a CGI wrapper for all pages just to -strip out this information. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We use a rewrite rule to strip out the status information and remember it via -an environment variable which can be later dereferenced from within XSSI or -CGI. This way a URL <CODE>/foo/S=java/bar/</CODE> gets translated to -<CODE>/foo/bar/</CODE> and the environment variable named <CODE>STATUS</CODE> is set -to the value "java". - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteRule ^(.*)/<STRONG>S=([^/]+)</STRONG>/(.*) $1/$3 [E=<STRONG>STATUS:$2</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Virtual User Hosts</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Assume that you want to provide <CODE>www.<STRONG>username</STRONG>.host.domain.com</CODE> -for the homepage of username via just DNS A records to the same machine and -without any virtualhosts on this machine. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -For HTTP/1.0 requests there is no solution, but for HTTP/1.1 requests which -contain a Host: HTTP header we can use the following ruleset to rewrite -<CODE>http://www.username.host.com/anypath</CODE> internally to -<CODE>/home/username/anypath</CODE>: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond %{<STRONG>HTTP_HOST</STRONG>} ^www\.<STRONG>[^.]+</STRONG>\.host\.com$ -RewriteRule ^(.+) %{HTTP_HOST}$1 [C] -RewriteRule ^www\.<STRONG>([^.]+)</STRONG>\.host\.com(.*) /home/<STRONG>$1</STRONG>$2 -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Redirect Homedirs For Foreigners</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -We want to redirect homedir URLs to another webserver -<CODE>www.somewhere.com</CODE> when the requesting user does not stay in the local -domain <CODE>ourdomain.com</CODE>. This is sometimes used in virtual host -contexts. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -Just a rewrite condition: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond %{REMOTE_HOST} <STRONG>!^.+\.ourdomain\.com$</STRONG> -RewriteRule ^(/~.+) http://www.somewhere.com/$1 [R,L] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Redirect Failing URLs To Other Webserver</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -A typical FAQ about URL rewriting is how to redirect failing requests on -webserver A to webserver B. Usually this is done via ErrorDocument -CGI-scripts in Perl, but there is also a mod_rewrite solution. But notice that -this is less performant than using a ErrorDocument CGI-script! - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -The first solution has the best performance but less flexibility and is less -error safe: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond /your/docroot/%{REQUEST_FILENAME} <STRONG>!-f</STRONG> -RewriteRule ^(.+) http://<STRONG>webserverB</STRONG>.dom/$1 -</PRE></TD></TR></TABLE> - -<P> -The problem here is that this will only work for pages inside the -DocumentRoot. While you can add more Conditions (for instance to also handle -homedirs, etc.) there is better variant: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond %{REQUEST_URI} <STRONG>!-U</STRONG> -RewriteRule ^(.+) http://<STRONG>webserverB</STRONG>.dom/$1 -</PRE></TD></TR></TABLE> - -<P> -This uses the URL look-ahead feature of mod_rewrite. The result is that this -will work for all types of URLs and is a safe way. But it does a performance -impact on the webserver, because for every request there is one more internal -subrequest. So, if your webserver runs on a powerful CPU, use this one. If it -is a slow machine, use the first approach or better a ErrorDocument -CGI-script. - -</DL> - -<P> -<H2>Extended Redirection</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Sometimes we need more control (concerning the character escaping mechanism) -of URLs on redirects. Usually the Apache kernels URL escape function also -escapes anchors, i.e. URLs like "url#anchor". You cannot use this directly on -redirects with mod_rewrite because the uri_escape() function of Apache would -also escape the hash character. How can we redirect to such a URL? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We have to use a kludge by the use of a NPH-CGI script which does the redirect -itself. Because here no escaping is done (NPH=non-parseable headers). First -we introduce a new URL scheme <CODE>xredirect:</CODE> by the following per-server -config-line (should be one of the last rewrite rules): - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^xredirect:(.+) /path/to/nph-xredirect.cgi/$1 \ - [T=application/x-httpd-cgi,L] -</PRE></TD></TR></TABLE> - -<P> -This forces all URLs prefixed with <CODE>xredirect:</CODE> to be piped through the -<CODE>nph-xredirect.cgi</CODE> program. And this program just looks like: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -<PRE> -#!