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201 lines
6.4 KiB
201 lines
6.4 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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* Flock based file locking factory.
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*
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* The file lock factory returns file locks locked with the flock function. Works OK, except on some
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* NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
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* lock will block indefinitely instead of timing out.
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*
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* @package core
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* @category lock
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* @copyright Damyon Wiese 2013
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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\lock;
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defined('MOODLE_INTERNAL') || die();
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/**
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* Flock based file locking factory.
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*
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* The file lock factory returns file locks locked with the flock function. Works OK, except on some
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* NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
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* lock will block indefinitely instead of timing out.
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*
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* @package core
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* @category lock
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* @copyright Damyon Wiese 2013
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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 file_lock_factory implements lock_factory {
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/** @var string $type - The type of lock, e.g. cache, cron, session. */
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protected $type;
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/** @var string $lockdirectory - Full system path to the directory used to store file locks. */
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protected $lockdirectory;
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/** @var boolean $verbose - If true, debugging info about the owner of the lock will be written to the lock file. */
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protected $verbose;
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/**
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* Create this lock factory.
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*
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* @param string $type - The type, e.g. cron, cache, session
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*/
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public function __construct($type) {
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global $CFG;
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$this->type = $type;
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if (!isset($CFG->file_lock_root)) {
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$this->lockdirectory = $CFG->dataroot . '/lock';
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} else {
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$this->lockdirectory = $CFG->file_lock_root;
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}
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$this->verbose = false;
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if ($CFG->debugdeveloper) {
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$this->verbose = true;
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}
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}
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/**
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* Return information about the blocking behaviour of the lock type on this platform.
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* @return boolean - False if attempting to get a lock will block indefinitely.
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*/
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public function supports_timeout() {
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global $CFG;
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return $CFG->ostype !== 'WINDOWS';
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}
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/**
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* This lock type will be automatically released when a process ends.
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* @return boolean - True
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*/
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public function supports_auto_release() {
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return true;
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}
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/**
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* Is available.
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* @return boolean - True if preventfilelocking is not set - or the file_lock_root is not in dataroot.
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*/
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public function is_available() {
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global $CFG;
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$preventfilelocking = !empty($CFG->preventfilelocking);
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$lockdirisdataroot = true;
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if (!empty($CFG->file_lock_root) && strpos($CFG->file_lock_root, $CFG->dataroot) !== 0) {
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$lockdirisdataroot = false;
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}
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return !$preventfilelocking || !$lockdirisdataroot;
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}
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/**
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* Multiple locks for the same resource cannot be held from a single process.
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* @return boolean - False
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*/
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public function supports_recursion() {
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return false;
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}
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/**
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* Get some info that might be useful for debugging.
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* @return boolean - string
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*/
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protected function get_debug_info() {
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return 'host:' . php_uname('n') . ', pid:' . getmypid() . ', time:' . time();
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}
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/**
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* Get a lock within the specified timeout or return false.
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* @param string $resource - The identifier for the lock. Should use frankenstyle prefix.
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* @param int $timeout - The number of seconds to wait for a lock before giving up.
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* @param int $maxlifetime - Unused by this lock type.
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* @return boolean - true if a lock was obtained.
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*/
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public function get_lock($resource, $timeout, $maxlifetime = 86400) {
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$giveuptime = time() + $timeout;
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$hash = md5($this->type . '_' . $resource);
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$lockdir = $this->lockdirectory . '/' . substr($hash, 0, 2);
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if (!check_dir_exists($lockdir, true, true)) {
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return false;
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}
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$lockfilename = $lockdir . '/' . $hash;
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$filehandle = fopen($lockfilename, "wb");
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// Could not open the lock file.
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if (!$filehandle) {
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return false;
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}
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do {
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// Will block on windows. So sad.
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$wouldblock = false;
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$locked = flock($filehandle, LOCK_EX | LOCK_NB, $wouldblock);
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if (!$locked && $wouldblock && $timeout > 0) {
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usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds.
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}
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// Try until the giveup time.
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} while (!$locked && $wouldblock && time() < $giveuptime);
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if (!$locked) {
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fclose($filehandle);
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return false;
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}
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if ($this->verbose) {
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fwrite($filehandle, $this->get_debug_info());
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}
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return new lock($filehandle, $this);
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}
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/**
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* Release a lock that was previously obtained with @lock.
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* @param lock $lock - A lock obtained from this factory.
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* @return boolean - true if the lock is no longer held (including if it was never held).
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*/
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public function release_lock(lock $lock) {
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$handle = $lock->get_key();
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if (!$handle) {
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// We didn't have a lock.
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return false;
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}
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$result = flock($handle, LOCK_UN);
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fclose($handle);
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return $result;
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}
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/**
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* Extend a lock that was previously obtained with @lock.
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* @param lock $lock - not used
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* @param int $maxlifetime - not used
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* @return boolean - true if the lock was extended.
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*/
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public function extend_lock(lock $lock, $maxlifetime = 86400) {
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// Not supported by this factory.
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return false;
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}
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}
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