friendica/src/Util/Lock.php

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2017-06-04 09:26:21 +02:00
<?php
namespace Friendica\Util;
/**
* @file src/Util/Lock.php
* @brief Functions for preventing parallel execution of functions
*
*/
use dba;
use dbm;
/**
* @brief This class contain Functions for preventing parallel execution of functions
*/
class Lock {
/**
* @brief Sets a lock for a given name
*
* @param string $fn_name Name of the lock
* @param integer $timeout Seconds until we give up
* @param integer $wait_sec Time between to lock attempts
*
* @return boolean Was the lock successful?
*/
public static function set($fn_name, $timeout = 30, $wait_sec = 2) {
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if ($wait_sec == 0) {
$wait_sec = 2;
}
$got_lock = false;
$start = time();
do {
dba::lock('locks');
$lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
if (dbm::is_result($lock)) {
if ($lock['locked']) {
// When the process id isn't used anymore, we can safely claim the lock for us.
if (!posix_kill($lock['pid'], 0)) {
$lock['locked'] = false;
}
// We want to lock something that was already locked by us? So we got the lock.
if ($lock['pid'] == getmypid()) {
$got_lock = true;
}
}
if (!$lock['locked']) {
dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
$got_lock = true;
}
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} elseif (!dbm::is_result($lock)) {
dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
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$got_lock = true;
}
dba::unlock();
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if (!$got_lock) {
sleep($wait_sec);
}
} while (!$got_lock AND ((time() - $start) < $timeout));
return $got_lock;
}
/**
* @brief Removes a lock if it was set by us
*
* @param string $fn_name Name of the lock
*/
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public static function remove($fn_name) {
dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
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return;
}
}