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147 lines
3.2 KiB
PHP
147 lines
3.2 KiB
PHP
<?php
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/**
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*
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* This file is part of the phpBB Forum Software package.
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*
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* @copyright (c) phpBB Limited <https://www.phpbb.com>
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* @license GNU General Public License, version 2 (GPL-2.0)
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*
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* For full copyright and license information, please see
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* the docs/CREDITS.txt file.
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*
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*/
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namespace phpbb\lock;
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/**
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* Database locking class
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*/
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class db
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{
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/**
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* Name of the config variable this lock uses
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* @var string
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*/
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private $config_name;
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/**
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* Unique identifier for this lock.
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*
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* @var string
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*/
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private $unique_id;
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/**
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* Stores the state of this lock
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* @var bool
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*/
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private $locked;
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/**
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* The phpBB configuration
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* @var \phpbb\config\config
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*/
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private $config;
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/**
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* A database connection
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* @var \phpbb\db\driver\driver_interface
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*/
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private $db;
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/**
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* Creates a named released instance of the lock.
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*
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* You have to call acquire() to actually create the lock.
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*
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* @param string $config_name A config variable to be used for locking
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* @param \phpbb\config\config $config The phpBB configuration
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* @param \phpbb\db\driver\driver_interface $db A database connection
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*/
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public function __construct($config_name, \phpbb\config\config $config, \phpbb\db\driver\driver_interface $db)
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{
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$this->config_name = $config_name;
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$this->config = $config;
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$this->db = $db;
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}
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/**
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* Tries to acquire the lock by updating
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* the configuration variable in the database.
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*
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* As a lock may only be held by one process at a time, lock
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* acquisition may fail if another process is holding the lock
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* or if another process obtained the lock but never released it.
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* Locks are forcibly released after a timeout of 1 hour.
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*
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* @return bool true if lock was acquired
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* false otherwise
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*/
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public function acquire()
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{
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if ($this->locked)
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{
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return false;
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}
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if (!isset($this->config[$this->config_name]))
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{
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$this->config->set($this->config_name, '0', false);
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}
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$lock_value = $this->config[$this->config_name];
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// make sure lock cannot be acquired by multiple processes
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if ($lock_value)
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{
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// if the other process is running more than an hour already we have to assume it
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// aborted without cleaning the lock
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$time = explode(' ', $lock_value);
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$time = $time[0];
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if ($time + 3600 >= time())
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{
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return false;
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}
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}
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$this->unique_id = time() . ' ' . unique_id();
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// try to update the config value, if it was already modified by another
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// process we failed to acquire the lock.
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$this->locked = $this->config->set_atomic($this->config_name, $lock_value, $this->unique_id, false);
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return $this->locked;
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}
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/**
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* Does this process own the lock?
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*
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* @return bool true if lock is owned
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* false otherwise
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*/
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public function owns_lock()
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{
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return (bool) $this->locked;
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}
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/**
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* Releases the lock.
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*
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* The lock must have been previously obtained, that is, acquire() call
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* was issued and returned true.
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*
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* Note: Attempting to release a lock that is already released,
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* that is, calling release() multiple times, is harmless.
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*
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* @return null
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*/
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public function release()
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{
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if ($this->locked)
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{
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$this->config->set_atomic($this->config_name, $this->unique_id, '0', false);
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$this->locked = false;
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}
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}
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}
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