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3a3a8bb96d
Added a number of tests for the locking mechanism which can now lock arbitrary config variables. PHPBB3-9596
158 lines
3.3 KiB
PHP
158 lines
3.3 KiB
PHP
<?php
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/**
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*
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* @package phpBB3
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* @copyright (c) 2010 phpBB Group
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* @license http://opensource.org/licenses/gpl-license.php GNU Public License
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*
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*/
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/**
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* @ignore
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*/
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if (!defined('IN_PHPBB'))
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{
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exit;
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}
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/**
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* Database locking class
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* @package phpBB3
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*/
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class phpbb_lock_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 array
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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 dbal
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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 lock 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 array $config The phpBB configuration
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* @param dbal $db A database connection
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*/
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public function __construct($config_name, $config, dbal $db)
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{
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$this->config_name = $config_name;
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$this->config = $config;
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$this->db = $db;
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}
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/**
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* Tries to acquire the cron lock by updating
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* the 'cron_lock' configuration variable in the database.
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*
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* As a lock may only be held by one process at a time, lock
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* acquisition may fail if another process is holding the lock
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* or if another process obtained the lock but never released it.
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* Locks are forcibly released after a timeout of 1 hour.
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*
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* @return bool true if lock was acquired
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* false otherwise
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*/
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public function lock()
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{
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if ($this->locked)
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{
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return true;
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}
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if (!isset($this->config[$this->config_name]))
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{
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set_config($this->config_name, '0', true);
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global $config;
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$this->config = $config;
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}
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$lock_value = $this->config[$this->config_name];
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// make sure cron doesn't run multiple times in parallel
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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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$this->unique_id = time() . ' ' . unique_id();
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$sql = 'UPDATE ' . CONFIG_TABLE . "
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SET config_value = '" . $this->db->sql_escape($this->unique_id) . "'
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WHERE config_name = '" . $this->db->sql_escape($this->config_name) . "'
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AND config_value = '" . $this->db->sql_escape($lock_value) . "'";
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$this->db->sql_query($sql);
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if ($this->db->sql_affectedrows())
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{
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$this->locked = true;
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}
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else
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{
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// another cron process altered the table between script start and
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// UPDATE query so return false
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$this->locked = false;
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}
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return $this->locked;
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}
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/**
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* Releases the cron lock.
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*
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* The lock must have been previously obtained, that is, lock() call
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* was issued and returned true.
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*
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* Note: Attempting to release a cron lock that is already released,
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* that is, calling unlock() multiple times, is harmless.
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*
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* @return void
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*/
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public function unlock()
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{
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if ($this->locked)
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{
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$sql = 'UPDATE ' . CONFIG_TABLE . "
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SET config_value = '0'
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WHERE config_name = '" . $this->db->sql_escape($this->config_name) . "'
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AND config_value = '" . $this->db->sql_escape($this->unique_id) . "'";
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$this->db->sql_query($sql);
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$this->locked = false;
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}
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}
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}
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