/path/to/perl -## -## nph-xredirect.cgi -- NPH/CGI script for extended redirects -## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved. -## - -$| = 1; -$url = $ENV{'PATH_INFO'}; - -print "HTTP/1.0 302 Moved Temporarily\n"; -print "Server: $ENV{'SERVER_SOFTWARE'}\n"; -print "Location: $url\n"; -print "Content-type: text/html\n"; -print "\n"; -print "<html>\n"; -print "<head>\n"; -print "<title>302 Moved Temporarily (EXTENDED)</title>\n"; -print "</head>\n"; -print "<body>\n"; -print "<h1>Moved Temporarily (EXTENDED)</h1>\n"; -print "The document has moved <a HREF=\"$url\">here</a>.<p>\n"; -print "</body>\n"; -print "</html>\n"; - -##EOF## -</PRE> -</PRE></TD></TR></TABLE> - -<P> -This provides you with the functionality to do redirects to all URL schemes, -i.e. including the one which are not directly accepted by mod_rewrite. For -instance you can now also redirect to <CODE>news:newsgroup</CODE> via - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^anyurl xredirect:news:newsgroup -</PRE></TD></TR></TABLE> - -<P> -Notice: You have not to put [R] or [R,L] to the above rule because the -<CODE>xredirect:</CODE> need to be expanded later by our special "pipe through" -rule above. - -</DL> - -<P> -<H2>Archive Access Multiplexer</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Do you know the great CPAN (Comprehensive Perl Archive Network) under <A -HREF="http://www.perl.com/CPAN">http://www.perl.com/CPAN</A>? This does a -redirect to one of several FTP servers around the world which carry a CPAN -mirror and is approximately near the location of the requesting client. -Actually this can be called an FTP access multiplexing service. While CPAN -runs via CGI scripts, how can a similar approach implemented via mod_rewrite? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -First we notice that from version 3.0.0 mod_rewrite can also use the "ftp:" -scheme on redirects. And second, the location approximation can be done by a -rewritemap over the top-level domain of the client. With a tricky chained -ruleset we can use this top-level domain as a key to our multiplexing map. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteMap multiplex txt:/path/to/map.cxan -RewriteRule ^/CxAN/(.*) %{REMOTE_HOST}::$1 [C] -RewriteRule ^.+\.<STRONG>([a-zA-Z]+)</STRONG>::(.*)$ ${multiplex:<STRONG>$1</STRONG>|ftp.default.dom}$2 [R,L] -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## map.cxan -- Multiplexing Map for CxAN -## - -de ftp://ftp.cxan.de/CxAN/ -uk ftp://ftp.cxan.uk/CxAN/ -com ftp://ftp.cxan.com/CxAN/ - : -##EOF## -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Time-Dependend Rewriting</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -When tricks like time-dependend content should happen a lot of webmasters -still use CGI scripts which do for instance redirects to specialized pages. -How can it be done via mod_rewrite? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -There are a lot of variables named <CODE>TIME_xxx</CODE> for rewrite conditions. -In conjunction with the special lexicographic comparison patterns <STRING, ->STRING and =STRING we can do time-dependend redirects: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700 -RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900 -RewriteRule ^foo\.html$ foo.day.html -RewriteRule ^foo\.html$ foo.night.html -</PRE></TD></TR></TABLE> - -<P> -This provides the content of <CODE>foo.day.html</CODE> under the URL -<CODE>foo.html</CODE> from 07:00-19:00 and at the remaining time the contents of -<CODE>foo.night.html</CODE>. Just a nice feature for a homepage... - -</DL> - -<P> -<H2>Backward Compatibility for YYYY to XXXX migration</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we make URLs backward compatible (still existing virtually) after -migrating document.YYYY to document.XXXX, e.g. after translating a bunch of -.html files to .phtml? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We just rewrite the name to its basename and test for existence of the new -extension. If it exists, we take that name, else we rewrite the URL to its -original state. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -# backward compatibility ruleset for -# rewriting document.html to document.phtml -# when and only when document.phtml exists -# but no longer document.html -RewriteEngine on -RewriteBase /~quux/ -# parse out basename, but remember the fact -RewriteRule ^(.*)\.html$ $1 [C,E=WasHTML:yes] -# rewrite to document.phtml if exists -RewriteCond %{REQUEST_FILENAME}.phtml -f -RewriteRule ^(.*)$ $1.phtml [S=1] -# else reverse the previous basename cutout -RewriteCond %{ENV:WasHTML} ^yes$ -RewriteRule ^(.*)$ $1.html -</PRE></TD></TR></TABLE> - -</DL> - -<H1>Content Handling</H1> - -<P> -<H2>From Old to New (intern)</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Assume we have recently renamed the page <CODE>bar.html</CODE> to -<CODE>foo.html</CODE> and now want to provide the old URL for backward -compatibility. Actually we want that users of the old URL even not recognize -that the pages was renamed. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We rewrite the old URL to the new one internally via the following rule: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^<STRONG>foo</STRONG>\.html$ <STRONG>bar</STRONG>.html -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>From Old to New (extern)</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Assume again that we have recently renamed the page <CODE>bar.html</CODE> to -<CODE>foo.html</CODE> and now want to provide the old URL for backward -compatibility. But this time we want that the users of the old URL get hinted -to the new one, i.e. their browsers Location field should change, too. