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
26namespace core\lock;
27
28defined('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 */
38class lock_config {
39
40    /**
41     * Get the currently configured locking subclass.
42     *
43     * @return string class name
44     * @throws \coding_exception
45     */
46    public static function get_lock_factory_class(): string {
47
48        global $CFG, $DB;
49
50        if (during_initial_install()) {
51            $lockfactoryclass = '\core\lock\installation_lock_factory';
52        } else if (isset($CFG->lock_factory) && $CFG->lock_factory != 'auto') {
53            if (!class_exists($CFG->lock_factory)) {
54                // In this case I guess it is not safe to continue. Different cluster nodes could end up using different locking
55                // types because of an installation error.
56                throw new \coding_exception('Lock factory set in $CFG does not exist: ' . $CFG->lock_factory);
57            }
58            $lockfactoryclass = $CFG->lock_factory;
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
68            // Test if the auto chosen lock factory is available.
69            $lockfactory = new $lockfactoryclass('test');
70            if (!$lockfactory->is_available()) {
71                // Final fallback - DB row locking.
72                $lockfactoryclass = '\core\lock\db_record_lock_factory';
73            }
74        }
75
76        return $lockfactoryclass;
77    }
78
79    /**
80     * Get an instance of the currently configured locking subclass.
81     *
82     * @param string $type - Unique namespace for the locks generated by this factory. e.g. core_cron
83     * @return \core\lock\lock_factory
84     * @throws \coding_exception
85     */
86    public static function get_lock_factory(string $type): \core\lock\lock_factory {
87        $lockfactoryclass = self::get_lock_factory_class();
88        $lockfactory = new $lockfactoryclass($type);
89        if (!$lockfactory->is_available()) {
90            throw new \coding_exception("Lock factory class $lockfactoryclass is not available.");
91        }
92        return $lockfactory;
93    }
94
95}
96