Friendica Communications Platform (please note that this is a clone of the repository at github, issues are handled there) https://friendi.ca
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<?php
namespace Friendica\Util;
/**
* @file src/Util/Lock.php
* @brief Functions for preventing parallel execution of functions
*
*/
use Friendica\Core\Config;
use Friendica\Database\DBM;
use Memcache;
use dba;
/**
* @brief This class contain Functions for preventing parallel execution of functions
*/
class Lock {
private static $semaphore = array();
/**
* @brief Check for memcache and open a connection if configured
*
* @return object|boolean The memcache object - or "false" if not successful
*/
private static function connectMemcache() {
if (!function_exists('memcache_connect')) {
return false;
}
if (!Config::get('system', 'memcache')) {
return false;
}
$memcache_host = Config::get('system', 'memcache_host', '127.0.0.1');
$memcache_port = Config::get('system', 'memcache_port', 11211);
$memcache = new Memcache;
if (!$memcache->connect($memcache_host, $memcache_port)) {
return false;
}
return $memcache;
}
/**
* @brief Creates a semaphore key
*
* @param string $fn_name Name of the lock
*
* @return ressource the semaphore key
*/
private static function semaphoreKey($fn_name) {
$temp = get_temppath();
$file = $temp.'/'.$fn_name.'.sem';
if (!file_exists($file)) {
file_put_contents($file, $function);
}
return ftok($file, 'f');
}
/**
* @brief Sets a lock for a given name
*
* @param string $fn_name Name of the lock
* @param integer $timeout Seconds until we give up
*
* @return boolean Was the lock successful?
*/
public static function set($fn_name, $timeout = 120) {
$got_lock = false;
$start = time();
// The second parameter for "sem_acquire" doesn't exist before 5.6.1
if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
self::$semaphore[$fn_name] = sem_get(self::semaphoreKey($fn_name));
if (self::$semaphore[$fn_name]) {
return sem_acquire(self::$semaphore[$fn_name], ($timeout == 0));
}
}
$memcache = self::connectMemcache();
if (is_object($memcache)) {
$cachekey = get_app()->get_hostname().";lock:".$fn_name;
do {
// We only lock to be sure that nothing happens at exactly the same time
dba::lock('locks');
$lock = $memcache->get($cachekey);
if (!is_bool($lock)) {
$pid = (int)$lock;
// When the process id isn't used anymore, we can safely claim the lock for us.
// Or we do want to lock something that was already locked by us.
if (!posix_kill($pid, 0) || ($pid == getmypid())) {
$lock = false;
}
}
if (is_bool($lock)) {
$memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
$got_lock = true;
}
dba::unlock();
if (!$got_lock && ($timeout > 0)) {
usleep(rand(10000, 200000));
}
} while (!$got_lock && ((time() - $start) < $timeout));
return $got_lock;
}
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));
$got_lock = true;
}
} elseif (!DBM::is_result($lock)) {
dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
$got_lock = true;
}
dba::unlock();
if (!$got_lock && ($timeout > 0)) {
usleep(rand(100000, 2000000));
}
} while (!$got_lock && ((time() - $start) < $timeout));
return $got_lock;
}
/**
* @brief Removes a lock if it was set by us
*
* @param string $fn_name Name of the lock
*/
public static function remove($fn_name) {
if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
if (empty(self::$semaphore[$fn_name])) {
return false;
} else {
$success = @sem_release(self::$semaphore[$fn_name]);
unset(self::$semaphore[$fn_name]);
return $success;
}
}
$memcache = self::connectMemcache();
if (is_object($memcache)) {
$cachekey = get_app()->get_hostname().";lock:".$fn_name;
$lock = $memcache->get($cachekey);
if (!is_bool($lock)) {
if ((int)$lock == getmypid()) {
$memcache->delete($cachekey);
}
}
return;
}
dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
return;
}
/**
* @brief Removes all lock that were set by us
*/
public static function removeAll() {
$memcache = self::connectMemcache();
if (is_object($memcache)) {
// We cannot delete all cache entries, but this doesn't matter with memcache
return;
}
dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
return;
}
}