php如何解决多线程读写同一文件
大家都知道，PHP是没有多线程概念的，尽管如此我们仍然可以用“不完美”的方法来模拟多线程。简单的说，就是队列处理。通过对文件进行加锁和解锁，来实现。当一个文件被一个用户操作时，该文件是被锁定的，其他用户只能等待，确实不够完美，但是也可以满足一些要求不高的应用。
上限判断，关键数据的写入扣钱之类
用到了Eaccelerator的内存锁和文件锁，原理：判断系统中是否安了EAccelerator如果有则使用内存锁，如果不存在，则进行文件锁。根据带入的key的不同可以实现多个锁直接的并行处理
具体类如下：file_put_contents($file, $string, LOCK_EX
<?php
/**
* CacheLock 进程锁,主要用来进行cache失效时的单进程cache获取，防止过多的SQL请求穿透到数据库
* 用于解决PHP在并发时候的锁控制,通过文件/eaccelerator进行进程间锁定
* 如果没有使用eaccelerator则进行进行文件锁处理，会做对应目录下产生对应粒度的锁
* 使用了eaccelerator则在内存中处理，性能相对较高
* 不同的锁之间并行执行，类似mysql innodb的行级锁
*
*/
class CacheLock
{
//文件锁存放路径
private $path = null;
//文件句柄
private $fp = null;
//锁粒度,设置越大粒度越小
private $hashNum = 100;
//cache key
private $name;
//是否存在eaccelerator标志
private $eAccelerator = false;
/**
* 构造函数
* 传入锁的存放路径，及cache key的名称，这样可以进行并发
* @param string $path 锁的存放目录
* @param string $name cache key
*/
public function __construct($name, $path = 'lock')
{
//判断是否存在eAccelerator,这里启用了eAccelerator之后可以进行内存锁提高效率
$this->eAccelerator = function_exists("eaccelerator_lock");
if (!$this->eAccelerator) {
if (!is_dir($path)) { //目录设置写权限
mkdir($path, 0777);
chmod($path, 0777);
}
$this->path = realpath($path) . DIRECTORY_SEPARATOR . ($this->_mycrc32($name) % $this->hashNum) . '.txt';
}
$this->name = $name;
}
/**
* crc32
* crc32封装 相同的string会算出唯一值
* @param string $string
* @return int
*/
private function _mycrc32($string)
{
$crc = abs(crc32($string));
if ($crc & 0x80000000) {
$crc ^= 0xffffffff;
$crc += 1;
}
return $crc;
}
/**
* 加锁
* Enter description here ...
*/
public function lock()
{
//如果无法开启ea内存锁，则开启文件锁
if (!$this->eAccelerator) {
//配置目录权限可写
$this->fp = fopen($this->path, 'w+');
if ($this->fp === false) {
return false;
}
return flock($this->fp, LOCK_EX);
} else {
return eaccelerator_lock($this->name);
}
}
/**
* 解锁
* Enter description here ...
*/
public function unlock()
{
if (!$this->eAccelerator) {
if ($this->fp !== false) {
flock($this->fp, LOCK_UN);
$this->deleteCache();
}
//进行关闭
fclose($this->fp);
} else {
return eaccelerator_unlock($this->name);
}
}
//删除零时文件
private function deleteCache()
{
clearstatcache(); //清除文件状态缓存
//删除1小时前的文件
$cacheDir = dirname($this->path);
$files = scandir($cacheDir);
foreach ($files as $file) {
if (strlen($file) > 2 && time() > (filemtime($cacheDir . DIRECTORY_SEPARATOR . $file) + 3600)) {
@unlink($cacheDir . DIRECTORY_SEPARATOR . $file);
}
}
}
}
?>使用如下：
$lock = new CacheLock($orderNo); //要排队访问文件要相同，即name
$lock->lock();
//logic here
$lock->unlock();asfd
<?php
/**
* LockSystem.php
*
* php锁机制
*
//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);
//释放锁
$lockSystem->releaseLock($lockKey);
*
*/
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);
}
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