在php中获得锁的最佳方法 [英] best way to obtain a lock in php
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问题描述
我正在尝试更新APC中的变量,并且将有许多进程尝试这样做.
I'm trying to update a variable in APC, and will be many processes trying to do that.
APC不提供锁定功能,因此我正在考虑使用其他机制...到目前为止,我发现的是mysql的GET_LOCK()和php的flock().还有什么值得考虑的吗?
APC doesn't provide locking functionality, so I'm considering using other mechanisms... what I've found so far is mysql's GET_LOCK(), and php's flock(). Anything else worth considering?
更新:我发现了sem_acquire,但这似乎是一个阻塞锁.
Update: I've found sem_acquire, but it seems to be a blocking lock.
推荐答案
/*
CLASS ExclusiveLock
Description
==================================================================
This is a pseudo implementation of mutex since php does not have
any thread synchronization objects
This class uses flock() as a base to provide locking functionality.
Lock will be released in following cases
1 - user calls unlock
2 - when this lock object gets deleted
3 - when request or script ends
==================================================================
Usage:
//get the lock
$lock = new ExclusiveLock( "mylock" );
//lock
if( $lock->lock( ) == FALSE )
error("Locking failed");
//--
//Do your work here
//--
//unlock
$lock->unlock();
===================================================================
*/
class ExclusiveLock
{
protected $key = null; //user given value
protected $file = null; //resource to lock
protected $own = FALSE; //have we locked resource
function __construct( $key )
{
$this->key = $key;
//create a new resource or get exisitng with same key
$this->file = fopen("$key.lockfile", 'w+');
}
function __destruct()
{
if( $this->own == TRUE )
$this->unlock( );
}
function lock( )
{
if( !flock($this->file, LOCK_EX | LOCK_NB))
{ //failed
$key = $this->key;
error_log("ExclusiveLock::acquire_lock FAILED to acquire lock [$key]");
return FALSE;
}
ftruncate($this->file, 0); // truncate file
//write something to just help debugging
fwrite( $this->file, "Locked\n");
fflush( $this->file );
$this->own = TRUE;
return TRUE; // success
}
function unlock( )
{
$key = $this->key;
if( $this->own == TRUE )
{
if( !flock($this->file, LOCK_UN) )
{ //failed
error_log("ExclusiveLock::lock FAILED to release lock [$key]");
return FALSE;
}
ftruncate($this->file, 0); // truncate file
//write something to just help debugging
fwrite( $this->file, "Unlocked\n");
fflush( $this->file );
$this->own = FALSE;
}
else
{
error_log("ExclusiveLock::unlock called on [$key] but its not acquired by caller");
}
return TRUE; // success
}
};
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