Question

Just a simple question:

Does invalidated cache mean that caching is not running?

Answer 1

Nope, just means that it needs to be refreshed.

In Magento, whenever you make changes to products, static blocks, etc, it recognizes that the data in the database is no longer the same as what it has in the cache. Unfortunately, Magento doesn’t realize what cache data is different, just that something is different.

You will need to go into System > Cache Management and refresh the invalidated cache types.

You can set this up to automatically refresh if you like.

Create a module (or use an existing module) that you can use to set up a cron job for refreshing the cache. Create a file: {namespace}/{modulename}/Model/Observer.php

Inside that file:

<?php
class <namespace>_<modulename>_Model_Observer {

  public function refreshCache() {
    try {
      $allTypes = Mage::app()->useCache();
      foreach($allTypes as $type => $blah) {
        Mage::app()->getCacheInstance()->cleanType($type);
      }
    } catch (Exception $e) {
      // do something
      error_log($e->getMessage());
    }
  }

}

In your module’s etc/config.xml:

<config>
  ...
  <crontab>
    <jobs>
      <{modulename}_refresh_cache>
        <schedule><cron_expr>* * * * *</cron_expr></schedule>
        <run><model>{modulename}/observer::refreshCache</model></run>
      </{modulename}_refresh_cache>
    </jobs>
  </crontab>
  ...
</config>

Now as long as cron is configured correctly on your server, the cache will update automatically, as often as cron runs.