Method of using locking to implement code grabbing function under concurrency based on PHP

This article is based on the PHP language and uses locking to implement the code grabbing function under concurrent conditions. The code grabbing is open during a specific period of time and does not allow the open codes to be repeated. The introduction in this article is very detailed. Friends who need it can refer to the

Requirements : Code grabbing function

Requirements:

1. Code grabbing is only open during a specific time period;

2.The codes released in each time period are limited;

3. Each code is not allowed to be repeated;

Implementation:

1. Implementation without considering concurrency:

function get_code($len){
$CHAR_ARR = array('1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','X','Y','Z','W','S','R','T');
$CHAR_ARR_LEN = count($CHAR_ARR) - 1;
$code = '';
while(--$len > 0){ $code .= $CHAR_ARR[rand(0,$CHAR_ARR_LEN)]; }
return $code;
}
$pdo = new PDO('mysql:host=localhost;dbname=ci_test','root','root');
//查询当前时间已发放验证码数量
$code_num_rs = $pdo->query("SELECT COUNT(*) as sum FROM code_test");
$code_num_arr = $code_num_rs->fetch(PDO::FETCH_ASSOC);
$code_num = $code_num_arr['sum'];
if($code_num < 1){<br>　　 sleep(2); //暂停2秒
$code = get_code(6);
var_dump( $pdo->query("INSERT INTO code_test (code,create_time) VALUES (&#39;$code&#39;,".time().")") );
}

The above code satisfies the current situation by default is the opening time, and the codes are not repeated;

Process without considering concurrency:

1) Select to query the number of verification codes issued by the current database;

2 ) If there are still places, generate a verification code, insert it into the database, and return the verification code to the client;

　3) If it is full; then return a prompt that there are no places;

2, Implemented under concurrent conditions:

Then take a look at the results obtained by the above code under concurrent conditions:

To test concurrency, you can use apache benchmark to test. apache benchmark is the performance of the HTTP SERVER under APACHE. For the evaluation tool, enter the bin directory of apche through cmd and call it through the ab command, such as: ab -c concurrent number -n total visits url

The code is as follows:

cb -c 100 -n 100 http://localhost/php_mulit.php

In this way, 100 users and colleagues compete for 1 quota. When querying, each user finds that there is still one quota, then It will generate a verification code, insert it into the database, and return the verification code; this will cause too many verification codes to be sent. In fact, after running this command, the database has 13 more records instead of one.

How to avoid this happening?

You can lock the process from judgment to insertion by adding an exclusive lock to ensure that only one process is running in this judgment process at any time. The implementation is as follows:

//生成码
function get_code($len){
$CHAR_ARR = array('1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','X','Y','Z','W','S','R','T');
$CHAR_ARR_LEN = count($CHAR_ARR) - 1;
$code = '';
while(--$len > 0){ $code .= $CHAR_ARR[rand(0,$CHAR_ARR_LEN)]; }
return $code;
}
$pdo = new PDO('mysql:host=localhost;dbname=ci_test','root','root');
$fp = fopen('lock.txt','r');
//通过排他锁 锁定该过程
if(flock($fp,LOCK_EX)){
//查询当前时间已发放验证码数量
$code_num_rs = $pdo->query("SELECT COUNT(*) as sum FROM code_test");
$code_num_arr = $code_num_rs->fetch(PDO::FETCH_ASSOC);
$code_num = $code_num_arr['sum'];
if($code_num < 1){
sleep(2);
$code = get_code(6);
var_dump( $pdo->query("INSERT INTO code_test (code,create_time) VALUES (&#39;$code&#39;,".time().")") );
}
flock($fp,LOCK_UN);
fclose($fp);
}

Lock the process through flock function.

For more flock information, please refer to the php manual: http://php.net/manual/zh/function.flock.php

Run again

The code is as follows:

cb -c 100 -n 100 http://localhost/php_mulit.php

Only one record is added to the database, ensuring that the data is correct under concurrent conditions.

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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