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We force a HTTP redirect to the new URL which leads to a change of the -browsers and thus the users view: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^<STRONG>foo</STRONG>\.html$ <STRONG>bar</STRONG>.html [<STRONG>R</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Browser Dependend Content</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -At least for important top-level pages it is sometimes necesarry to provide -the optimum of browser dependend content, i.e. one has to provide a maximum -version for the latest Netscape variants, a minimum version for the Lynx -browsers and a average feature version for all others. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We cannot use content negotiation because the browsers do not provide their -type in that form. Instead we have to act on the HTTP header "User-Agent". -The following condig does the following: If the HTTP header "User-Agent" -begins with "Mozilla/3", the page <CODE>foo.html</CODE> is rewritten to -<CODE>foo.NS.html</CODE> and and the rewriting stops. If the browser is "Lynx" or -"Mozilla" of version 1 or 2 the URL becomes <CODE>foo.20.html</CODE>. All other -browsers receive page <CODE>foo.32.html</CODE>. This is done by the following -ruleset: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{HTTP_USER_AGENT} ^<STRONG>Mozilla/3</STRONG>.* -RewriteRule ^foo\.html$ foo.<STRONG>NS</STRONG>.html [<STRONG>L</STRONG>] - -RewriteCond %{HTTP_USER_AGENT} ^<STRONG>Lynx/</STRONG>.* [OR] -RewriteCond %{HTTP_USER_AGENT} ^<STRONG>Mozilla/[12]</STRONG>.* -RewriteRule ^foo\.html$ foo.<STRONG>20</STRONG>.html [<STRONG>L</STRONG>] - -RewriteRule ^foo\.html$ foo.<STRONG>32</STRONG>.html [<STRONG>L</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Dynamic Mirror</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Assume there are nice webpages on remote hosts we want to bring into our -namespace. For FTP servers we would use the <CODE>mirror</CODE> program which -actually maintains an explicit up-to-date copy of the remote data on the local -machine. For a webserver we could use the program <CODE>webcopy</CODE> which acts -similar via HTTP. But both techniques have one major drawback: The local copy -is always just as up-to-date as often we run the program. It would be much -better if the mirror is not a static one we have to establish explicitly. -Instead we want a dynamic mirror with data which gets updated automatically -when there is need (updated data on the remote host). - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -To provide this feature we map the remote webpage or even the complete remote -webarea to our namespace by the use of the <I>Proxy Throughput</I> feature -(flag [P]): - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^<STRONG>hotsheet/</STRONG>(.*)$ <STRONG>http://www.tstimpreso.com/hotsheet/</STRONG>$1 [<STRONG>P</STRONG>] -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^<STRONG>usa-news\.html</STRONG>$ <STRONG>http://www.quux-corp.com/news/index.html</STRONG> [<STRONG>P</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Reverse Dynamic Mirror</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -... - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteCond /mirror/of/remotesite/$1 -U -RewriteRule ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1 -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Retrieve Missing Data from Intranet</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -This is a tricky way of virtually running a corporates (external) Internet -webserver (<CODE>www.quux-corp.dom</CODE>), while actually keeping and maintaining -its data on a (internal) Intranet webserver -(<CODE>www2.quux-corp.dom</CODE>) which is protected by a firewall. The -trick is that on the external webserver we retrieve the requested data -on-the-fly from the internal one. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -First, we have to make sure that our firewall still protects the internal -webserver and that only the external webserver is allowed to retrieve data -from it. For a packet-filtering firewall we could for instance configure a -firewall ruleset like the following: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -<STRONG>ALLOW</STRONG> Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port <STRONG>80</STRONG> -<STRONG>DENY</STRONG> Host * Port * --> Host www2.quux-corp.dom Port <STRONG>80</STRONG> -</PRE></TD></TR></TABLE> - -<P> -Just adjust it to your actual configuration syntax. Now we can establish the -mod_rewrite rules which request the missing data in the background through the -proxy throughput feature: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^/~([^/]+)/?(.*) /home/$1/.www/$2 -RewriteCond %{REQUEST_FILENAME} <STRONG>!