Magento – Static Block FPC Hole Punch

cachefull-page-cache

What would be the easiest way to create a FPC hole punch for static block (cms block)?

Let's say I have a static block that calls another block inside that has behaviour I want to be dynamic on every page load.

Best Answer

The easiest way I've found to holepunch CMS blocks in Magento Enterprise's Full Page Caching module has a few steps:

First, let's look at the directory structure required:

BranchLabs/CacheBuster/
    Block/Cms.php         # We inherit almost all functions from the Mage CMS
                            block, only overriding the "getCacheKeyInfo" function.
                            We do this to set the CMS block ID for later use by
                            our placeholder model.
    etc/cache.xml         # Here we target our module's version of the CMS block
                            and set their cache lifetimes to 0.
    Model/Placeholder.php # This module is responsible for freshly rendering our
                            CMS blocks every time they're requested.

With that top-down understanding in mind here's how to fill those files out.

  1. Create your own block class that extends the built in Magento CMS block. You'll need to override the "getCacheKeyInfo" function as follows too:

    <?php
// BranchLabs/CacheBuster/Block/Cms.php
class BranchLabs_CacheBuster_Block_Cms extends Mage_Cms_Block_Block {

    // Used to set the cache placeholder attribute definitions, required in
    // the placeholder's "_renderBlock" function.
    public function getCacheKeyInfo() {
        return array('block_id' => $this->getBlockId());
    }

}

  2. Set up the placeholder model that is responsible for rendering out our CMS block without applying the cache.

    <?php
// BranchLabs/CacheBuster/Model/Placeholder.php
class BranchLabs_CacheBuster_Model_Placeholder extends Enterprise_PageCache_Model_Container_Abstract {

    public function applyWithoutApp(&$content)
    {
        return false;
    }

    protected function _getCacheId()
    {
        $id = 'CACHEBUSTER_HOLEPUNCH_' . microtime() . '_' . rand(0,99);
        return $id;
    }

    /**
     * CacheBuster doesn't cache data! Do nothing.
     */
    protected function  _saveCache($data, $id, $tags = array(), $lifetime = null)
    {
        return $this;
    }

    /**
     * Render fresh block content.
     *
     * @return false|string
     */
    protected function _renderBlock()
    {
        $block = $this->_placeholder->getAttribute('block');
        $block = new $block;
        // Get the block_id attribute we originally set in our CMS block's
        // getCacheKeyInfo function.
        $block_id = $this->_placeholder->getAttribute('block_id');
        $block->setBlockId($block_id);
        $block->setLayout(Mage::app()->getLayout());
        return $block->toHtml();
    }
}

  3. Set up cache.xml to target our newly created CMS block and render using our newly created placeholder.

    <!-- BranchLabs/CacheBuster/etc/cache.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<config>
  <placeholders>
    <arbitrary_unique_identifier>
      <block>cachebuster/cms</block>
      <placeholder>ARBITRARY_UNIQUE_IDENTIFIER</placeholder>
      <container>BranchLabs_CacheBuster_Model_Placeholder</container>
      <cache_lifetime>0</cache_lifetime>
    </arbitrary_unique_identifier>
  </placeholders>
</config>

  4. In the CMS, replace the block types for the blocks you're trying render outside the cache with our newly minted CMS-proof block: {{block type="cachebuster/cms" block_id="cacheproof"}}

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