php并发加锁问题分析与设计代码实例讲解

<!--?php 
/** 
 * LockSystem.php 
 * 
 * php锁机制
 * 
 * Copy right (c) 2018
 * 
 * modification history: 
 * -------------------- 
 * 2018/9/10, 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);
 }
}

3 应用锁机制

3.1 支付系统应用锁

<!--?php
/** 
 * pay.php 
 * 
 * 支付应用锁
 * 
 * Copy right (c) 2018 
 * 
 * modification history: 
 * -------------------- 
 * 2018/9/10, 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);
}
?>