Verzeichnisstruktur phpBB-3.1.0
- Veröffentlicht
- 27.10.2014
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db.php
001 <?php
002 /**
003 *
004 * This file is part of the phpBB Forum Software package.
005 *
006 * @copyright (c) phpBB Limited <https://www.phpbb.com>
007 * @license GNU General Public License, version 2 (GPL-2.0)
008 *
009 * For full copyright and license information, please see
010 * the docs/CREDITS.txt file.
011 *
012 */
013
014 namespace phpbb\lock;
015
016 /**
017 * Database locking class
018 */
019 class db
020 {
021 /**
022 * Name of the config variable this lock uses
023 * @var string
024 */
025 private $config_name;
026
027 /**
028 * Unique identifier for this lock.
029 *
030 * @var string
031 */
032 private $unique_id;
033
034 /**
035 * Stores the state of this lock
036 * @var bool
037 */
038 private $locked;
039
040 /**
041 * The phpBB configuration
042 * @var \phpbb\config\config
043 */
044 private $config;
045
046 /**
047 * A database connection
048 * @var \phpbb\db\driver\driver_interface
049 */
050 private $db;
051
052 /**
053 * Creates a named released instance of the lock.
054 *
055 * You have to call acquire() to actually create the lock.
056 *
057 * @param string $config_name A config variable to be used for locking
058 * @param \phpbb\config\config $config The phpBB configuration
059 * @param \phpbb\db\driver\driver_interface $db A database connection
060 */
061 public function __construct($config_name, \phpbb\config\config $config, \phpbb\db\driver\driver_interface $db)
062 {
063 $this->config_name = $config_name;
064 $this->config = $config;
065 $this->db = $db;
066 }
067
068 /**
069 * Tries to acquire the lock by updating
070 * the configuration variable in the database.
071 *
072 * As a lock may only be held by one process at a time, lock
073 * acquisition may fail if another process is holding the lock
074 * or if another process obtained the lock but never released it.
075 * Locks are forcibly released after a timeout of 1 hour.
076 *
077 * @return bool true if lock was acquired
078 * false otherwise
079 */
080 public function acquire()
081 {
082 if ($this->locked)
083 {
084 return false;
085 }
086
087 if (!isset($this->config[$this->config_name]))
088 {
089 $this->config->set($this->config_name, '0', false);
090 }
091 $lock_value = $this->config[$this->config_name];
092
093 // make sure lock cannot be acquired by multiple processes
094 if ($lock_value)
095 {
096 // if the other process is running more than an hour already we have to assume it
097 // aborted without cleaning the lock
098 $time = explode(' ', $lock_value);
099 $time = $time[0];
100
101 if ($time + 3600 >= time())
102 {
103 return false;
104 }
105 }
106
107 $this->unique_id = time() . ' ' . unique_id();
108
109 // try to update the config value, if it was already modified by another
110 // process we failed to acquire the lock.
111 $this->locked = $this->config->set_atomic($this->config_name, $lock_value, $this->unique_id, false);
112
113 return $this->locked;
114 }
115
116 /**
117 * Does this process own the lock?
118 *
119 * @return bool true if lock is owned
120 * false otherwise
121 */
122 public function owns_lock()
123 {
124 return (bool) $this->locked;
125 }
126
127 /**
128 * Releases the lock.
129 *
130 * The lock must have been previously obtained, that is, acquire() call
131 * was issued and returned true.
132 *
133 * Note: Attempting to release a lock that is already released,
134 * that is, calling release() multiple times, is harmless.
135 *
136 * @return null
137 */
138 public function release()
139 {
140 if ($this->locked)
141 {
142 $this->config->set_atomic($this->config_name, $this->unique_id, '0', false);
143 $this->locked = false;
144 }
145 }
146 }
147