Getting ready for installation

You must have root privileges for the server on which you are installing

If you cannot get root privilges for the machine your machine you probably shouldn't be installing a load balancer on it.

Imbalance Prerequisits

• The Imbalance Archive (here)
• Database
Imbalance needs a database to work from. The name of the database can be anything you want, but, if your database already exists, the installtion procedure will destroy any existing tables named "webservers" or "function".
• MySQL User/Password
Before installation you will need a user name, a password, and a database name for Imbalance.
• A web browser (d'oh!)

imbalance-<version>/ 
	/bin
	/etc
	/docs
	/htdocs
	/phplib 

Apache Setup
Imbalance needs a webserver running PHP 4.3.0 or higher. Imbalance does not use any OOP features of which helps maintain better forward compatibility. The htdocs directory is where Imbalance expects to be located to serve imbalance.php (in most cases symbolically linked to index.php.)

In the distribution htdocs/imbalance.php is symbolicly linked index.php. If your server needs a different name, you must change the symbolic link for your server to work.

Here's a sample Apache 2 config:


<VirtualHost 192.168.0.46>
   ServerName balance
   AddType application/x-httpd-php .php
   DirectoryIndex index.html index.htm index.php
   ServerAdmin you@yoursite.com
   DocumentRoot /export/webserver/sites/balance/htdocs
   ErrorLog /export/webserver/sites/balance/logs/error.log
	<Directory>
		AllowOverride AuthConfig Indexes Limit Options
	</Directory>
<Location /server-status>
    SetHandler server-status
    Order deny,allow
    Deny from all
    Allow from 192.168.0.
    Allow from localhost
</Location>
</VirtualHost>


Note also the server-status entry. Each server that Imbalance is managing must have the server-status configured otherwise built-in apacheCost cost calculation cannot occur. If apacheCost cannot reach the server-status on a target server the target server's cost is set at 65535

Imbalance Setup
Once the webserver is set up, you can, assuming the host Imbalance is running is called imbalance, go to http://imbalance/init.php

The initial configuration page allows you to set up the basics for Imbalance. All of the fields on the page are required. When you fill in those fields and click "Submit", Imbalance will create
• <base-path>/etc/imbalance.conf
• <base-path>/etc/calccost
<base-path>/etc/calccost should be copied to your /etc/rc.d/init.d directory to load calccost at startup.

Configuration
To configure Imbalace go to http://imbalance/setup.php.
Here you can set up the hosts you wish to be managed by Imbalance.
Each host has the following attributes:
• Host: The host name of the webserver being managed.
• IP Address: The IP address of the webserver.
• Weight: An artificial cost weight to weight down slower or servers needing less hits.
• Enabled: If checked the host is enabled and will be managed by Imbalance
• Cost: The current cost value of the server being managed. This will not show up when adding hosts.
• Function: The UDF used to calculate cost
For defined hosts, the Host and Cost values are read-only. This is to prevent accidentally adding hosts, or, changing the name of hosts without proper cache management.

function %f%randomcost() {
    return rand(1,5);
}
function %proto%
{
    $url = "http://www.example.com";
    if(fopen($url) === false)
    return 65535;
    $cost = %f%randomcost();
    return $cost;
}

function simple_randomcost() {
    return rand(1,5);
}
function simple($server, $ipaddr, &$error, &$errormessage)
{
    $url = "http://www.example.com";
    if(fopen($url) === false)
    return 65535;
    $cost = simple_randomcost();
    return $cost;
}