This module aims to make it easy to serve up cacheable HTML pages without falling back to fully-dynamic pages as soon as the visitor takes an individualized action like adding a product to their cart. It has several cache backend models to choose from and supports dynamic block replacement via Ajax, ESI or non-Ajax Javascript. This hole-punching is only performed as-needed by using a cookie to keep track of which blocks (if any) need to be dynamic. The backends also differ in the way that cache invalidation is handled by using some interesting techniques; some of which allow for real-time cache invalidation even with a caching reverse proxy! The rendering technique allows for users with dynamic blocks to still warm the cache for other users to further increase the cache hit rate.
There are currently three backends and three hole-punching (injection) methods. Not all backends support all injection methods. The injection methods are:
- Ajax
- ESI (edge-side includes)
- Javascript (served inline with the response)
Note that all injection methods use a single injection point rather than one for every "hole".
This backend is like the Enterprise FPC except it does server-side hole punching. It does a lightweight cached response by default, and appends some javascript to inject the dynamic blocks when needed.
This backend currently uses the core Magento cache storage for it's cache storage although this will be changed to support any arbitrary cache backend.
This backend renders the response generically and uses hole-punching with Ajax or ESI as needed. Cache invalidation is handled by dumping a list of URLs to invalidate to a file and the actual invalidation of those URLs on the reverse proxy is left up to you.
This backend is like the Proxy backend in that it uses HTTP headers to signal the upstream reverse proxy to cache the response, but it uses the "must-revalidate" cache control feature of HTTP to make the reverse proxy revalidate every request. Revalidation requests are handled by a base init of Magento and are therefore very lightweight in the case of a cache hit. This makes it easy to use a caching reverse proxy upstream without explicitly invalidating large numbers of cached pages on a potentially large numbers of edge servers. Safely use a CDN for your html and still enjoy real-time invalidation! Ajax and ESI hole-punching are supported.
LAYOUT:
<reference name="top.links">
<action method="setBlockIsDynamic"></action>
</reference>
HTML:
<?php if( Mage::registry('diehard_lifetime') || ! Mage::helper('customer')->isLoggedIn() ): ?>
<p><?php echo $this->__('Welcome!') ?></p>
<?php else: ?>
<p><?php echo $this->__('Welcome back, %s!', Mage::helper('customer')->getCustomerName()) ?>
<?php endif; ?>
In the above example, the page will load with "Welcome!" and then that will be replaced by javascript with "Welcome back, Colin Mollenhour!". This logic could also be added to a block with an overridden _toHtml() method.
Alternate method:
LAYOUT:
<reference name="top.links">
<action method="setBlockIsDynamic"></action>
<action method="setSuppressOutput"><param>1</param></action>
</reference>
In the above example the top.links block will be rendered only as an empty placeholder to be filled by the hole-punching, therefore no template or block overrides are needed!
In some cases the cached version of the page will only need to be updated under certain circumstances. In this case you can add the block to a list of "ignored" blocks and remove it from the list when it needs to become dynamic again.
CONTROLLER or BLOCK prepareLayout:
if(Mage::registry('diehard'))
if($this->getSession()->getSomeVariable()) {
Mage::registry('diehard')->addIgnoredBlock($this);
} else {
Mage::registry('diehard')->removeIgnoredBlock($this);
}
}
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