Magento 1: Cron fatal error in app/code/core/Mage/Cron/Model/Observer.php

Question

One of my client's CRON daemon recently started sending those errors:

PHP Fatal error: Call to a member function addFieldToFilter() on a non-object in /app/code/core/Mage/Cron/Model/Observer.php on line 105

Running Magento 1.8.1.0

This corresponds to the following lines:

$this->_pendingSchedules = Mage::getModel('cron/schedule')->getCollection()
            ->addFieldToFilter('status', Mage_Cron_Model_Schedule::STATUS_PENDING)
            ->load();

I've already ensured that the Mage_Cron_Model_Resource_Schedule_Collection class exists and the file is at the right location.

I've also checked the cron_schedule table and cron is running fine, most of the scheduled job are in the success status and there's a few pending jobs as well.

I'm not quite sure where I should start debugging. Any clue where I should start looking to narrow down the issue ?

Answer 1

The code in question is:

        $this->_pendingSchedules = Mage::getModel('cron/schedule')->getCollection()
            ->addFieldToFilter('status', Mage_Cron_Model_Schedule::STATUS_PENDING)
            ->load();

Based on that, your problem is that getCollection() is not returning the object Magento expects. Is anything overriding cron/schedule, or its collection cron/resource_schedule_collection?

I would suggest adding logging in there to determine the exact type (get_class($var)) of Mage::getModel('cron/schedule') and Mage::getModel('cron/schedule')->getCollection() in that context. That should give you an idea of where to proceed. Let it run, see what comes out.

It's hard to speculate about the root cause without more info. I suspect a problem with configuration (module XML), either a file being broken, or some module overriding or replacing some XML it shouldn't.