PHP+Redis solves the practical problem of order flow limitation

1. Each issue of this series of articles will solve a practical Redis problem.
2. The questions of each issue will be selected from the comments of each issue.
3. The questions are limited to Redis related. For other questions, if I If you are interested, I don’t rule out starting a new series
4. I often use PHP, so the solution is mainly PHP
5. If there are no suitable questions in the comments, I will make up my own questions

Problem description:

This is the first issue, so I can only come up with my own questions

How to use Redis to limit the flow of orders, For example, N accesses are allowed every M seconds

Solution:

<?php

    /**
     * 是否允许放行
     * @param string $key       redis键前缀
     * @param int $timeInterval 时间间隔（秒）
     * @param int $max          时间间隔内最大放行数
     * @return bool             是否放行
     * @throws Exception
     * @example
     * <pre class="brush:php;toolbar:false">
     * //每秒放行一个
     * isAllow('my_allow');
     *
     * //每秒放行3个
     * isAllow('my_allow',1,3);
     *
     * //每3秒放行2个
     * isAllow('my_allow',3,2);
     */
    function isAllow(string $key, int $timeInterval=1, int $max=1):bool{
        if($timeInterval<1){
            throw new Exception(&#39;时间间隔必须大于0&#39;);
        }
        if($max<1){
            throw new Exception(&#39;最大放行数必须大于0&#39;);
        }

        $redis=new Redis();
        $redis->connect('192.168.31.187');
        if(!$redis->isConnected()){
            throw new Exception('Redis服务连接失败');
        }

        //对时间戳取模，使得每$timeInterval秒取得同一个时间戳
        $time=time();
        $key.=':'.($time-($time%$timeInterval));

        //自增并返回自增后的结果
        $index=$redis->incr($key);

        //如果是第一个访问，设置键的过期时间
        if($index===1){
            $redis->expire($key,$timeInterval+1);
        }

        return $index<$max+1;
    }

Code interpretation:

• Modulo the time, Make the key name updated every $timeInterval seconds

• incr() method increments the value of the key. If the key does not exist, first create a key with a value of 0 and then increment

• According to the principle of auto-increment, the value returned by the Nth auto-increment under the same key name is N

• The key name is updated every $timeInterval seconds. Therefore, the key will no longer have value

or more after the $timeInterval of creating the key for 1 second. Everyone is welcome to ask questions, correct errors, supplement, and optimize.

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