Codeigniter cron job from CLI throws memcached errors

Question

I'm trying to set up the cron jobs for my Codigniter application, however when I run the cron, it throws me memcached errors:

PHP Fatal error: Call to a member function get() on a non-object in /var/www/domain.com/www/dev/system/libraries/Cache/drivers/Cache_memcached.php on line 50

Fatal error: Call to a member function get() on a non-object in /var/www/domain.com/www/dev/system/libraries/Cache/drivers/Cache_memcached.php on line 50

Although I have no idea why this is throwing all the time, I can't find any errors in my cron job file, nor how to solve this problem because I don't know where this is being called, I looked into my autoloaded libraries and helpers, none of them seem to be wrong.

I also can confirm that memcached is installed, if I visit my site, memcached indeed works.

I tried suppressing the get() in Cached_memcached.php with a @, but this didn't help because no output is shown (but there is supposed to be output shown).

The command I run for the cron (user: www-data) is:

/usr/bin/php -q /var/www/domain.com/www/dev/index.php cron run cron 

I'm running Ubuntu 11.10 x86_64.

This is my cron file:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Cron extends CI_Controller {

    var $current_cron_tasks = array('cron');

    public function run($mode)
    {
        if($this->input->is_cli_request())
        {
            if(isset($mode) || !empty($mode))
            {
                if(in_array($mode, $this->current_cron_tasks))
                {
                    $this->benchmark->mark('cron_start');

                    if($mode == 'cron')
                    {
                        if($this->cache->memcached->get('currency_cache'))
                        {
                            if($this->cache->memcached->delete('currency_cache'))
                            {
                                $this->load->library('convert');
                                $this->convert->get_cache(true);
                            }
                        }

                        echo $mode . ' executed successfully';  
                    }

                    $this->benchmark->mark('cron_end');
                    $elapsed_time = $this->benchmark->elapsed_time('cron_start', 'cron_end');

                    echo $elapsed_time;
                }
            }
        }
    }   
}

Answer 1

The first thing to try would be the following to determine if memcached is supported.

var_dump($this->cache->memcached->is_supported());

The second thing to ensure is that you've got a memcached.php file in application/config/

It should contain a multidimensional array of memcached hosts with the following keys:

• host
• port
• weight

The following example defines two servers. The array keys server_1 and server_2 are irrelevant, they can be named however.

$config = array(
    'server_1' => array(
        'host'      => '127.0.0.1',
        'port'      => 11211,
        'weight'    => 1
    ),
    'server_2' => array(
        'host'      => '127.0.0.2',
        'port'      => 11211,
        'weight'    => 1
    )
);

The next thing I'd try is check to see if the controller can be run in the web browser as opposed to the CLI or if you get the same error.

Also, explicitly loading the memcached driver might be worthwhile trying. The following will load the memcached driver, and failing that call upon the file cache driver.

$this->load->driver('cache', array('adapter' => 'memcached', 'backup' => 'file'));

Using this method allows you to call $this->cache->get(); to take into account the fallback too.

Another thing to check is that you're not using separate php.ini files for web and CLI.

On Ubuntu it's located in

/etc/php5/cli/php.ini

And you should ensure that the following line is present, and not commented out

extension=memcache.so

Alternatively, you can create a file /etc/php5/cond.d/memcache.ini with the same contents.

Don't forget to restart services after changing configuration files.

You can check memcached is indeed set up correctly using the CLI by executing the following

php -i | grep memcache

Answer 2

The problem is that $this->cache->memcached is NULL (or otherwise uninitialized), meaning that the cache hasn't been initialized.

An easy fix would be to simply create the memcache object yourself. The proper fix, however, would be to look through the source and trace how the memcache object normally gets instantiated (look for new Memcache and set a debug_print_backtrace() there. Trace the debug stack back and compare it with what your cron does - look where it goes wrong then correct it). This is basic debugging btw, sorry.

Also, make sure you do load the drivers. If your cron uses a different bootstrap function than your normal index (never used CI, is that even possible?) then make sure that the memcache init is placed in the right location.

-edit-

$this->cache->memcached probably isn't actually NULL, but the actual connection to the Memcache server definitely wasn't made before you started calling get().