CleverCode在工作項目中,會遇到一些php並發存取去修改一個資料問題,如果這個資料不加鎖,就會造成資料的錯誤。下面CleverCode將分析一個財務支付鎖的問題。
<?php /** * pay.php * * 支付没有应用锁 * * Copy right (c) 2016 http://blog.csdn.net/CleverCode * * modification history: * -------------------- * 2016/9/10, by CleverCode, Create * */ //用户支付 function pay($userId,$money) { if(false == is_int($userId) || false == is_int($money)) { return false; } //取出总额 $total = getUserLeftMoney($userId); //花费大于剩余 if($money > $total) { return false; } //余额 $left = $total - $money; //更新余额 return setUserLeftMoney($userId,$left); } //取出用户的余额 function getUserLeftMoney($userId) { if(false == is_int($userId)) { return 0; } $sql = "select account form user_account where userid = ${userId}"; //$mysql = new mysql();//mysql数据库 return $mysql->query($sql); } //更新用户余额 function setUserLeftMoney($userId,$money) { if(false == is_int($userId) || false == is_int($money)) { return false; } $sql = "update user_account set account = ${money} where userid = ${userId}"; //$mysql = new mysql();//mysql数据库 return $mysql->execute($sql); } ?>
#如果有兩個操作人(p和m),都用用戶編號100帳戶,分別在pc和手機端同時登陸,100帳戶總餘額有1000,p操作人花200,m操作人花300。並發過程如下。
p操作人:
1 取出使用者的餘額1000。
2 付款後剩餘 800 = 1000 - 200。
3 更新後帳戶餘額800。
m操作員:
1 取出使用者餘額1000。
2 付款後剩餘700 = 1000 - 300。
3 付款後帳戶餘額700。
兩次付款後,帳戶的餘額居然還有700,應該的情況是花費了500,帳戶餘額500才對。造成這個現象的根本原因,是並發的時候,p和m同時操作取到的餘額資料都是1000。
鎖的操作一般只有兩步,一 取得鎖(getLock);二是釋放鎖(releaseLock)。但現實鎖的方式有很多種,可以是檔案方式實作;sql實作;Memcache實作;根據這種場景我們考慮使用策略模式。
#LockSystem.php
<?php /** * LockSystem.php * * php锁机制 * * Copy right (c) 2016 http://blog.csdn.net/CleverCode * * modification history: * -------------------- * 2016/9/10, by CleverCode, Create * */ class LockSystem { const LOCK_TYPE_DB = 'SQLLock'; const LOCK_TYPE_FILE = 'FileLock'; const LOCK_TYPE_MEMCACHE = 'MemcacheLock'; private $_lock = null; private static $_supportLocks = array('FileLock', 'SQLLock', 'MemcacheLock'); public function construct($type, $options = array()) { if(false == empty($type)) { $this->createLock($type, $options); } } public function createLock($type, $options=array()) { if (false == in_array($type, self::$_supportLocks)) { throw new Exception("not support lock of ${type}"); } $this->_lock = new $type($options); } public function getLock($key, $timeout = ILock::EXPIRE) { if (false == $this->_lock instanceof ILock) { throw new Exception('false == $this->_lock instanceof ILock'); } $this->_lock->getLock($key, $timeout); } public function releaseLock($key) { if (false == $this->_lock instanceof ILock) { throw new Exception('false == $this->_lock instanceof ILock'); } $this->_lock->releaseLock($key); } } interface ILock { const EXPIRE = 5; public function getLock($key, $timeout=self::EXPIRE); public function releaseLock($key); } class FileLock implements ILock { private $_fp; private $_single; public function construct($options) { if (isset($options['path']) && is_dir($options['path'])) { $this->_lockPath = $options['path'].'/'; } else { $this->_lockPath = '/tmp/'; } $this->_single = isset($options['single'])?$options['single']:false; } public function getLock($key, $timeout=self::EXPIRE) { $startTime = Timer::getTimeStamp(); $file = md5(FILE.$key); $this->fp = fopen($this->_lockPath.$file.'.lock', "w+"); if (true || $this->_single) { $op = LOCK_EX + LOCK_NB; } else { $op = LOCK_EX; } if (false == flock($this->fp, $op, $a)) { throw new Exception('failed'); } return true; } public function releaseLock($key) { flock($this->fp, LOCK_UN); fclose($this->fp); } } class SQLLock implements ILock { public function construct($options) { $this->_db = new mysql(); } public function getLock($key, $timeout=self::EXPIRE) { $sql = "SELECT GET_LOCK('".$key."', '".$timeout."')"; $res = $this->_db->query($sql); return $res; } public function releaseLock($key) { $sql = "SELECT RELEASE_LOCK('".$key."')"; return $this->_db->query($sql); } } class MemcacheLock implements ILock { public function construct($options) { $this->memcache = new Memcache(); } public function getLock($key, $timeout=self::EXPIRE) { $waitime = 20000; $totalWaitime = 0; $time = $timeout*1000000; while ($totalWaitime < $time && false == $this->memcache->add($key, 1, $timeout)) { usleep($waitime); $totalWaitime += $waitime; } if ($totalWaitime >= $time) throw new Exception('can not get lock for waiting '.$timeout.'s.'); } public function releaseLock($key) { $this->memcache->delete($key); } }
<?php /** * pay.php * * 支付应用锁 * * Copy right (c) 2016 http://blog.csdn.net/CleverCode * * modification history: * -------------------- * 2016/9/10, by CleverCode, Create * */ //用户支付 function pay($userId,$money) { if(false == is_int($userId) || false == is_int($money)) { return false; } try { //创建锁(推荐使用MemcacheLock) $lockSystem = new LockSystem(LockSystem::LOCK_TYPE_MEMCACHE); //获取锁 $lockKey = 'pay'.$userId; $lockSystem->getLock($lockKey,8); //取出总额 $total = getUserLeftMoney($userId); //花费大于剩余 if($money > $total) { $ret = false; } else { //余额 $left = $total - $money; //更新余额 $ret = setUserLeftMoney($userId,$left); } //释放锁 $lockSystem->releaseLock($lockKey); } catch (Exception $e) { //释放锁 $lockSystem->releaseLock($lockKey); } } //取出用户的余额 function getUserLeftMoney($userId) { if(false == is_int($userId)) { return 0; } $sql = "select account form user_account where userid = ${userId}"; //$mysql = new mysql();//mysql数据库 return $mysql->query($sql); } //更新用户余额 function setUserLeftMoney($userId,$money) { if(false == is_int($userId) || false == is_int($money)) { return false; } $sql = "update user_account set account = ${money} where userid = ${userId}"; //$mysql = new mysql();//mysql数据库 return $mysql->execute($sql); } ?>
#p操作人:
1 取得鎖定:pay100
2 取出使用者的餘額1000。
3 付款後剩餘 800 = 1000 - 200。
4 更新後帳戶餘額800。
5 釋放鎖定:pay100
m 操作者:
1 等待鎖定:pay100
2 取得鎖定:pay100
2 取得鎖定:pay100
## # 取得餘額:800 4 付款後剩餘500 = 800 - 300。 5 付款後帳戶餘額500。 6 釋放鎖定:pay100#兩次付款後,餘額500。非常完美了解決了並發造成的臨界區資源的存取問題。 ###以上是php如何將並發加鎖的範例程式碼的詳細內容。更多資訊請關注PHP中文網其他相關文章!