-f</STRONG> -RewriteCond %{REQUEST_FILENAME} <STRONG>!-d</STRONG> -RewriteRule ^/home/([^/]+)/.www/?(.*) http://<STRONG>www2</STRONG>.quux-corp.dom/~$1/pub/$2 [<STRONG>P</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Load Balancing</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Suppose we want to load balance the traffic to <CODE>www.foo.com</CODE> over -<CODE>www[0-5].foo.com</CODE> (a total of 6 servers). How can this be done? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -There are a lot of possible solutions for this problem. We will discuss first -a commonly known DNS-based variant and then the special one with mod_rewrite: - -<ol> -<li><STRONG>DNS Round-Robin</STRONG> - -<P> -The simplest method for load-balancing is to use the DNS round-robin feature -of BIND. Here you just configure <CODE>www[0-9].foo.com</CODE> as usual in your -DNS with A(address) records, e.g. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -www0 IN A 1.2.3.1 -www1 IN A 1.2.3.2 -www2 IN A 1.2.3.3 -www3 IN A 1.2.3.4 -www4 IN A 1.2.3.5 -www5 IN A 1.2.3.6 -</PRE></TD></TR></TABLE> - -<P> -Then you additionally add the following entry: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -www IN CNAME www0.foo.com. - IN CNAME www1.foo.com. - IN CNAME www2.foo.com. - IN CNAME www3.foo.com. - IN CNAME www4.foo.com. - IN CNAME www5.foo.com. - IN CNAME www6.foo.com. -</PRE></TD></TR></TABLE> - -<P> -Notice that this seems wrong, but is actually an intended feature of BIND and -can be used in this way. However, now when <CODE>www.foo.com</CODE> gets resolved, -BIND gives out <CODE>www0-www6</CODE> - but in a slightly permutated/rotated order -every time. This way the clients are spread over the various servers. - -But notice that this not a perfect load balancing scheme, because DNS resolve -information gets cached by the other nameservers on the net, so once a client -has resolved <CODE>www.foo.com</CODE> to a particular <CODE>wwwN.foo.com</CODE>, all -subsequent requests also go to this particular name <CODE>wwwN.foo.com</CODE>. But -the final result is ok, because the total sum of the requests are really -spread over the various webservers. - -<P> -<li><STRONG>DNS Load-Balancing</STRONG> - -<P> -A sophisticated DNS-based method for load-balancing is to use the program -<CODE>lbnamed</CODE> which can be found at <A -HREF="http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html">http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html</A>. -It is a Perl 5 program in conjunction with auxilliary tools which provides a -real load-balancing for DNS. - -<P> -<li><STRONG>Proxy Throughput Round-Robin</STRONG> - -<P> -In this variant we use mod_rewrite and its proxy throughput feature. First we -dedicate <CODE>www0.foo.com</CODE> to be actually <CODE>www.foo.com</CODE> by using a -single - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -www IN CNAME www0.foo.com. -</PRE></TD></TR></TABLE> - -<P> -entry in the DNS. Then we convert <CODE>www0.foo.com</CODE> to a proxy-only -server, i.e. we configure this machine so all arriving URLs are just pushed -through the internal proxy to one of the 5 other servers (<CODE>www1-www5</CODE>). -To accomplish this we first establish a ruleset which contacts a load -balancing script <CODE>lb.pl</CODE> for all URLs. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteMap lb prg:/path/to/lb.pl -RewriteRule ^/(.+)$ ${lb:$1} [P,L] -</PRE></TD></TR></TABLE> - -<P> -Then we write <CODE>lb.pl</CODE>: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -#!/path/to/perl -## -## lb.pl -- load balancing script -## - -$| = 1; - -$name = "www"; # the hostname base -$first = 1; # the first server (not 0 here, because 0 is myself) -$last = 5; # the last server in the round-robin -$domain = "foo.dom"; # the domainname - -$cnt = 0; -while (<STDIN>) { - $cnt = (($cnt+1) % ($last+1-$first)); - $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain); - print "http://$server/$_"; -} - -##EOF## -</PRE></TD></TR></TABLE> - -<P> -A last notice: Why is this useful? Seems like <CODE>www0.foo.com</CODE> still is -overloaded? The answer is yes, it is overloaded, but with plain proxy -throughput requests, only! All SSI, CGI, ePerl, etc. processing is completely -done on the other machines. This is the essential point. - -<P> -<li><STRONG>Hardware/TCP Round-Robin</STRONG> - -<P> -There is a hardware solution available, too. Cisco has a beast called -LocalDirector which does a load balancing at the TCP/IP level. Actually this -is some sort of a circuit level gateway in front of a webcluster. If you have -enough money and really need a solution with high performance, use this one. - -</ol> - -</DL> - -<P> -<H2>Reverse Proxy</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -... - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## apache-rproxy.conf -- Apache configuration for Reverse Proxy Usage -## - -# server type -ServerType standalone -Port 8000 -MinSpareServers 16 -StartServers 16 -MaxSpareServers 16 -MaxClients 16 -MaxRequestsPerChild 100 - -# server operation parameters -KeepAlive on -MaxKeepAliveRequests 100 -KeepAliveTimeout 15 -Timeout 400 -IdentityCheck off -HostnameLookups off - -# paths to runtime files -PidFile /path/to/apache-rproxy.pid -LockFile /path/to/apache-rproxy.lock -ErrorLog /path/to/apache-rproxy.elog -CustomLog /path/to/apache-rproxy.dlog "%{%v/%T}t %h -> %{SERVER}e URL: %U" - -# unused paths -ServerRoot /tmp -DocumentRoot /tmp -CacheRoot /tmp -RewriteLog /dev/null -TransferLog /dev/null -TypesConfig /dev/null -AccessConfig /dev/null -ResourceConfig /dev/null - -# speed up and secure processing -<Directory /> -Options -FollowSymLinks -SymLinksIfOwnerMatch -AllowOverwrite None -</Directory> - -# the status page for monitoring the reverse proxy -<Location /rproxy-status> -SetHandler server-status -</Location> - -# enable the URL rewriting engine -RewriteEngine on -RewriteLogLevel 0 - -# define a rewriting map with value-lists where -# mod_rewrite randomly chooses a particular value -RewriteMap server rnd:/path/to/apache-rproxy.conf-servers - -# make sure the status page is handled locally -# and make sure no one uses our proxy except ourself -RewriteRule ^/apache-rproxy-status.* - [L] -RewriteRule ^(http|ftp)://.* - [F] - -# now choose the possible servers for particular URL types -RewriteRule ^/(.*\.(cgi|shtml))$ to://${server:dynamic}/$1 [S=1] -RewriteRule ^/(.*)$ to://${server:static}/$1 - -# and delegate the generated URL by passing it -# through the proxy module -RewriteRule ^to://([^/]+)/(.*) http://$1/$2 [E=SERVER:$1,P,L] - -# and make really sure all other stuff is forbidden -# when it should survive the above rules... -RewriteRule .* - [F] - -# enable the Proxy module without caching -ProxyRequests on -NoCache * - -# setup URL reverse mapping for redirect reponses -ProxyPassReverse / http://www1.foo.dom/ -ProxyPassReverse / http://www2.foo.dom/ -ProxyPassReverse / http://www3.foo.dom/ -ProxyPassReverse / http://www4.foo.dom/ -ProxyPassReverse / http://www5.foo.dom/ -ProxyPassReverse / http://www6.foo.dom/ -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## apache-rproxy.conf-servers -- Apache/mod_rewrite selection table -## - -# list of backend servers which serve static -# pages (HTML files and Images, etc.) -static www1.foo.dom|www2.foo.dom|www3.foo.dom|www4.foo.dom - -# list of backend servers which serve dynamically -# generated page (CGI programs or mod_perl scripts) -dynamic www5.foo.dom|www6.foo.dom -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>New MIME-type, New Service</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -On the net there are a lot of nifty CGI programs. But their usage is usually -boring, so a lot of webmaster don't use them. Even Apache's Action handler -feature for MIME-types is only appropriate when the CGI programs don't need -special URLs (actually PATH_INFO and QUERY_STRINGS) as their input. - -First, let us configure a new file type with extension <CODE>.scgi</CODE> -(for secure CGI) which will be processed by the popular <CODE>cgiwrap</CODE> -program. The problem here is that for instance we use a Homogeneous URL Layout -(see above) a file inside the user homedirs has the URL -<CODE>/u/user/foo/bar.scgi</CODE>. But <CODE>cgiwrap</CODE> needs the URL in the form -<CODE>/~user/foo/bar.scgi/</CODE>. The following rule solves the problem: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^/[uge]/<STRONG>([^/]+)</STRONG>/\.www/(.+)\.scgi(.*) ... -... /internal/cgi/user/cgiwrap/~<STRONG>$1</STRONG>/$2.scgi$3 [NS,<STRONG>T=application/x-http-cgi</STRONG>] -</PRE></TD></TR></TABLE> - -<P> -Or assume we have some more nifty programs: -<CODE>wwwlog</CODE> (which displays the <CODE>access.log</CODE> for a URL subtree and -<CODE>wwwidx</CODE> (which runs Glimpse on a URL subtree). We have to -provide the URL area to these programs so they know on which area -they have to act on. But usually this ugly, because they are all the -times still requested from that areas, i.e. typically we would run -the <CODE>swwidx</CODE> program from within <CODE>/u/user/foo/</CODE> via -hyperlink to - -<P><PRE> -/internal/cgi/user/swwidx?i=/u/user/foo/ -</PRE><P> - -which is ugly. Because we have to hard-code <STRONG>both</STRONG> the location of the -area <STRONG>and</STRONG> the location of the CGI inside the hyperlink. When we have to -reorganise or area, we spend a lot of time changing the various hyperlinks. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -The solution here is to provide a special new URL format which automatically -leads to the proper CGI invocation. We configure the following: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^/([uge])/([^/]+)(/?.*)/\* /internal/cgi/user/wwwidx?i=/$1/$2$3/ -RewriteRule ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3 -</PRE></TD></TR></TABLE> - -<P> -Now the hyperlink to search at <CODE>/u/user/foo/</CODE> reads only - -<P><PRE> -HREF="*" -</PRE><P> - -which internally gets automatically transformed to - -<P><PRE> -/internal/cgi/user/wwwidx?i=/u/user/foo/ -</PRE><P> - -The same approach leads to an invocation for the access log CGI -program when the hyperlink <CODE>:log</CODE> gets used. - -</DL> - -<P> -<H2>From Static to Dynamic</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we transform a static page <CODE>foo.html</CODE> into a dynamic variant -<CODE>foo.cgi</CODE> in a seemless way, i.e. without notice by the browser/user. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We just rewrite the URL to the CGI-script and force the correct MIME-type so -it gets really run as a CGI-script. This way a request to -<CODE>/~quux/foo.html</CODE> internally leads to the invokation of -<CODE>/~quux/foo.cgi</CODE>. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^foo\.<STRONG>html</STRONG>$ foo.<STRONG>cgi</STRONG> [T=<STRONG>application/x-httpd-cgi</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>On-the-fly Content-Regeneration</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Here comes a really esoteric feature: Dynamically generated but statically -served pages, i.e. pages should be delivered as pure static pages (read from -the filesystem and just passed through), but they have to be generated -dynamically by the webserver if missing. This way you can have CGI-generated -pages which are statically served unless one (or a cronjob) removes the static -contents. Then the contents gets refreshed. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -This is done via the following ruleset: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{REQUEST_FILENAME} <STRONG>!-s</STRONG> -RewriteRule ^page\.<STRONG>html</STRONG>$ page.<STRONG>cgi</STRONG> [T=application/x-httpd-cgi,L] -</PRE></TD></TR></TABLE> - -<P> -Here a request to <CODE>page.html</CODE> leads to a internal run of a -corresponding <CODE>page.cgi</CODE> if <CODE>page.html</CODE> is still missing or has -filesize null. The trick here is that <CODE>page.cgi</CODE> is a usual CGI script -which (additionally to its STDOUT) writes its output to the file -<CODE>page.html</CODE>. Once it was run, the server sends out the data of -<CODE>page.html</CODE>. When the webmaster wants to force a refresh the contents, -he just removes <CODE>page.html</CODE> (usually done by a cronjob). - -</DL> - -<P> -<H2>Document With Autorefresh</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Wouldn't it be nice while creating a complex webpage if the webbrowser would -automatically refresh the page every time we write a new version from within -our editor? Impossible? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -No! We just combine the MIME multipart feature, the webserver NPH feature and -the URL manipulation power of mod_rewrite. First, we establish a new URL -feature: Adding just <CODE>:refresh</CODE> to any URL causes this to be refreshed -every time it gets updated on the filesystem. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1 -</PRE></TD></TR></TABLE> - -<P> -Now when we reference the URL - -<P><PRE> -/u/foo/bar/page.html:refresh -</PRE><P> - -this leads to the internal invocation of the URL - -<P><PRE> -/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html -</PRE><P> - -The only missing part is the NPH-CGI script. Although one would usually say -"left as an exercise to the reader" ;-) I will provide this, too. - -<P><PRE> -#!/sw/bin/perl -## -## nph-refresh -- NPH/CGI script for auto refreshing pages -## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved. -## -$| = 1; - -# split the QUERY_STRING variable -@pairs = split(/&/, $ENV{'QUERY_STRING'}); -foreach $pair (@pairs) { - ($name, $value) = split(/=/, $pair); - $name =~ tr/A-Z/a-z/; - $name = 'QS_' . $name; - $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg; - eval "\$$name = \"$value\""; -} -$QS_s = 1 if ($QS_s eq ''); -$QS_n = 3600 if ($QS_n eq ''); -if ($QS_f eq '') { - print "HTTP/1.0 200 OK\n"; - print "Content-type: text/html\n\n"; - print "&lt;b&gt;ERROR&lt;/b&gt;: No file given\n"; - exit(0); -} -if (! -f $QS_f) { - print "HTTP/1.0 200 OK\n"; - print "Content-type: text/html\n\n"; - print "&lt;b&gt;ERROR&lt;/b&gt;: File $QS_f not found\n"; - exit(0); -} - -sub print_http_headers_multipart_begin { - print "HTTP/1.0 200 OK\n"; - $bound = "ThisRandomString12345"; - print "Content-type: multipart/x-mixed-replace;boundary=$bound\n"; - &print_http_headers_multipart_next; -} - -sub print_http_headers_multipart_next { - print "\n--$bound\n"; -} - -sub print_http_headers_multipart_end { - print "\n--$bound--\n"; -} - -sub displayhtml { - local($buffer) = @_; - $len = length($buffer); - print "Content-type: text/html\n"; - print "Content-length: $len\n\n"; - print $buffer; -} - -sub readfile { - local($file) = @_; - local(*FP, $size, $buffer, $bytes); - ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file); - $size = sprintf("%d", $size); - open(FP, "&lt;$file"); - $bytes = sysread(FP, $buffer, $size); - close(FP); - return $buffer; -} - -$buffer = &readfile($QS_f); -&print_http_headers_multipart_begin; -&displayhtml($buffer); - -sub mystat { - local($file) = $_[0]; - local($time); - - ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file); - return $mtime; -} - -$mtimeL = &mystat($QS_f); -$mtime = $mtime; -for ($n = 0; $n &lt; $QS_n; $n++) { - while (1) { - $mtime = &mystat($QS_f); - if ($mtime ne $mtimeL) { - $mtimeL = $mtime; - sleep(2); - $buffer = &readfile($QS_f); - &print_http_headers_multipart_next; - &displayhtml($buffer); - sleep(5); - $mtimeL = &mystat($QS_f); - last; - } - sleep($QS_s); - } -} - -&print_http_headers_multipart_end; - -exit(0); - -##EOF## -</PRE> - -</DL> - -<P> -<H2>Mass Virtual Hosting</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -The <CODE><VirtualHost></CODE> feature of Apache is nice and works great -when you just have a few dozens virtual hosts. But when you are an ISP and -have hundreds of virtual hosts to provide this feature is not the best choice. