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MDL-43975 Sessions: Should support memcache, not just memcached

This commit adds a session handler which works using memcache (without
requiring the memcached extension), similar to the support for
memcache within MUC.

This may be less reliable than memcached but we have been using a
similar approach on our system without problems. In case, I added a
warning in config-dist.php.
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sammarshallou committed Feb 4, 2014
1 parent ad32dda commit e645b4d580d3308b73054dac6eadf1b0a0d15dfe
Showing with 254 additions and 35 deletions.
  1. +8 −0 config-dist.php
  2. +170 −0 lib/classes/session/memcache.php
  3. +1 −35 lib/classes/session/memcached.php
  4. +75 −0 lib/classes/session/util.php
@@ -240,6 +240,14 @@
// $CFG->session_memcached_acquire_lock_timeout = 120;
// $CFG->session_memcached_lock_expire = 7200; // Ignored if memcached extension <= 2.1.0
//
// Memcache session handler (requires memcached server and memcache extension):
// $CFG->session_handler_class = '\core\session\memcache';
// $CFG->session_memcache_save_path = '127.0.0.1:11211';
// $CFG->session_memcache_acquire_lock_timeout = 120;
// ** NOTE: Memcache extension has less features than memcached and may be
// less reliable. Use memcached where possible or if you encounter
// session problems. **
//
// Following setting allows you to alter how frequently is timemodified updated in sessions table.
// $CFG->session_update_timemodified_frequency = 20; // In seconds.
//
@@ -0,0 +1,170 @@
<?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/>.
/**
* Memcache based session handler.
*
* This is based on the memcached code. It lacks some features, such as
* locking options, but appears to work in practice.
*
* @package core
* @copyright 2014 The Open University
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\session;
defined('MOODLE_INTERNAL') || die();
/**
* Memcache based session handler.
*
* @package core
* @copyright 2014 The Open University
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class memcache extends handler {
/**
* Creates new instance of handler.
*/
public function __construct() {
global $CFG;
if (empty($CFG->session_memcache_save_path)) {
$this->savepath = '';
} else {
$this->savepath = $CFG->session_memcache_save_path;
}
if (empty($this->savepath)) {
$this->servers = array();
} else {
$this->servers = util::connection_string_to_memcache_servers($this->savepath);
}
if (!empty($CFG->session_memcache_acquire_lock_timeout)) {
$this->acquiretimeout = (int)$CFG->session_memcache_acquire_lock_timeout;
}
}
/**
* Starts the session.
*
* @return bool success
*/
public function start() {
$default = ini_get('max_execution_time');
set_time_limit($this->acquiretimeout);
$result = parent::start();
set_time_limit($default);
return $result;
}
/**
* Inits session handler.
*/
public function init() {
if (!extension_loaded('memcache')) {
throw new exception('sessionhandlerproblem', 'error', '', null,
'memcache extension is not loaded');
}
$version = phpversion('memcache');
if (!$version or version_compare($version, '2.2') < 0) {
throw new exception('sessionhandlerproblem', 'error', '', null,
'memcache extension version must be at least 2.2');
}
if (empty($this->savepath)) {
throw new exception('sessionhandlerproblem', 'error', '', null,
'$CFG->session_memcache_save_path must be specified in config.php');
}
ini_set('session.save_handler', 'memcache');
ini_set('session.save_path', $this->savepath);
}
/**
* Checks for existing session with given id.
*
* Note: this verifies the storage backend only, not the actual session records.
*
* @param string $sid PHP session ID
* @return bool true if session found.
*/
public function session_exists($sid) {
if (!$this->servers) {
return false;
}
$memcache = $this->get_memcache();
$value = $memcache->get($sid);
$memcache->close();
return ($value !== false);
}
/**
* Gets the memcache object with all the servers added to it.
*
* @return \Memcache Initialised memcache object
*/
protected function get_memcache() {
$memcache = new \Memcache();
foreach ($this->servers as $server) {
$memcache->addServer($server[0], $server[1]);
}
return $memcache;
}
/**
* Kills all active sessions, the core sessions table is purged afterwards.
*/
public function kill_all_sessions() {
global $DB;
if (!$this->servers) {
return;
}
$memcache = $this->get_memcache();
// Note: this can be significantly improved by fetching keys from memcache,
// 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) {
$memcache->delete($record->sid);
}
$rs->close();
$memcache->close();
}
/**
* Kills one session, the session record is removed afterwards.
*
* @param string $sid PHP session ID
*/
public function kill_session($sid) {
if (!$this->servers) {
return;
}
$memcache = $this->get_memcache();
$memcache->delete($sid);
$memcache->close();
}
}
@@ -63,7 +63,7 @@ public function __construct() {
if (empty($this->savepath)) {
$this->servers = array();
} else {
$this->servers = self::connection_string_to_servers($this->savepath);
$this->servers = util::connection_string_to_memcache_servers($this->savepath);
}
if (empty($CFG->session_memcached_prefix)) {
@@ -186,38 +186,4 @@ public function kill_session($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;
}
}
@@ -0,0 +1,75 @@
<?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/>.
/**
* Shared utility functions for session handlers.
*
* This contains functions that are shared between two or more handlers.
*
* @package core
* @copyright 2014 The Open University
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\session;
defined('MOODLE_INTERNAL') || die();
/**
* Shared utility functions for session handlers.
*
* This contains functions that are shared between two or more handlers.
*
* @package core
* @copyright 2014 The Open University
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
abstract class util {
/**
* 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 $str save_path value containing memcached connection string
* @return array
*/
public static function connection_string_to_memcache_servers($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;
}
}

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