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301 lines
11 KiB
301 lines
11 KiB
2 years ago
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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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/**
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* Memcached based session handler.
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*
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* @package core
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* @copyright 2013 Petr Skoda {@link http://skodak.org}
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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namespace core\session;
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defined('MOODLE_INTERNAL') || die();
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/**
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* Memcached based session handler.
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*
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* @package core
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* @copyright 2013 Petr Skoda {@link http://skodak.org}
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class memcached extends handler {
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/** @var string $savepath save_path string */
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protected $savepath;
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/** @var array $servers list of servers parsed from save_path */
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protected $servers;
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/** @var string $prefix session key prefix */
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protected $prefix;
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/** @var int $acquiretimeout how long to wait for session lock */
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protected $acquiretimeout = 120;
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/**
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* @var int $lockexpire how long to wait before expiring the lock so that other requests
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* may continue execution, ignored if PECL memcached is below version 2.2.0.
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*/
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protected $lockexpire = 7200;
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/**
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* @var integer $lockretrysleep Used for memcached 3.x (PHP7), the amount of time to
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* sleep between attempts to acquire the session lock. Mimics the deprecated config
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* memcached.sess_lock_wait.
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*/
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protected $lockretrysleep = 150;
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/**
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* Create new instance of handler.
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*/
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public function __construct() {
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global $CFG;
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if (empty($CFG->session_memcached_save_path)) {
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$this->savepath = '';
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} else {
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$this->savepath = $CFG->session_memcached_save_path;
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}
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if (empty($this->savepath)) {
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$this->servers = array();
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} else {
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$this->servers = self::connection_string_to_memcache_servers($this->savepath);
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}
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if (empty($CFG->session_memcached_prefix)) {
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$this->prefix = ini_get('memcached.sess_prefix');
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} else {
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$this->prefix = $CFG->session_memcached_prefix;
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}
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if (!empty($CFG->session_memcached_acquire_lock_timeout)) {
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$this->acquiretimeout = (int)$CFG->session_memcached_acquire_lock_timeout;
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}
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if (!empty($CFG->session_memcached_lock_expire)) {
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$this->lockexpire = (int)$CFG->session_memcached_lock_expire;
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}
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if (!empty($CFG->session_memcached_lock_retry_sleep)) {
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$this->lockretrysleep = (int)$CFG->session_memcached_lock_retry_sleep;
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}
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}
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/**
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* Start the session.
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* @return bool success
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*/
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public function start() {
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// NOTE: memcached before 2.2.0 expires session locks automatically after max_execution_time,
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// this leads to major difference compared to other session drivers that timeout
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// and stop the second request execution instead.
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$default = ini_get('max_execution_time');
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set_time_limit($this->acquiretimeout);
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$isnewsession = empty($_COOKIE[session_name()]);
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$starttimer = microtime(true);
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$result = parent::start();
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// If session_start returned TRUE, but it took as long
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// as the timeout value, and the $_SESSION returned is
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// empty when should not have been (isnewsession false)
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// then assume it did timeout and is invalid.
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// Add 1 second to elapsed time to account for inexact
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// timings in php_memcached_session.c.
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// @TODO Remove this check when php-memcached is fixed
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// to return false after key lock acquisition timeout.
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if (!$isnewsession && $result && count($_SESSION) == 0
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&& (microtime(true) - $starttimer + 1) >= floatval($this->acquiretimeout)) {
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$result = false;
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}
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set_time_limit($default);
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return $result;
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}
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/**
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* Init session handler.
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*/
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public function init() {
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if (!extension_loaded('memcached')) {
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throw new exception('sessionhandlerproblem', 'error', '', null, 'memcached extension is not loaded');
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}
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$version = phpversion('memcached');
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if (!$version or version_compare($version, '2.0') < 0) {
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throw new exception('sessionhandlerproblem', 'error', '', null, 'memcached extension version must be at least 2.0');
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}
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if (empty($this->savepath)) {
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throw new exception('sessionhandlerproblem', 'error', '', null, '$CFG->session_memcached_save_path must be specified in config.php');
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}
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ini_set('session.save_handler', 'memcached');
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ini_set('session.save_path', $this->savepath);
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ini_set('memcached.sess_prefix', $this->prefix);
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ini_set('memcached.sess_locking', '1'); // Locking is required!
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ini_set('memcached.sess_lock_expire', $this->lockexpire);
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if (version_compare($version, '3.0.0-dev') >= 0) {
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// With memcached 3.x (PHP 7) we configure the max retries to make and the time to sleep between each retry.
