Application of lock mechanism in PHP

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Application environment

Resolve the situation of high concurrency and negative inventory

Blocking mode

If other processes have locked the file, the current process will wait forever Continue execution after other processes unlock the file

flock($fp, LOCK_EX) //File lock

Non-blocking mode

If other processes have been added Lock the file, the current process will not wait for other processes to unlock the file, and return directly, that is, directly ignore the locking code and go to the block to close the file

flock($fp,LOCK_EX | LOCK_NB) //File lock

Code

flock($fp, LOCK_EX) and flock($fp,LOCK_EX | LOCK_NB) Replace Just click it, everything else is the same

<?php $fp = fopen(&#39;lock.txt&#39;, &#39;r&#39;);
if( flock($fp, LOCK_EX) ){      // flock($fp,LOCK_EX | LOCK_NB)
    $info = D()->query('SELECT surplus_total_num FROM tb_product WHERE id=1 LIMIT 1');
    if( $info['surplus_total_num'] > 0 ){
        D()->execute('UPDATE tb_product SET surplus_total_num = surplus_total_num - 1  WHERE id=1');
        $isSurplusProduct = 1;
    }else{
        $isSurplusProduct = 0;
    }
    flock($fp, LOCK_UN);
}
fclose($fp);

if( !$isSurplusProduct ) exit('已经没有产品了');

Concurrency test

Check whether the database inventory is consistent and remains 0 ab parameters: -c: number of concurrencies; -n: total number of requests

ab -c 20 -n 1000 http://www.test.com/test.php

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