Varnish Purge for Craft

Craft plugin for purging Varnish when elements are saved.

Installation

1. Download and extract the contents of the zip. Copy the /varnishpurge folder to your Craft plugin folder.
2. Enable the Varnish Purge plugin in Craft (Settings > Plugins).
3. Configure the plugin in your general.php config file (see "Configuration" below).
4. Let the purge commence.

Configuration

To configure Varnish Purge, create a new varnishpurge.php config file in your config folder, and override settings as needed. The following settings are the default (found in config.php in the plugin folder):

'varnishUrl' => craft()->getSiteUrl(),
'purgeEnabled' => isset($_SERVER['HTTP_X_VARNISH']),
'purgeRelated' => true,
'logAll' => 0,
'purgeUrlMap' => [],

The varnishUrl setting can also be an array if you are running a multi language site:

'varnishUrl' => array(
    'no' => 'http://your-varnish-server.com/no/',
    'en' => 'http://your-varnish-server.com/en/',
), 

####varnishUrl The url to your varnish server. Usually this is your site url, but it could be different if you don't purge through a private connection, or if you use the IP directly to bypass CloudFlare or similar services. If your site url and the varnish url is different, make sure you handle this in your VCL file.

####purgeEnabled Enables or disables the Varnish Purge plugin. You'd normally want to disable it in your dev environments and enable it in your prod environment.

####purgeRelated Enables or disables purging of related urls when an element is saved. This should normally be enabled to make sure that all relevant urls are updated, but could be disabled on high traffic websites to make sure the cache stays as warm as possible.

####logAll When set to 1 some additional logging is forced even if devMode is disabled. Useful for debugging in production environments without having to enable devMode.

####purgeUrlMap A lookup map for purging additional urls that needs it when a given url is purged.

How it works

When an element is saved, the plugin collects the urls that it thinks need to be updated, and creates a new task that sends purge requests to the Varnish server for each url.

If purgeRelated is disabled, only the url for the element itself, or the owners url if the element is a Matrix block, is purged.

If purgeRelated is enabled, the urls for all related elements are also purged. If the saved element is an entry, all directly related entry urls, all related category urls, and all urls for elements related through an entries Matrix blocks, is purged. If the saved element is an asset, all urls for elements related to that asset, either directly or through a Matrix block, is purged. And so on. The element types taken into account is entries, categories, matrix blocks and assets.

The plugin also adds a new element action to entries and categories for purging individual elements manually. When doing this, related elements are not purged, only the selected elements.

Alternatives

A good alternative to this plugin is Josh Angell's CacheMonster plugin. It takes a different approach, using the result of the {% cache %} tag to find the urls that needs to be purged, and also provides a feature to warm the cache.

This is a great solution if you're using {% cache %}, but most of the sites I'm using Varnish on is very content heavy and I've opted not to use it. When you have tens of thousands of element criterias that needs to be updated when content is updated, it's really a problem.

Setting HTTP headers in your templates

Varnish uses the HTTP headers sent by Craft to determine if/how to cache a request. You can configure this in your webserver, but I find it more flexible to do it in my templates. I usually have a config variable named addExpiryHeaders in my config, which is enabled only in production (or you'll get issues with the browser caching your pages unnecessarily), and the following code in my layout template:

{% if craft.config.addExpiryHeaders %}
    {% if expiryTime is not defined %}{% set expiryTime = '+1 day' %}{% endif %}
    
    {% set expires = now | date_modify(expiryTime) %}
    {% header "Cache-Control: max-age=" ~ (expires.timestamp - now.timestamp) %}
    {% header "Pragma: cache" %}
    {% header "Expires: " ~ expires.rfc1123() %}
    {% header "X-Remove-Cache-Control: 1" %}
{% endif %}

In your individual page templates, you can then override the expiry time of page types like this:

{% set expiryTime = '+60 mins' %}

If you want to cache static assets with Varnish, you need to set the appropriate cache headers in your webserver.

Configuring Varnish

If you plan to run a Varnish server, you really need to get your hands dirty and learn VCL. There're no shortcuts unfortunately. :) Have a look at this gist for an example VCL file. It's based on the Varnish 4.0 template made by Mattias Geniar with some adjustments for Craft.

Note: Remember to add your server ip to the purge acl

Also, read this thread on the Craft CMS StackExchange and Josh Angell's blogpost over at SuperCool.

Price, license and support

The plugin is released under the MIT license, meaning you can do what ever you want with it as long as you don't blame me. It's free, which means there is absolutely no support included, but you might get it anyway. Just post an issue here on github if you have one, and I'll see what I can do. :)