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Differences Between: [Versions 310 and 401] [Versions 310 and 402] [Versions 310 and 403] [Versions 39 and 310]

   1  <?php
   2  // This file is part of Moodle - http://moodle.org/
   3  //
   4  // Moodle is free software: you can redistribute it and/or modify
   5  // it under the terms of the GNU General Public License as published by
   6  // the Free Software Foundation, either version 3 of the License, or
   7  // (at your option) any later version.
   8  //
   9  // Moodle is distributed in the hope that it will be useful,
  10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  // GNU General Public License for more details.
  13  //
  14  // You should have received a copy of the GNU General Public License
  15  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16  
  17  /**
  18   * Flock based file locking factory.
  19   *
  20   * The file lock factory returns file locks locked with the flock function. Works OK, except on some
  21   * NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
  22   * lock will block indefinitely instead of timing out.
  23   *
  24   * @package    core
  25   * @category   lock
  26   * @copyright  Damyon Wiese 2013
  27   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  28   */
  29  
  30  namespace core\lock;
  31  
  32  defined('MOODLE_INTERNAL') || die();
  33  
  34  /**
  35   * Flock based file locking factory.
  36   *
  37   * The file lock factory returns file locks locked with the flock function. Works OK, except on some
  38   * NFS, exotic shared storage and exotic server OSes (like windows). On windows, a second attempt to get a
  39   * lock will block indefinitely instead of timing out.
  40   *
  41   * @package   core
  42   * @category  lock
  43   * @copyright Damyon Wiese 2013
  44   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  45   */
  46  class file_lock_factory implements lock_factory {
  47  
  48      /** @var string $type - The type of lock, e.g. cache, cron, session. */
  49      protected $type;
  50  
  51      /** @var string $lockdirectory - Full system path to the directory used to store file locks. */
  52      protected $lockdirectory;
  53  
  54      /** @var boolean $verbose - If true, debugging info about the owner of the lock will be written to the lock file. */
  55      protected $verbose;
  56  
  57      /**
  58       * Create this lock factory.
  59       *
  60       * @param string $type - The type, e.g. cron, cache, session
  61       */
  62      public function __construct($type) {
  63          global $CFG;
  64  
  65          $this->type = $type;
  66          if (!isset($CFG->file_lock_root)) {
  67              $this->lockdirectory = $CFG->dataroot . '/lock';
  68          } else {
  69              $this->lockdirectory = $CFG->file_lock_root;
  70          }
  71          $this->verbose = false;
  72          if ($CFG->debugdeveloper) {
  73              $this->verbose = true;
  74          }
  75      }
  76  
  77      /**
  78       * Return information about the blocking behaviour of the lock type on this platform.
  79       * @return boolean - False if attempting to get a lock will block indefinitely.
  80       */
  81      public function supports_timeout() {
  82          global $CFG;
  83  
  84          return $CFG->ostype !== 'WINDOWS';
  85      }
  86  
  87      /**
  88       * This lock type will be automatically released when a process ends.
  89       * @return boolean - True
  90       */
  91      public function supports_auto_release() {
  92          return true;
  93      }
  94  
  95      /**
  96       * Is available.
  97       * @return boolean - True if preventfilelocking is not set - or the file_lock_root is not in dataroot.
  98       */
  99      public function is_available() {
 100          global $CFG;
 101          $preventfilelocking = !empty($CFG->preventfilelocking);
 102          $lockdirisdataroot = true;
 103          if (!empty($CFG->file_lock_root) && strpos($CFG->file_lock_root, $CFG->dataroot) !== 0) {
 104              $lockdirisdataroot = false;
 105          }
 106          return !$preventfilelocking || !$lockdirisdataroot;
 107      }
 108  
 109      /**
 110       * Multiple locks for the same resource cannot be held from a single process.
 111       *
 112       * @deprecated since Moodle 3.10.
 113       * @return boolean - False
 114       */
 115      public function supports_recursion() {
 116          debugging('The function supports_recursion() is deprecated, please do not use it anymore.',
 117              DEBUG_DEVELOPER);
 118          return false;
 119      }
 120  
 121      /**
 122       * Get some info that might be useful for debugging.
 123       * @return boolean - string
 124       */
 125      protected function get_debug_info() {
 126          return 'host:' . php_uname('n') . ', pid:' . getmypid() . ', time:' . time();
 127      }
 128  
 129      /**
 130       * Get a lock within the specified timeout or return false.
 131       * @param string $resource - The identifier for the lock. Should use frankenstyle prefix.
 132       * @param int $timeout - The number of seconds to wait for a lock before giving up.
 133       * @param int $maxlifetime - Unused by this lock type.
 134       * @return boolean - true if a lock was obtained.
 135       */
 136      public function get_lock($resource, $timeout, $maxlifetime = 86400) {
 137          $giveuptime = time() + $timeout;
 138  
 139          $hash = md5($this->type . '_' . $resource);
 140          $lockdir = $this->lockdirectory . '/' . substr($hash, 0, 2);
 141  
 142          if (!check_dir_exists($lockdir, true, true)) {
 143              return false;
 144          }
 145  
 146          $lockfilename = $lockdir . '/' . $hash;
 147  
 148          $filehandle = fopen($lockfilename, "wb");
 149  
 150          // Could not open the lock file.
 151          if (!$filehandle) {
 152              return false;
 153          }
 154  
 155          do {
 156              // Will block on windows. So sad.
 157              $wouldblock = false;
 158              $locked = flock($filehandle, LOCK_EX | LOCK_NB, $wouldblock);
 159              if (!$locked && $wouldblock && $timeout > 0) {
 160                  usleep(rand(10000, 250000)); // Sleep between 10 and 250 milliseconds.
 161              }
 162              // Try until the giveup time.
 163          } while (!$locked && $wouldblock && time() < $giveuptime);
 164  
 165          if (!$locked) {
 166              fclose($filehandle);
 167              return false;
 168          }
 169          if ($this->verbose) {
 170              fwrite($filehandle, $this->get_debug_info());
 171          }
 172          return new lock($filehandle, $this);
 173      }
 174  
 175      /**
 176       * Release a lock that was previously obtained with @lock.
 177       * @param lock $lock - A lock obtained from this factory.
 178       * @return boolean - true if the lock is no longer held (including if it was never held).
 179       */
 180      public function release_lock(lock $lock) {
 181          $handle = $lock->get_key();
 182  
 183          if (!$handle) {
 184              // We didn't have a lock.
 185              return false;
 186          }
 187  
 188          $result = flock($handle, LOCK_UN);
 189          fclose($handle);
 190          return $result;
 191      }
 192  
 193      /**
 194       * Extend a lock that was previously obtained with @lock.
 195       *
 196       * @deprecated since Moodle 3.10.
 197       * @param lock $lock - not used
 198       * @param int $maxlifetime - not used
 199       * @return boolean - true if the lock was extended.
 200       */
 201      public function extend_lock(lock $lock, $maxlifetime = 86400) {
 202          debugging('The function extend_lock() is deprecated, please do not use it anymore.',
 203              DEBUG_DEVELOPER);
 204          // Not supported by this factory.
 205          return false;
 206      }
 207  
 208  }