Lagged\Session

This code already evolved into two session handlers!

Lagged\Session\SaveHandler\Memcache

This is a Memcache session handler for Zend Framework with MySQL persistence.

Each time session information is requested, it'll ask Memcached first and read from MySQL as a failover.

Data is written to Memcached and to MySQL. The write to MySQL is asynchronous (yay).

Lagged\Session\SaveHandler\Mysql

This is a Mysql session handler for Zend Framework (but without the bottlenecks Zend_Db_Table and prepared statements).

Requirements

• PHP 5.3.0+
• ext/memcache
• ext/mysqli (with mysqlnd)
• Zend Framework (tested with 1.11.11)

Setup

The setup is (hopefully) simple and straight forward. A PEAR/PECL-based solution is preferred.

PEAR & PECL

$ pecl install memcache
...
$ echo "extension=memcache.so" > /usr/local/etc/php/memcache.ini
$ pear channel-discover easybib.github.com/pear
...
$ pear install easybib/Lagged_Session_SaveHandler_Memcache-alpha
...

Note: Regarding the memcache.ini, your paths might be different, use your distributions package manager if you're not sure.

To find the location of all ini-files parsed:

$ php --ini
Configuration File (php.ini) Path: /usr/local/etc
Loaded Configuration File:         /usr/local/etc/php-cli.ini
Scan for additional .ini files in: /usr/local/etc/php
Additional .ini files parsed:      /usr/local/etc/php/apc.ini,
/usr/local/etc/php/gearman.ini,
/usr/local/etc/php/memcache.ini,
...

Manual

• compile the memcache extension and setup the memcache extension
• git clone this repository
• add path/to/repository/src' to your PHP's include_path`

Schemas

1. Memcached: But it doesn't require a schema, so we're done!
2. MySQL: The schema for MySQL can be found in var/session.sql.

Verify!

Always verify that your setup was completed correctly.

Verify the memcache extension is installed:

$ php -m|grep memcache
memcache

Verify the mysqli extension was build against mysqlnd (Client API library version):

$ php --ri mysqli

mysqli

MysqlI Support => enabled
Client API library version => mysqlnd 5.0.8-dev - 20102224 - $Revision: 310735 $
Active Persistent Links => 0
Inactive Persistent Links => 0
Active Links => 0
...

The obvious:

1. Verify Memcache is running and your application servers can access it.
2. Verify MySQL is running and all credentials are correct.

Usage

This is likely to be in one of your bootstrap files:

<?php
use Lagged\Session\Autoload as SessionAutoload;
use Lagged\Session\SaveHandler\Memcache as SessionHandler;

// yay, include_path
require_once 'Lagged/Session/Autoload.php';
SessionAutoload::register();

$memcache = new Memcache();
$memcache->addServer($config->memcache->host); // assumes default port 11211

$db = Zend_Db::factory('Mysqli', $config->database);

$saveHandler = new SessionHandler($memcache, $db);
Zend_Session::setSaveHandler($saveHandler);
register_shutdown_function('session_write_close');

To use MySQL without Memcache:

<?php
use Lagged\Session\Autoload as SessionAutoload;
use Lagged\Session\SaveHandler\Mysql as SessionHandler;

// yay, include_path
require_once 'Lagged/Session/Autoload.php';
SessionAutoload::register();

$db = Zend_Db::factory('Mysqli', $config->database);

$saveHandler = new SessionHandler($db);
Zend_Session::setSaveHandler($saveHandler);
register_shutdown_function('session_write_close');

Using Memcache without MySQL:

<?php
use Lagged\Session\Autoload as SessionAutoload;
use Lagged\Session\SaveHandler\Memcache as SessionHandler;

// yay, include_path
require_once 'Lagged/Session/Autoload.php';
SessionAutoload::register();

$memcache = new Memcache();
$memcache->addServer($config->memcache->host); // assumes default port 11211

$saveHandler = new SessionHandler($memcache);
Zend_Session::setSaveHandler($saveHandler);
register_shutdown_function('session_write_close');

Performance

It's critical to set appropriate timeouts to MySQL:

database.params.driver_options.MYSQLI_OPT_CONNECT_TIMEOUT = 5

In pure PHP:

$db->options(\MYSQLI_OPT_CONNECT_TIMEOUT, 5);

Or to \Zend_Db:

$config->database->params->driver_options = array(
    \MYSQLI_OPT_CONNECT_TIMEOUT => 5,
);

Redundancy with Memcache

To write to multiple servers, just do the following in your php.ini or memcache.ini:

memcache.redundancy=X

X being the number of nodes in your Memcache setup.

Error Handling

The code is designed to not throw Exceptions (from within the session handler) and to generally be quiet.

In case you need to debug anything in production pass $debug into __construct() and watch Syslog (it's the last parameter for either session handler). \Zend_Log with a syslog writer is used underneath.

For development and testing, you may use the following to get \RuntimeExceptions:

$saveHandler->testing = true;

Stability

So even though this code is a WIP, it's already used in production.

The versioning is conservative - whatever is publish on our PEAR channel is running in production!