Issue #1260888 by joshk: Added Update README to reference varnish-cache.org...

for your site much faster and at higher volumes than Apache,

in the neighborhood of 3000 requests per second.

## What does it do?

The main function of the varnish.module is to dynamically expire/purge items

from the Varnish cache when things change in Drupal. Future innovations may

allow dynamic adjustment of the VCL (varnish configuration), but for now the

purpose is to clear the external cache on demand.

## Installation

In order to install the module you need to do the following:

First of all, you need to have Varnish installed on your server. For more

information on how to do this, please see:

http://www.varnish-cache.org/

Once you have Varnish working, use the module you need to do the following:

* Enable the module.

* Add something like this to your settings.php file:

// Add Varnish as the page cache handler.

$conf['cache_backends'] = array('sites/all/modules/varnish/varnish.cache.inc');

$conf['cache_class_cache_page'] = 'VarnishCache';

  // Drupal 7 does not cache pages when we invoke hooks during bootstrap. This needs

  // to be disabled.

// Drupal 7 does not cache pages when we invoke hooks during bootstrap.

// This needs to be disabled.

$conf['page_cache_invoke_hooks'] = FALSE;

* Go to admin/config/development/varnish and configure your connection Varnish

  appropriately. It should be pretty straight forward from here on.

## Running the simpletests for Varnish

In order to test the Varnish module, you need a "working" Varnish configuration that caches

pages for anonymous users. You also need to specify the variables that configures

your Varnish connection in your $conf array in your settings.php file.

 No newline at end of file

In order to test the Varnish module, you need a "working" Varnish

configuration that caches pages for anonymous users. You also need to specify

the variables that configures your Varnish connection in your $conf array in

your settings.php file.

## Troubleshooting

Please note that Varnish version 3 automatically configures a random key to

protect access to the control terminal, which the module needs to use. You

will either need to get the key from the secret key file (/etc/varnish/secret

in Ubuntu), or adjust your Varnish configuration not to use a key.

Debugging Varnish itself is beyond the scope of this module, but you can also

see if Varnish is functioning correctly with this site:

http://www.isvarnishworking.com/

There are also a number of resources available from the Varnish community:

http://www.varnish-cache.org/