A major part of the application I develop on my day job is a big DMS, part of which is the ability to distribute documents to staff and external parties. The distribution system works in such a way that, if sending a document to 300 people, there will actually be 300 individual emails created, rather than one email with a list of recipients. This is desired behavior. My problem is, sending 300 emails at the click of a button can take a little time, degrading the experience for the users. This portion of the call graph shows sending to just five people was taking 1+ seconds.

To solve this, I started out to implement a simple queuing system, whereby the distribution requests are added to a queue, before being sent out by a scheduled task.

Rather than refactor a lot of code and do this some fancy way, I quickly put in a solution that proved the concept and seems to work pretty well for now, with minimal effort. As an example (our code's slightly more complex, I don't get paid for nothing), here's what I started with:

< ?php
class EmailSender {
    /**
     * Takes an array of addresses and sends an email to each one.
     *
     * @param array $address
     */
    public static function sendEmails($address) {
        /**
         * Code in here
         */
    }
}

The idea was fairly simple and I'm sure it's been done many times before. First step was to rename the existing method and make it private. I then wrote a new method, that checked to see if there was a queue available, if so adds the request to the queue, otherwise calls the old method. Then all I had to do was write a method that checks the queue, running any requests it finds through the original method. We've recently adopted the Zend Framework, so checking out Zend_Queue from the incubator, reading some documentation with my docbook goggles on (couldn't be bothered to build it) and it was pretty much in place.

<?php
/**
 * Zend_Queue offline processing hack example
 *
 * @author      Dave Marshall 
 * @version     $Rev: $
 * @since       $Date: $
 * @link        $URL: $
 */
class EmailSender {

    private static $queue = null;

    /**
     * Set Queue
     *
     * @param Zend_Queue $queue
     */
    public static function setQueue($queue)
    {
        self::$queue = $queue;
    }

    /**
     * Takes an array of addresses and sends an email to each one.
     *
     * @see reallySendEmail
     * @see sendQueuedEmails
     * @param array $address
     */
    public static function sendEmail($address)
    {
        if (self::$queue === null) {
            return self::reallySendEmail($address);
        }

        self::$queue->send(serialize(func_get_args()));
    }

    /**
     * Takes an array of addresses and sends an email to each one.
     *
     * @see sendEmail
     * @param array $address
     */
    private static function reallySendEmail($address) 
    {
        /**
         * Code in here
         */
        echo 'Sending email to ' . implode(', ', $address) . PHP_EOL;
    }

    /**
     * Reads emails from the queue and sends them
     *
     * @param int $count - The number of queued items to process
     */
    public static function sendQueuedEmails($count)
    {
        /**
         * Should really check the queue is good here
         */

        $messages = self::$queue->receive(intval($count));
        foreach($messages as $msg) {
            $args = unserialize($msg->body);
            call_user_func_array(array(__CLASS__, 'reallySendEmail'), $args);
            self::$queue->deleteMessage($msg);
        }
    }
}


set_include_path(
    dirname(__FILE__) . '/src/Zend_Framework/library' . PATH_SEPARATOR
    . dirname(__FILE__) . '/src/ZendI/library' . PATH_SEPARATOR
    . get_include_path()
);

require_once "Zend/Loader.php";
Zend_Loader::registerAutoload();

define('DB_SERVER', 'localhost');
define('DB_PORT', 3306);
define('DB_USER', 'root');
define('DB_PASS', 'password');
define('DB_NAME', 'queue_example');

/**
 * Transmittal Queue
 *                   
 */
$config = array(
    'name' => 'transmittal',
    'driverOptions' => array(
        'host'     => DB_SERVER,
        'port'     => DB_PORT,
        'username' => DB_USER,
        'password' => DB_PASS,
        'dbname'   => DB_NAME,
        'type'     => 'pdo_mysql'
    )
);

// Create a database queue
$queue = new Zend_Queue('Db', $config);
$queue->createQueue('myqueue'); // called for good measure

EmailSender::setQueue($queue);

/**
 * Usage for adding to the queue
 */
EmailSender::sendEmail(array('davemastergeneral@gmail.com'));

/**
 * Usage for scheduled task
 */
EmailSender::sendQueuedEmails(5);

This may not be the best practice in the world, but it got the job done Check it out at ZFSnippets.com