How to operate multiple TWiki sites with a single software installation
by Ian Kluft

See my presentation slides from the Nov 29, 2007 TWiki Meetup.

It's possible to run more than one TWiki site with a single installation of the TWiki.Org software. The configuration file is usually used like a flat text file. But it's a series of Perl variable assignments. And it is itself a Perl script. It is possible to add Perl code to make the TWiki server detect the domain in which an incoming request was directed, and select configuration settings based on the incoming request.

How it started

I developed this for the Stratofox Aerospace Tracking Team in April 2004 in order to create separate private discussion web sites for the May 17 "CSXT Space Shot 2004" (in which CSXT claimed a flight altitude of 72 miles or 380,000', the first amateur rocket launch to space) and the June 7 Paragon Space Launch (which launched but experienced an in-flight failure and did not reach space). This trick was later used to set up public TWiki sites for and a public wiki for Stratofox as well.

How to do it

Note: (Nov 30, 2007) It has been pointed out that this solution works only for CGI-based TWiki environments, not on mod_perl, speedy or fastcgi. We'll have to keep working on a more general solution. But for now a solution for any environment is better than we had before.
The changes which I made to the configuration file were not extensive. This is what it took to make all those TWiki sites listed above work on one Apache HTTPD server.

This is shown in the format of a simple Unix diff. 

54a55,58
> # capture server name so this can be used for multiple TWiki's
> $ENV{SERVER_NAME} =~ /^([A-Z0-9_.-]+)/i;
> $server_name = $1;
> $server_name =~ s/^www\.//;
62c66
< $defaultUrlHost   = "http://your.domain.com";
---
> $defaultUrlHost   = "http://$server_name";
72c76
< $pubDir           = "/home/httpd/twiki/pub";
---
> $pubDir           = "/home/httpd/$server_name/twiki/pub";
76c80
< $dataDir          = "/home/httpd/twiki/data";
---
> $dataDir          = "/home/httpd/$server_name/twiki/data";
219c223
< $displayTimeValues    = "gmtime";
---
> $displayTimeValues    = "servertime";
329c333
< $wikiHomeUrl      = "http://your.domain.com/twiki";
---
> $wikiHomeUrl      = "http://$server_name/twiki";

How it works

Here's a summary of how it works.