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See Release Notes
Long Term Support Release

  • Bug fixes for general core bugs in 4.1.x will end 13 November 2023 (12 months).
  • Bug fixes for security issues in 4.1.x will end 10 November 2025 (36 months).
  • PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x is supported too.
<?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/>.

/**
 * Flock based file locking factory.
 *
 * The file lock factory returns file locks locked with the flock function. Works OK, except on some
 * NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
 * lock will block indefinitely instead of timing out.
 *
 * @package    core
 * @category   lock
 * @copyright  Damyon Wiese 2013
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace core\lock;

defined('MOODLE_INTERNAL') || die();

/**
 * Flock based file locking factory.
 *
 * The file lock factory returns file locks locked with the flock function. Works OK, except on some
 * NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
 * lock will block indefinitely instead of timing out.
 *
 * @package   core
 * @category  lock
 * @copyright Damyon Wiese 2013
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class file_lock_factory implements lock_factory {

    /** @var string $type - The type of lock, e.g. cache, cron, session. */
    protected $type;

    /** @var string $lockdirectory - Full system path to the directory used to store file locks. */
    protected $lockdirectory;

    /** @var boolean $verbose - If true, debugging info about the owner of the lock will be written to the lock file. */
    protected $verbose;

    /**
     * Create this lock factory.
     *
     * @param string $type - The type, e.g. cron, cache, session
> * @param string|null $lockdirectory - Optional path to the lock directory, to override defaults.
*/
< public function __construct($type) {
> public function __construct($type, ?string $lockdirectory = null) {
global $CFG; $this->type = $type;
< if (!isset($CFG->file_lock_root)) {
> if (!is_null($lockdirectory)) { > $this->lockdirectory = $lockdirectory; > } else if (!isset($CFG->file_lock_root)) {
$this->lockdirectory = $CFG->dataroot . '/lock'; } else { $this->lockdirectory = $CFG->file_lock_root; } $this->verbose = false; if ($CFG->debugdeveloper) { $this->verbose = true; } } /** * Return information about the blocking behaviour of the lock type on this platform. * @return boolean - False if attempting to get a lock will block indefinitely. */ public function supports_timeout() { global $CFG; return $CFG->ostype !== 'WINDOWS'; } /** * This lock type will be automatically released when a process ends. * @return boolean - True */ public function supports_auto_release() { return true; } /** * Is available. * @return boolean - True if preventfilelocking is not set - or the file_lock_root is not in dataroot. */ public function is_available() { global $CFG; $preventfilelocking = !empty($CFG->preventfilelocking); $lockdirisdataroot = true;
< if (!empty($CFG->file_lock_root) && strpos($CFG->file_lock_root, $CFG->dataroot) !== 0) {
> if (strpos($this->lockdirectory, $CFG->dataroot) !== 0) {
$lockdirisdataroot = false; } return !$preventfilelocking || !$lockdirisdataroot; } /** * Multiple locks for the same resource cannot be held from a single process. * * @deprecated since Moodle 3.10. * @return boolean - False */ public function supports_recursion() { debugging('The function supports_recursion() is deprecated, please do not use it anymore.', DEBUG_DEVELOPER); return false; } /** * Get some info that might be useful for debugging. * @return boolean - string */ protected function get_debug_info() { return 'host:' . php_uname('n') . ', pid:' . getmypid() . ', time:' . time(); } /** * Get a lock within the specified timeout or return false. * @param string $resource - The identifier for the lock. Should use frankenstyle prefix. * @param int $timeout - The number of seconds to wait for a lock before giving up. * @param int $maxlifetime - Unused by this lock type. * @return boolean - true if a lock was obtained. */ public function get_lock($resource, $timeout, $maxlifetime = 86400) { $giveuptime = time() + $timeout; $hash = md5($this->type . '_' . $resource); $lockdir = $this->lockdirectory . '/' . substr($hash, 0, 2); if (!check_dir_exists($lockdir, true, true)) { return false; } $lockfilename = $lockdir . '/' . $hash; $filehandle = fopen($lockfilename, "wb"); // Could not open the lock file. if (!$filehandle) { return false; } do { // Will block on windows. So sad. $wouldblock = false; $locked = flock($filehandle, LOCK_EX | LOCK_NB, $wouldblock); if (!$locked && $wouldblock && $timeout > 0) { usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds. } // Try until the giveup time. } while (!$locked && $wouldblock && time() < $giveuptime); if (!$locked) { fclose($filehandle); return false; } if ($this->verbose) { fwrite($filehandle, $this->get_debug_info()); } return new lock($filehandle, $this); } /** * Release a lock that was previously obtained with @lock. * @param lock $lock - A lock obtained from this factory. * @return boolean - true if the lock is no longer held (including if it was never held). */ public function release_lock(lock $lock) { $handle = $lock->get_key(); if (!$handle) { // We didn't have a lock. return false; } $result = flock($handle, LOCK_UN); fclose($handle); return $result; } /** * Extend a lock that was previously obtained with @lock. * * @deprecated since Moodle 3.10. * @param lock $lock - not used * @param int $maxlifetime - not used * @return boolean - true if the lock was extended. */ public function extend_lock(lock $lock, $maxlifetime = 86400) { debugging('The function extend_lock() is deprecated, please do not use it anymore.', DEBUG_DEVELOPER); // Not supported by this factory. return false; } }