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -To provide this feature we map the remote webpage or even the complete remote -webarea to our namespace by the use of the <I>Proxy Throughput</I> feature -(flag [P]): - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## vhost.map -## -www.vhost1.dom:80 /path/to/docroot/vhost1 -www.vhost2.dom:80 /path/to/docroot/vhost2 - : -www.vhostN.dom:80 /path/to/docroot/vhostN -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## httpd.conf -## - : -# use the canonical hostname on redirects, etc. -UseCanonicalName on - - : -# add the virtual host in front of the CLF-format -CustomLog /path/to/access_log "%{VHOST}e %h %l %u %t \"%r\" %>s %b" - : - -# enable the rewriting engine in the main server -RewriteEngine on - -# define two maps: one for fixing the URL and one which defines -# the available virtual hosts with their corresponding -# DocumentRoot. -RewriteMap lowercase int:tolower -RewriteMap vhost txt:/path/to/vhost.map - -# Now do the actual virtual host mapping -# via a huge and complicated single rule: -# -# 1. make sure we don't map for common locations -RewriteCond %{REQUEST_URL} !^/commonurl1/.* -RewriteCond %{REQUEST_URL} !^/commonurl2/.* - : -RewriteCond %{REQUEST_URL} !^/commonurlN/.* -# -# 2. make sure we have a Host header, because -# currently our approach only supports -# virtual hosting through this header -RewriteCond %{HTTP_HOST} !^$ -# -# 3. lowercase the hostname -RewriteCond ${lowercase:%{HTTP_HOST}|NONE} ^(.+)$ -# -# 4. lookup this hostname in vhost.map and -# remember it only when it is a path -# (and not "NONE" from above) -RewriteCond ${vhost:%1} ^(/.*)$ -# -# 5. finally we can map the URL to its docroot location -# and remember the virtual host for logging puposes -RewriteRule ^/(.*)$ %1/$1 [E=VHOST:${lowercase:%{HTTP_HOST}}] - : -</PRE></TD></TR></TABLE> - -</DL> - -<H1>Access Restriction</H1> - -<P> -<H2>Blocking of Robots</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we block a really annoying robot from retrieving pages of a specific -webarea? A <CODE>/robots.txt</CODE> file containing entries of the "Robot -Exclusion Protocol" is typically not enough to get rid of such a robot. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We use a ruleset which forbids the URLs of the webarea -<CODE>/~quux/foo/arc/</CODE> (perhaps a very deep directory indexed area where the -robot traversal would create big server load). We have to make sure that we -forbid access only to the particular robot, i.e. just forbidding the host -where the robot runs is not enough. This would block users from this host, -too. We accomplish this by also matching the User-Agent HTTP header -information. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{HTTP_USER_AGENT} ^<STRONG>NameOfBadRobot</STRONG>.* -RewriteCond %{REMOTE_ADDR} ^<STRONG>123\.45\.67\.[8-9]</STRONG>$ -RewriteRule ^<STRONG>/~quux/foo/arc/</STRONG>.+ - [<STRONG>F</STRONG>] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Blocked Inline-Images</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Assume we have under http://www.quux-corp.de/~quux/ some pages with inlined -GIF graphics. These graphics are nice, so others directly incorporate them via -hyperlinks to their pages. We don't like this practice because it adds useless -traffic to our server. - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -While we cannot 100% protect the images from inclusion, we -can at least restrict the cases where the browser sends -a HTTP Referer header. - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{HTTP_REFERER} <STRONG>!^$</STRONG> -RewriteCond %{HTTP_REFERER} !^http://www.quux-corp.de/~quux/.*$ [NC] -RewriteRule <STRONG>.*\.gif$</STRONG> - [F] -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{HTTP_REFERER} !^$ -RewriteCond %{HTTP_REFERER} !.*/foo-with-gif\.html$ -RewriteRule <STRONG>^inlined-in-foo\.gif$</STRONG> - [F] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Host Deny</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we forbid a list of externally configured hosts from using our server? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> - -For Apache >= 1.3b6: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteMap hosts-deny txt:/path/to/hosts.deny -RewriteCond ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR] -RewriteCond ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND -RewriteRule ^/.* - [F] -</PRE></TD></TR></TABLE><P> - -For Apache <= 1.3b6: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteMap hosts-deny txt:/path/to/hosts.deny -RewriteRule ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1 -RewriteRule !