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   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   * Lock configuration class, used to get an instance of the currently configured lock factory.
  19   *
  20   * @package    core
  21   * @category   lock
  22   * @copyright  Damyon Wiese 2013
  23   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24   */
  25  
  26  namespace core\lock;
  27  
  28  defined('MOODLE_INTERNAL') || die();
  29  
  30  /**
  31   * Lock configuration class, used to get an instance of the currently configured lock factory.
  32   *
  33   * @package   core
  34   * @category  lock
  35   * @copyright Damyon Wiese 2013
  36   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  37   */
  38  class lock_config {
  39  
  40      /**
  41       * Get an instance of the currently configured locking subclass.
  42       *
  43       * @param string $type - Unique namespace for the locks generated by this factory. e.g. core_cron
  44       * @return \core\lock\lock_factory
  45       * @throws \coding_exception
  46       */
  47      public static function get_lock_factory($type) {
  48          global $CFG, $DB;
  49          $lockfactory = null;
  50  
  51          if (isset($CFG->lock_factory) && $CFG->lock_factory != 'auto') {
  52              if (!class_exists($CFG->lock_factory)) {
  53                  // In this case I guess it is not safe to continue. Different cluster nodes could end up using different locking
  54                  // types because of an installation error.
  55                  throw new \coding_exception('Lock factory set in $CFG does not exist: ' . $CFG->lock_factory);
  56              }
  57              $lockfactoryclass = $CFG->lock_factory;
  58              $lockfactory = new $lockfactoryclass($type);
  59          } else {
  60              $dbtype = clean_param($DB->get_dbfamily(), PARAM_ALPHA);
  61  
  62              // DB Specific lock factory is preferred - should support auto-release.
  63              $lockfactoryclass = "\\core\\lock\\$dbtype}_lock_factory";
  64              if (!class_exists($lockfactoryclass)) {
  65                  $lockfactoryclass = '\core\lock\file_lock_factory';
  66              }
  67              /* @var lock_factory $lockfactory */
  68              $lockfactory = new $lockfactoryclass($type);
  69              if (!$lockfactory->is_available()) {
  70                  // Final fallback - DB row locking.
  71                  $lockfactory = new \core\lock\db_record_lock_factory($type);
  72              }
  73          }
  74  
  75          return $lockfactory;
  76      }
  77  
  78  }