Files
moodle/lib/classes/session/memcached.php
Petr Škoda 6ec361c6bc MDL-42485 add session lock acquire timeout to memcached session driver
Credit goes to Eric Merrill, thanks!
2013-10-27 16:05:12 +01:00

224 lines
7.0 KiB
PHP

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Memcached based session handler.
*
* @package core
* @copyright 2013 Petr Skoda {@link http://skodak.org}
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\session;
defined('MOODLE_INTERNAL') || die();
/**
* Memcached based session handler.
*
* @package core
* @copyright 2013 Petr Skoda {@link http://skodak.org}
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class memcached extends handler {
/** @var string $savepath save_path string */
protected $savepath;
/** @var array $servers list of servers parsed from save_path */
protected $servers;
/** @var string $prefix session key prefix */
protected $prefix;
/** @var int $acquiretimeout how long to wait for session lock */
protected $acquiretimeout = 120;
/**
* @var int $lockexpire how long to wait before expiring the lock so that other requests
* may continue execution, ignored if memcached <= 2.1.0.
*/
protected $lockexpire = 7200;
/**
* Create new instance of handler.
*/
public function __construct() {
global $CFG;
if (empty($CFG->session_memcached_save_path)) {
$this->savepath = '';
} else {
$this->savepath = $CFG->session_memcached_save_path;
}
if (empty($this->savepath)) {
$this->servers = array();
} else {
$this->servers = self::connection_string_to_servers($this->savepath);
}
if (empty($CFG->session_memcached_prefix)) {
$this->prefix = ini_get('memcached.sess_prefix');
} else {
$this->prefix = $CFG->session_memcached_prefix;
}
if (!empty($CFG->session_memcached_acquire_lock_timeout)) {
$this->acquiretimeout = (int)$CFG->session_memcached_acquire_lock_timeout;
}
if (!empty($CFG->session_memcached_lock_expire)) {
$this->lockexpire = (int)$CFG->session_memcached_lock_expire;
}
}
/**
* Start the session.
* @return bool success
*/
public function start() {
// NOTE: memcached <= 2.1.0 expires session locks automatically after max_execution_time,
// this leads to major difference compared to other session drivers that timeout
// and stop the second request execution instead.
$default = ini_get('max_execution_time');
set_time_limit($this->acquiretimeout);
$result = parent::start();
set_time_limit($default);
return $result;
}
/**
* Init session handler.
*/
public function init() {
if (!extension_loaded('memcached')) {
throw new exception('sessionhandlerproblem', 'error', '', null, 'memcached extension is not loaded');
}
$version = phpversion('memcached');
if (!$version or version_compare($version, '2.0') < 0) {
throw new exception('sessionhandlerproblem', 'error', '', null, 'memcached extension version must be at least 2.0');
}
if (empty($this->savepath)) {
throw new exception('sessionhandlerproblem', 'error', '', null, '$CFG->session_memcached_save_path must be specified in config.php');
}
ini_set('session.save_handler', 'memcached');
ini_set('session.save_path', $this->savepath);
ini_set('memcached.sess_prefix', $this->prefix);
ini_set('memcached.sess_locking', '1'); // Locking is required!
// Try to configure lock and expire timeouts - ignored if memcached <=2.1.0.
ini_set('memcached.sess_lock_max_wait', $this->acquiretimeout);
ini_set('memcached.sess_lock_expire', $this->lockexpire);
}
/**
* Check for existing session with id $sid.
*
* Note: this verifies the storage backend only, not the actual session records.
*
* @param string $sid
* @return bool true if session found.
*/
public function session_exists($sid) {
if (!$this->servers) {
return false;
}
$memcached = new \Memcached();
$memcached->addServers($this->servers);
$value = $memcached->get($this->prefix.$sid);
$memcached->quit();
return ($value !== false);
}
/**
* Kill all active sessions, the core sessions table is
* purged afterwards.
*/
public function kill_all_sessions() {
global $DB;
if (!$this->servers) {
return;
}
$memcached = new \Memcached();
$memcached->addServers($this->servers);
// Note: this can be significantly improved by fetching keys from memcached,
// but we need to make sure we are not deleting somebody else's sessions.
$rs = $DB->get_recordset('sessions', array(), 'id DESC', 'id, sid');
foreach ($rs as $record) {
$memcached->delete($this->prefix.$record->sid);
}
$rs->close();
$memcached->quit();
}
/**
* Kill one session, the session record is removed afterwards.
* @param string $sid
*/
public function kill_session($sid) {
if (!$this->servers) {
return;
}
$memcached = new \Memcached();
$memcached->addServers($this->servers);
$memcached->delete($this->prefix.$sid);
$memcached->quit();
}
/**
* Convert a connection string to an array of servers
*
* EG: Converts: "abc:123, xyz:789" to
*
* array(
* array('abc', '123'),
* array('xyz', '789'),
* )
*
* @copyright 2013 Moodlerooms Inc. (http://www.moodlerooms.com)
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
* @author Mark Nielsen
*
* @param string $str save_path value containing memcached connection string
* @return array
*/
protected static function connection_string_to_servers($str) {
$servers = array();
$parts = explode(',', $str);
foreach ($parts as $part) {
$part = trim($part);
$pos = strrpos($part, ':');
if ($pos !== false) {
$host = substr($part, 0, $pos);
$port = substr($part, ($pos + 1));
} else {
$host = $part;
$port = 11211;
}
$servers[] = array($host, $port);
}
return $servers;
}
}