^NOT-FOUND/.* - [F] -RewriteRule ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1 -RewriteRule !^NOT-FOUND/.* - [F] -RewriteRule ^NOT-FOUND/(.*)$ /$1 -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## hosts.deny -## -## ATTENTION! This is a map, not a list, even when we treat it as such. -## mod_rewrite parses it for key/value pairs, so at least a -## dummy value "-" must be present for each entry. -## - -193.102.180.41 - -bsdti1.sdm.de - -192.76.162.40 - -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Proxy Deny</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we forbid a certain host or even a user of a special host from using -the Apache proxy? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We first have to make sure mod_rewrite is below(!) mod_proxy in the -<CODE>Configuration</CODE> file when compiling the Apache webserver. This way it -gets called _before_ mod_proxy. Then we configure the following for a -host-dependend deny... - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{REMOTE_HOST} <STRONG>^badhost\.mydomain\.com$</STRONG> -RewriteRule !^http://[^/.]\.mydomain.com.* - [F] -</PRE></TD></TR></TABLE> - -<P>...and this one for a user@host-dependend deny: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <STRONG>^badguy@badhost\.mydomain\.com$</STRONG> -RewriteRule !^http://[^/.]\.mydomain.com.* - [F] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Special Authentication Variant</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -Sometimes a very special authentication is needed, for instance a -authentication which checks for a set of explicitly configured users. Only -these should receive access and without explicit prompting (which would occur -when using the Basic Auth via mod_access). - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -We use a list of rewrite conditions to exclude all except our friends: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <STRONG>!^friend1@client1.quux-corp\.com$</STRONG> -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <STRONG>!^friend2</STRONG>@client2.quux-corp\.com$ -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} <STRONG>!^friend3</STRONG>@client3.quux-corp\.com$ -RewriteRule ^/~quux/only-for-friends/ - [F] -</PRE></TD></TR></TABLE> - -</DL> - -<P> -<H2>Referer-based Deflector</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -How can we program a flexible URL Deflector which acts on the "Referer" HTTP -header and can be configured with as many referring pages as we like? - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -Use the following really tricky ruleset... - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteMap deflector txt:/path/to/deflector.map - -RewriteCond %{HTTP_REFERER} !="" -RewriteCond ${deflector:%{HTTP_REFERER}} ^-$ -RewriteRule ^.* %{HTTP_REFERER} [R,L] - -RewriteCond %{HTTP_REFERER} !="" -RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND -RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L] -</PRE></TD></TR></TABLE> - -<P>... -in conjunction with a corresponding rewrite map: - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -## -## deflector.map -## - -http://www.badguys.com/bad/index.html - -http://www.badguys.com/bad/index2.html - -http://www.badguys.com/bad/index3.html http://somewhere.com/ -</PRE></TD></TR></TABLE> - -<P> -This automatically redirects the request back to the referring page (when "-" -is used as the value in the map) or to a specific URL (when an URL is -specified in the map as the second argument). - -</DL> - -<H1>Other</H1> - -<P> -<H2>External Rewriting Engine</H2> -<P> - -<DL> -<DT><STRONG>Description:</STRONG> -<DD> -A FAQ: How can we solve the FOO/BAR/QUUX/etc. problem? There seems no solution -by the use of mod_rewrite... - -<P> -<DT><STRONG>Solution:</STRONG> -<DD> -Use an external rewrite map, i.e. a program which acts like a rewrite map. It -is run once on startup of Apache receives the requested URLs on STDIN and has -to put the resulting (usually rewritten) URL on STDOUT (same order!). - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -RewriteEngine on -RewriteMap quux-map <STRONG>prg:</STRONG>/path/to/map.quux.pl -RewriteRule ^/~quux/(.*)$ /~quux/<STRONG>${quux-map:$1}</STRONG> -</PRE></TD></TR></TABLE> - -<P><TABLE BGCOLOR="#E0E5F5" BORDER="0" CELLSPACING="0" CELLPADDING="5"><TR><TD><PRE> -#!/path/to/perl - -# disable buffered I/O which would lead -# to deadloops for the Apache server -$| = 1; - -# read URLs one per line from stdin and -# generate substitution URL on stdout -while (<>) { - s|^foo/|bar/|; - print $_; -} -</PRE></TD></TR></TABLE> - -<P> -This is a demonstration-only example and just rewrites all URLs -<CODE>/~quux/foo/...</CODE> to <CODE>/~quux/bar/...</CODE>. Actually you can program -whatever you like. But notice that while such maps can be <STRONG>used</STRONG> also by -an average user, only the system administrator can <STRONG>define</STRONG> it. - -</DL> - -<!--#include virtual="footer.html" --> -</BLOCKQUOTE> -</BODY> -</HTML> |