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// There are two sleep config values, an initial and a max value.
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// After each attempt the memcached module adjusts the sleep value to be the lesser of the configured max
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// value, or 2X the previous value.
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// With default memcached.ini configs (5, 1s, 2s) the result is only 5 attempts to lock over 9 sec.
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// To mimic the behavior of the 2.2.x module so we get more attempts and much more frequently, config both
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// sleep values to the old default value of 150 msec (making it constant) and calculate number of retries
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// using the existing Moodle config $CFG->session_memcached_acquire_lock_timeout.
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// Doing this so admins configure session lock attempt timeout in familiar terms, and more straight-forward
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// to detect if lock attempt timeout has occurred in start().
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// If _min and _max values are not equal, the actual lock acquire timeout will not be the expected
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// configured value in $CFG->session_memcached_acquire_lock_timeout; this will cause session data loss when
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// failure to acquire the lock is not detected.
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ini_set('memcached.sess_lock_wait_min', $this->lockretrysleep);
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ini_set('memcached.sess_lock_wait_max', $this->lockretrysleep);
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ini_set('memcached.sess_lock_retries', (int)(($this->acquiretimeout * 1000) / $this->lockretrysleep) + 1);
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} else {
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// With memcached 2.2.x we configure max time to attempt lock, and accept default value (in memcached.ini)
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// for sleep time between each attempt (usually 150 msec), then memcached calculates the max number of
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// retries to make.
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ini_set('memcached.sess_lock_max_wait', $this->acquiretimeout);
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}
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}
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/**
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* Check the backend contains data for this session id.
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*
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* Note: this is intended to be called from manager::session_exists() only.
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*
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* @param string $sid
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* @return bool true if session found.
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*/
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public function session_exists($sid) {
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if (!$this->servers) {
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return false;
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}
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// Go through the list of all servers because
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// we do not know where the session handler put the
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// data.
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foreach ($this->servers as $server) {
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list($host, $port) = $server;
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$memcached = new \Memcached();
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$memcached->addServer($host, $port);
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$value = $memcached->get($this->prefix . $sid);
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$memcached->quit();
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if ($value !== false) {
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return true;
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}
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}
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return false;
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}
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/**
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* Kill all active sessions, the core sessions table is
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* purged afterwards.
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*/
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public function kill_all_sessions() {
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global $DB;
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if (!$this->servers) {
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return;
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}
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// Go through the list of all servers because
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// we do not know where the session handler put the
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// data.
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$memcacheds = array();
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foreach ($this->servers as $server) {
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list($host, $port) = $server;
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$memcached = new \Memcached();
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$memcached->addServer($host, $port);
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$memcacheds[] = $memcached;
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}
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// Note: this can be significantly improved by fetching keys from memcached,
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// but we need to make sure we are not deleting somebody else's sessions.
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$rs = $DB->get_recordset('sessions', array(), 'id DESC', 'id, sid');
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foreach ($rs as $record) {
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foreach ($memcacheds as $memcached) {
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$memcached->delete($this->prefix . $record->sid);
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}
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}
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$rs->close();
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foreach ($memcacheds as $memcached) {
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$memcached->quit();
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}
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}
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/**
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* Kill one session, the session record is removed afterwards.
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* @param string $sid
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*/
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public function kill_session($sid) {
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if (!$this->servers) {
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return;
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}
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// Go through the list of all servers because
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// we do not know where the session handler put the
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// data.
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foreach ($this->servers as $server) {
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list($host, $port) = $server;
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$memcached = new \Memcached();
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$memcached->addServer($host, $port);
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$memcached->delete($this->prefix . $sid);
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$memcached->quit();
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}
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}
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/**
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* Convert a connection string to an array of servers.
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*
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* "abc:123, xyz:789" to
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* [
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* ['abc', '123'],
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* ['xyz', '789'],
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* ]
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*
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* @param string $str save_path value containing memcached connection string
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* @return array[]
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*/
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protected static function connection_string_to_memcache_servers(string $str) : array {
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$servers = [];
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$parts = explode(',', $str);
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foreach ($parts as $part) {
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$part = trim($part);
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$pos = strrpos($part, ':');
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if ($pos !== false) {
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$host = substr($part, 0, $pos);
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$port = substr($part, ($pos + 1));
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} else {
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$host = $part;
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$port = 11211;
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}
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$servers[] = [$host, $port];
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}
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return $servers;
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}
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}
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