本文实例讲述了php+redis实现的限制抢购防止商品超发功能。分享给大家供大家参考，具体如下：

redis不仅仅是单纯的缓存，它还有一些特殊的功能，在一些特殊场景上很好用。redis中key的原子自增incrby和判断key不存在再写入的setnx方法，可以有效的防止超发。

下面使用两个不同的方式来说明利用redis做商品购买库存数量限制。

业务场景很简单，就是限制抢购5个商品，模拟并发请求抢购商品，每抢购一次对应redis中的key值增加一次，通过判断限购的数量来限制抢购，抢购成功写入成功日志，失败写入失败的信息记录，通过记录的数量来判断是否超发。

文件index.php

require_once './myredis.php';

require_once './function.php';

class sendaward{

public $conf = [];

const v1 = 'way1';//版本一

const v2 = 'way2';//版本二

const amountlimit = 5;//抢购数量限制

const incramount = 1;//redis递增数量值

//初始化调用对应方法执行商品发放

public function __construct($conf,$type){

$this->conf = $conf;

if(empty($type))

return '';

if($type==self::v1){

$this->way1(self::v1);

}elseif($type==self::v2){

$this->way2(self::v2);

}else{

return '';

}

}

//抢购商品方式一

protected function way1($v){

$redis = new myredis($this->conf);

$keynmae = getkeyname($v);

if(!$redis->exists($keynmae)){

$redis->set($keynmae,0);

}

$curramount = $redis->get($keynmae);

if(($curramount+self::incramount)>self::amountlimit){

writelog("没有抢到商品",$v);

return;

}

$redis->incrby($keynmae,self::incramount);

writelog("抢到商品",$v);

}

//抢购商品方式二

protected function way2($v){

$redis = new myredis($this->conf);

$keynmae = getkeyname($v);

if(!$redis->exists($keynmae)){

$redis->setnx($keynmae,0);

}

if($redis->incrby($keynmae,self::incramount) > self::amountlimit){

writelog("没有抢到商品",$v);

return;

}

writelog("抢到商品",$v);

}

}

//实例化调用对应执行方法

$type = isset($_get['v'])?$_get['v']:'way1';

$conf = [

'host'=>'192.168.0.214','port'=>'6379',

'auth'=>'test','db'=>2,

];

new sendaward($conf,$type);

文件myredis.php

/**

* @desc 自定义redis操作类

* **/

class myredis{

public $handler = null;

public function __construct($conf){

$this->handler = new redis();

$this->handler->connect($conf['host'], $conf['port']); //连接redis

//设置密码

if(isset($conf['auth'])){

$this->handler->auth($conf['auth']); //密码验证

}

//选择数据库

if(isset($conf['db'])){

$this->handler->select($conf['db']);//选择数据库2

}else{

$this->handler->select(0);//默认选择0库

}

}

//获取key的值

public function get($name){

return $this->handler->get($name);

}

//设置key的值

public function set($name,$value){

return $this->handler->set($name,$value);

}

//判断key是否存在

public function exists($key){

if($this->handler->exists($key)){

return true;

}

return false;

}

//当key不存在的设置key的值，存在则不设置

public function setnx($key,$value){

return $this->handler->setnx($key,$value);

}

//将key的数值增加指定数值

public function incrby($key,$value){

return $this->handler->incrby($key,$value);

}

}

文件function.php

//获取商品key名称

function getkeyname($v)

{

return "send_goods_".$v;

}

//日志写入方法

function writelog($msg,$v)

{

$log = $msg.php_eol;

file_put_contents("log/$v.log",$log,file_append);

}

1.ab工具并发测试way1方法

[root@localhost oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way1

this is apachebench, version 2.3

copyright 1996 adam twiss, zeus technology ltd, http://www.zeustech.net/

licensed to the apache software foundation, http://www.apache.org/

benchmarking 192.168.0.213 (be patient)

completed 100 requests

completed 200 requests

finished 200 requests

server software: nginx

server hostname: 192.168.0.213

server port: 8083

document path: /index.php?v=way1

document length: 0 bytes

concurrency level: 100

time taken for tests: 0.089 seconds

complete requests: 200

failed requests: 0

write errors: 0

total transferred: 30600 bytes

html transferred: 0 bytes

requests per second: 2243.13 [#/sec] (mean)

time per request: 44.581 [ms] (mean)

time per request: 0.446 [ms] (mean, across all concurrent requests)

transfer rate: 335.16 [kbytes/sec] received

connection times (ms)

min mean[+/-sd] median max

connect: 0 6 2.2 5 17

processing: 2 28 16.3 25 55

waiting: 1 26 15.2 24 50

total: 5 34 16.3 30 60

percentage of the requests served within a certain time (ms)

50% 30

66% 35

75% 54

80% 56

90% 57

95% 60

98% 60

99% 60

100% 60 (longest request)

v1方法日志分析

[root@localhost log]# less -n way1.log

1 抢到商品

2 抢到商品

3 抢到商品

4 抢到商品

5 抢到商品

6 抢到商品

7 没有抢到商品

8 没有抢到商品

9 没有抢到商品

10 没有抢到商品

11 没有抢到商品

12 没有抢到商品

观察日志发现 抢到商品的记录有6条超过正常的5条，说明超发了

2.ab工具并发测试way2方法

[root@localhost oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way2

this is apachebench, version 2.3

copyright 1996 adam twiss, zeus technology ltd, http://www.zeustech.net/

licensed to the apache software foundation, http://www.apache.org/

benchmarking 192.168.0.213 (be patient)

completed 100 requests

completed 200 requests

finished 200 requests

server software: nginx

server hostname: 192.168.0.213

server port: 8083

document path: /index.php?v=way2

document length: 0 bytes

concurrency level: 100

time taken for tests: 0.087 seconds

complete requests: 200

failed requests: 0

write errors: 0

total transferred: 31059 bytes

html transferred: 0 bytes

requests per second: 2311.68 [#/sec] (mean)

time per request: 43.259 [ms] (mean)

time per request: 0.433 [ms] (mean, across all concurrent requests)

transfer rate: 350.58 [kbytes/sec] received

connection times (ms)

min mean[+/-sd] median max

connect: 0 6 5.4 5 13

processing: 3 31 16.6 30 70

waiting: 1 30 16.6 30 70

total: 5 37 18.5 32 82

percentage of the requests served within a certain time (ms)

50% 32

66% 41

75% 45

80% 50

90% 68

95% 80

98% 81

99% 82

100% 82 (longest request)

v2方法日志分析

[root@localhost log]# less -n v2.log

[root@localhost log]# less -n way2.log

1 抢到商品

2 抢到商品

3 抢到商品

4 抢到商品

5 没有抢到商品

6 抢到商品

7 没有抢到商品

8 没有抢到商品

9 没有抢到商品

10 没有抢到商品

总结：观察日志可知抢到商品的日志记录是5条并没有超发，说明利用这种方式可以限制住库存的数量。之所以超发是因为方法一中通过加法来判断限制条件的同时，并发一大，就会越过这个判断条件出现会超发，redis的在这方面就体现优势了。

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