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[feature/system-cron] Abstract the database locking mechanism out of cron.

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Added a number of tests for the locking mechanism which can now lock
arbitrary config variables.

PHPBB3-9596
This commit is contained in:
Nils Adermann
2011-01-07 20:58:28 +01:00
committed by Oleg Pudeyev
parent 6e5e4721d8
commit 3a3a8bb96d
5 changed files with 243 additions and 109 deletions
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104
phpBB/includes/cron/lock.php
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@@ -1,104 +0,0 @@
<?php
/**
*
* @package phpBB3
* @copyright (c) 2010 phpBB Group
* @license http://opensource.org/licenses/gpl-license.php GNU Public License
*
*/
/**
* @ignore
*/
if (!defined('IN_PHPBB'))
{
exit;
}
/**
* Cron lock class
* @package phpBB3
*/
class phpbb_cron_lock
{
/**
* Unique identifier for this lock.
*
* @var string
*/
private $cron_id;
/**
* Tries to acquire the cron lock by updating
* the 'cron_lock' configuration variable in the database.
*
* As a lock may only be held by one process at a time, lock
* acquisition may fail if another process is holding the lock
* or if another process obtained the lock but never released it.
* Locks are forcibly released after a timeout of 1 hour.
*
* @return bool true if lock was acquired
* false otherwise
*/
public function lock()
{
global $config, $db;
if (!isset($config['cron_lock']))
{
set_config('cron_lock', '0', true);
}
// make sure cron doesn't run multiple times in parallel
if ($config['cron_lock'])
{
// if the other process is running more than an hour already we have to assume it
// aborted without cleaning the lock
$time = explode(' ', $config['cron_lock']);
$time = $time[0];
if ($time + 3600 >= time())
{
return false;
}
}
$this->cron_id = time() . ' ' . unique_id();
$sql = 'UPDATE ' . CONFIG_TABLE . "
SET config_value = '" . $db->sql_escape($this->cron_id) . "'
WHERE config_name = 'cron_lock'
AND config_value = '" . $db->sql_escape($config['cron_lock']) . "'";
$db->sql_query($sql);
// another cron process altered the table between script start and UPDATE query so exit
if ($db->sql_affectedrows() != 1)
{
return false;
}
return true;
}
/**
* Releases the cron lock.
*
* The lock must have been previously obtained, that is, lock() call
* was issued and returned true.
*
* Note: Attempting to release a cron lock that is already released,
* that is, calling unlock() multiple times, is harmless.
*
* @return void
*/
public function unlock()
{
global $db;
$sql = 'UPDATE ' . CONFIG_TABLE . "
SET config_value = '0'
WHERE config_name = 'cron_lock'
AND config_value = '" . $db->sql_escape($this->cron_id) . "'";
$db->sql_query($sql);
}
}