PmWiki / Wiki Farms
A WikiFarm is a collection of two or more wikis running on the same web server and sharing a set of common components. The term is based on the computing phrase "server farm".
This page provides some background information about WikiFarms and describes how to turn a "normal" configuration into a farm by adding a wiki. There are many ways to configure wiki farms; this page describes only one, in an effort to make it as simple as possible for the administrator who is creating a farm for the first time.
Why use a farm?
The primary motivation for using a wiki farm is to reduce the amount of administrative work involved in managing several wikis. In a farm, most of the PmWiki code is stored in one place and is shared by all the wikis. An administrator can (for example) upgrade to a new version of PmWiki on every wiki in the farm by simply updating the shared components in a single location.
From a reader's point of view, each wiki in a farm is completely independent, and appears as a separate web site. Each wiki in a farm:
Why not to use a farm
Because the wikis in a farm are all independent, it is difficult (but not impossible) to provide services that require access to more than one wiki. For example, the PmWiki search function can only search within one wiki. Using a farm as a way of subdividing related content is generally a bad idea. A much better way to subdivide content is to use WikiGroups.
I still can't decide if I need a farm ...
The good news is that you don't have to decide in advance. In fact, the recommended procedure is to first do a "normal" or single installation of PmWiki. Use it for a while. Create pages and edit them. Get to know how to add recipes. Be sure to try out WikiGroups (they may be all you need).
Once you have decided that you need another wiki, you have two basic choices:
Choice number 1 can be a good choice for several reasons:
If you choose to create a wiki farm, then read on ...
Before you create a farm, make sure that:
Creating the home wiki
You do have a working installation of PmWiki at this point, don't you? That's good, because your existing wiki is about to become the home wiki of your farm.
In the directory that contains your existing wiki, create the file local/farmconfig.php. This file is used to hold any local customizations that apply across the whole farm. For example, you could assign an admin password in farmconfig.php that will be used by all of the wikis in your farm.
If the URL used to access your existing wiki is http://www.example.com/pmwiki/ then a minimal farmconfig.php file would look like this:
<?php if (!defined('PmWiki')) exit(); $FarmPubDirUrl = 'http://www.example.com/pmwiki/pub';
This loads the variable
Amazing as it may sound, this completes all of the changes you need to make in order to turn your existing wiki into the home wiki of your farm.
Creating an additional wiki in your farm
1. Create a directory to hold the new wiki. This directory must be web-accessible, just like the directory that holds your home wiki.
2. Create a file called index.php in the directory with the following contents:
This allows your new wiki to share the PmWiki code stored in your home wiki. The
3. Open a web browser and browse the URL of the new wiki. This will be a web address starting with '
Your new wiki is now set up, and your farm now contains 2 wikis. To add more wikis, just repeat these 3 steps.
Each wiki in a farm inherits the settings stored in farmconfig.php. Do any customization that you want to apply farm-wide (to all the wikis) in farmconfig.php.
Create a local/ directory within each wiki's directory to hold local customizations that apply only to that wiki. You should at least create the local/config.php file with a new title, like so :
<?php if (!defined('PmWiki')) exit(); ## Title of your farmed wiki $WikiTitle = 'New Wiki';
Farm-wide customizations are processed before the individual wiki local customizations.
The PmWiki variable
Any Cookbook scripts you include in farmconfig.php must be included with a line such as:
Note the double quotes - single quotes may work for per farm inclusions, but they will not work for
Password use/authorization on farm wikis:
How come when I switch to another wiki within a farm, I keep my same authorization?
PmWiki uses PHP sessions to keep track of authentication/authorization information, and by default PHP sets things up such that all interactions with the same server are considered part of the same session.
An easy way to fix this is to make sure each wiki is using a different cookie name for its session identifier. Near the top of one of the wiki's local/config.php files, before calling authuser or any other recipes, add a line like:
You can pick any alphanumeric name for XYZSESSID; for example, for the cs559-1 wiki you might choose
This will keep the two wikis' sessions independent of each other.