使用redis防止商品超發
阿新 • • 發佈：2019-01-07
- redis不僅僅是單純的快取，它還有一些特殊的功能，在一些特殊場景上很好用。redis中key的原子自增incrby和判斷key不存在再寫入的setnx方法，可以有效的防止超發。
- 下面使用兩個不同的方式來說明利用redis做商品購買庫存數量限制。
- 業務場景很簡單，就是限制搶購5個商品，模擬併發請求搶購商品，每搶購一次對應redis中的key值增加一次，通過判斷限購的數量來限制搶購，搶購成功寫入成功日誌，失敗寫入失敗的資訊記錄，通過記錄的數量來判斷是否超發。
檔案index.php
<?php require_once './myRedis.php'; require_once './function.php'; class sendAward{ public $conf = []; const V1 = 'way1';//版本一 const V2 = 'way2';//版本二 const AMOUNTLIMIT = 5;//搶購數量限制 const INCRAMOUNT = 1;//redis遞增數量值 //初始化呼叫對應方法執行商品發放 public function __construct($conf,$type){ $this->conf = $conf; if(empty($type)) return ''; if($type==self::V1){ $this->way1(self::V1); }elseif($type==self::V2){ $this->way2(self::V2); }else{ return ''; } } //搶購商品方式一 protected function way1($v){ $redis = new myRedis($this->conf); $keyNmae = getKeyName($v); if(!$redis->exists($keyNmae)){ $redis->set($keyNmae,0); } $currAmount = $redis->get($keyNmae); if(($currAmount+self::INCRAMOUNT)>self::AMOUNTLIMIT){ writeLog("沒有搶到商品",$v); return; } $redis->incrby($keyNmae,self::INCRAMOUNT); writeLog("搶到商品",$v); } //搶購商品方式二 protected function way2($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("沒有搶到商品",$v); return; } writeLog("搶到商品",$v); } } //例項化呼叫對應執行方法 $type = isset($_GET['v'])?$_GET['v']:'way1'; $conf = [ 'host'=>'192.168.0.214','port'=>'6379', 'auth'=>'test','db'=>2, ]; new sendAward($conf,$type);
檔案myRedis.php
<?php /** * @desc 自定義redis操作類 * **/ class myRedis{ public $handler = NULL; public function __construct($conf){ $this->handler = new Redis(); $this->handler->connect($conf['host'], $conf['port']); //連線Redis //設定密碼 if(isset($conf['auth'])){ $this->handler->auth($conf['auth']); //密碼驗證 } //選擇資料庫 if(isset($conf['db'])){ $this->handler->select($conf['db']);//選擇資料庫2 }else{ $this->handler->select(0);//預設選擇0庫 } } //獲取key的值 public function get($name){ return $this->handler->get($name); } //設定key的值 public function set($name,$value){ return $this->handler->set($name,$value); } //判斷key是否存在 public function exists($key){ if($this->handler->exists($key)){ return true; } return false; } //當key不存在的設定key的值，存在則不設定 public function setnx($key,$value){ return $this->handler->setnx($key,$value); } //將key的數值增加指定數值 public function incrby($key,$value){ return $this->handler->incrBy($key,$value); } }
檔案function.php
<?php
//獲取商品key名稱
function getKeyName($v)
{
return "send_goods_".$v;
}
//日誌寫入方法
function writeLog($msg,$v)
{
$log = $msg.PHP_EOL;
file_put_contents("log/$v.log",$log,FILE_APPEND);
}
1.ab工具併發測試way1方法
[[email protected] oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way1 This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking 192.168.0.213 (be patient) Completed 100 requests Completed 200 requests Finished 200 requests Server Software: nginx Server Hostname: 192.168.0.213 Server Port: 8083 Document Path: /index.php?v=way1 Document Length: 0 bytes Concurrency Level: 100 Time taken for tests: 0.089 seconds Complete requests: 200 Failed requests: 0 Write errors: 0 Total transferred: 30600 bytes HTML transferred: 0 bytes Requests per second: 2243.13 [#/sec] (mean) Time per request: 44.581 [ms] (mean) Time per request: 0.446 [ms] (mean, across all concurrent requests) Transfer rate: 335.16 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 6 2.2 5 17 Processing: 2 28 16.3 25 55 Waiting: 1 26 15.2 24 50 Total: 5 34 16.3 30 60 Percentage of the requests served within a certain time (ms) 50% 30 66% 35 75% 54 80% 56 90% 57 95% 60 98% 60 99% 60 100% 60 (longest request)
v1方法日誌分析
[[email protected] log]# less -N way1.log
1 搶到商品
2 搶到商品
3 搶到商品
4 搶到商品
5 搶到商品
6 搶到商品
7 沒有搶到商品
8 沒有搶到商品
9 沒有搶到商品
10 沒有搶到商品
11 沒有搶到商品
12 沒有搶到商品
觀察日誌發現 搶到商品的記錄有6條超過正常的5條，說明超發了
2.ab工具併發測試way2方法
[[email protected] oversend]# ab -c 100 -n 200 http://192.168.0.213:8083/index.php?v=way2
This is ApacheBench, Version 2.3 <$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方法日誌分析
[[email protected] log]# less -N v2.log
[[email protected] log]# less -N way2.log
1 搶到商品
2 搶到商品
3 搶到商品
4 搶到商品
5 沒有搶到商品
6 搶到商品
7 沒有搶到商品
8 沒有搶到商品
9 沒有搶到商品
10 沒有搶到商品總結：觀察日誌可知搶到商品的日誌記錄是5條並沒有超發，說明利用這種方式可以限制住庫存的數量。之所以超發是因為方法一中通過加法來判斷限制條件的同時，併發一大，就會越過這個判斷條件出現會超發，redis的在這方面就體現優勢了。