- 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
<?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
<?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,$value);
}
}
文件function.php
<?php
//获取商品key名称
function getKeyName($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",$log,FILE_APPEND);
}
1.ab工具并发测试way1方法
[root@localhost oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way1
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.0.213 (be patient)
Completed 100 requests
Completed 200 requests
Finished 200 requests
Server Software: nginx
Server Hostname: 192.168.0.213
Server Port: 8083
Document Path: /index.php?v=way1
Document Length: 0 bytes
Concurrency Level: 100
Time taken for tests: 0.089 seconds
Complete requests: 200
Failed requests: 0
Write errors: 0
Total transferred: 30600 bytes
HTML transferred: 0 bytes
Requests per second: 2243.13 [#/sec] (mean)
Time per request: 44.581 [ms] (mean)
Time per request: 0.446 [ms] (mean, across all concurrent requests)
Transfer rate: 335.16 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 6 2.2 5 17
Processing: 2 28 16.3 25 55
Waiting: 1 26 15.2 24 50
Total: 5 34 16.3 30 60
Percentage of the requests served within a certain time (ms)
50% 30
66% 35
75% 54
80% 56
90% 57
95% 60
98% 60
99% 60
100% 60 (longest request)
v1方法日志分析
[root@localhost log]# less -N way1.log
1 抢到商品
2 抢到商品
3 抢到商品
4 抢到商品
5 抢到商品
6 抢到商品
7 没有抢到商品
8 没有抢到商品
9 没有抢到商品
10 没有抢到商品
11 没有抢到商品
12 没有抢到商品
观察日志发现 抢到商品的记录有6条超过正常的5条，说明超发了
2.ab工具并发测试way2方法
[root@localhost oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way2
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
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。