Detailed explanation of steps to solve high concurrency issues using PHP file locks-PHP Tutorial-php.cn

Detailed explanation of steps to solve high concurrency issues using PHP file locks

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Release： 2023-03-26 10:18:02

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This time I will bring you a detailed explanation of the steps for PHP to use file locks to solve high concurrency. What are the precautions for PHP to use file locks to solve high concurrency? The following is a practical case, let's take a look.

Create a new .txt file without writing anything in the file.

[1]. Blocking (waiting) mode: (As long as other processes have locked the file, the current process will wait for other processes to unlock the file )

<?php
//连接数据库
$con=mysqli_connect("192.168.2.186","root","root","test");
//查询商品数量是否大于0,大于0才能下单,并减少库存
$fp = fopen("lock.txt", "r");
//加锁
if(flock($fp,LOCK_EX))
{
  $res=mysqli_fetch_assoc(mysqli_query($con,&#39;SELECT total FROM shop WHERE id=1 LIMIT 1&#39;));
  if($res[&#39;total&#39;]>0){mysqli_query($con,&#39;UPDATE shop SET total=total-1 WHERE id=1&#39;);}
  //执行完成解锁
  flock($fp,LOCK_UN);
}
//关闭文件
fclose($fp);
unset($res);
mysqli_close($con);
?>

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[2]. Non-blocking (waiting) mode:(As long as other processes have locked the file, the current process will not It will wait for other processes to unlock the file and return directly)

<?php
//连接数据库
$con=mysqli_connect("192.168.2.186","root","root","test");
//查询商品数量是否大于0,大于0才能下单,并减少库存
$fp = fopen("lock.txt", "r");
//加锁
if(flock($fp,LOCK_EX | LOCK_NB))
{
  $res=mysqli_fetch_assoc(mysqli_query($con,&#39;SELECT total FROM shop WHERE id=1 LIMIT 1&#39;));
  if($res[&#39;total&#39;]>0){mysqli_query($con,&#39;UPDATE shop SET total=total-1 WHERE id=1&#39;);}
  //执行完成解锁
  flock($fp,LOCK_UN);
}
//关闭文件
fclose($fp);
unset($res);
mysqli_close($con);
?>

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If connecting to the database takes time, there is a simple demo below for a more intuitive understanding.

demo.php

<?php
$fp = fopen("file_lock.txt", "r");
// 加锁
if(flock($fp, LOCK_EX))
{
  sleep(10);
  echo 1;
  //执行完成解锁
  flock($fp,LOCK_UN);
} else {
  echo 2;
}
//关闭文件
fclose($fp);

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demo2.php

<?php
$fp = fopen("file_lock.txt", "r");
// 加锁（如果改成flock($fp, LOCK_EX | LOCK_NB)，demo2.php会直接返回2，否则会等待demo.php执行完返回1）
if(flock($fp, LOCK_EX))
{
  echo 1;
} else {
  echo 2;
}
//关闭文件
fclose($fp);

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Run two files at the same time, and then modify the locking mechanism in demo2, you can see the blocking (waiting) mode and The difference between non-blocking (waiting) mode.

But this will cause the queue to be blocked. If 10 people write to the database at the same second, it will be blocked. The 10th person will wait for the first 9 to be executed before executing!

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!