1.我的環境是windows下的phpstudy,進入到apache/bin目錄裏面有個ab.exe,壓力測試命令如下
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./ab.exe -c 200 -n 1000 http://192.168.1.244/mysql.php
2.mysql.php代碼如下
正常的邏輯思維,壓力增大後,導致數據庫num字段成爲負數,將下面代碼粘貼到自己網站下測試即可。
在test數據庫下,新建一個num(庫存)的表,id字段int類型主鍵自增,num字段int類型
新建一個goods_order(訂單)的表,id字段int主鍵自增,goods_id字段int,user_id字段int類型,
如果發現num字段無法成爲負數,打開sleep(2);訪問量堆積起來即可
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<?php
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header("Content-type: text/html; charset=utf-8");
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$dbms='mysql';
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$host='localhost';
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$dbName='test';
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$user='root';
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$pass='root';
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$dsn="$dbms:host=$host;dbname=$dbName";
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try {
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$dbh = new PDO($dsn, $user, $pass, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8';"));
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echo "連接成功<br/>";
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$sq="select num from num where id=1";
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$rs=$dbh->query($sq);
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$rs->setFetchMode(PDO::FETCH_ASSOC);
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$count = $rs->fetch();
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print_r($count);
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if($count['num']>0){
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$sql="update num set num=num-1 where id=1";
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echo $sql;
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$count = $dbh->exec($sql);
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$sql2="insert into goods_order (goods_id,user_id) values(1,123456789)";
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echo $sql2;
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$count2 = $dbh->exec($sql2);
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echo "購買成功<br />";
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}
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$dbh = null;
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} catch (PDOException $e) {
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die ("Error!: " . $e->getMessage() . "<br/>");
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}
3.如果開啓
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$sql="update num set num=num-1 where id=1 and (num -1 ) >= 0";
經過測試num字段最小爲0,在壓力測試下代碼運行正常,
想要增大ab壓力併發量測試,
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./ab.exe -c 500 -n 1000 http://192.168.1.244/mysql.php
會出現如下(看來要去linux下搭建apache來測試了)
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This is ApacheBench, Version 2.3 <$Revision: 1706008 $>
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Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
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Licensed to The Apache Software Foundation, http://www.apache.org/
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Benchmarking 192.168.1.244 (be patient)
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Completed 100 requests
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Total of 125 requests completed
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Test aborted after 10 failures
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apr_socket_connect(): ▒▒▒▒Ŀ▒▒▒▒▒▒▒▒▒▒▒ܾ▒▒▒▒▒▒▒▒ӡ▒ (730061)
4.redis測試,搭建好linux下的apache後,訪問linux下的redis.PHP壓力測試槓槓的,不會報錯了
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./ab.exe -c 1000 -n 1000 http://192.168.1.233/redis.php
此壓力下,redis數據正常,不會出現負數
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<?php
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header("content-type:text/html;charset=utf-8");
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$redis = new redis();
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$result = $redis->connect('192.168.1.233',"6379");
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$num = ($redis->get("num"));
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$count=(int)$num;
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echo "總共有:".$count;
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echo "<br/>";
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if($count>0){
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$redis->set("num",$num-1);
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}else{
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}
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var_dump($num);
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?>
5.以上是ab測試,現在分析代碼
先分析redis.php,上面的這個實現在只有一個客戶端的時候可以執行得很好。 但是, 當多個客戶端同時對同一個鍵進行這樣的操作時, 就會產生競爭條件。舉個例子, 如果客戶端 A 和 B 都讀取了鍵原來的值, 比如 2, 那麼兩個客戶端都會將鍵的值設爲 1 , 但正確的結果應該是 0 纔對。
有了 WATCH , 我們就可以輕鬆地解決這類問題了:
因爲redis的性能很高,當num爲2時,ab模擬兩個併發量後num爲1,模擬兩個併發量和watch如下:
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./ab.exe -c 2 -n 2 http://192.168.1.233/redis.php
修復代碼如下,加入watch監聽,確保數據準確性
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<?php
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header("content-type:text/html;charset=utf-8");
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$redis = new redis();
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$result = $redis->connect('192.168.1.233',"6379");
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$redis->watch("num");
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$num = ($redis->get("num"));
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$redis->multi();
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$count=(int)$num;
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echo "總共有:".$count;
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echo "<br/>";
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if($count>0){
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$redis->set("num",$num-1);
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$redis->incr("order");
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$exec = $redis->exec();
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if($exec[0]==true){
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echo "搶購成功,還剩:".($count-1);
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}else{
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echo "很不幸,沒搶到,可以再搶一把";
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}
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}else{
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echo "活動結束";
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}
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?>
設置1000個庫存,讓1000個人去搶,196個人搶到了,數據很精準
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./ab.exe -c 1000 -n 1000 http://192.168.1.233/redis.php
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192.168.1.233:6379> set num 1000
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OK
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192.168.1.233:6379> get num
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"804"
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192.168.1.233:6379> get order
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"196"
6.分析完redis.php,我們來分析MySQL.php
因爲 秒殺後庫存+訂單=秒殺前庫存,所以採用也要採用事物來處理
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<?php
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header("Content-type: text/html; charset=utf-8");
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$dbms='mysql';
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$host='localhost';
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$dbName='test';
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$user='root';
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$pass='root';
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$dsn="$dbms:host=$host;dbname=$dbName";
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try {
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$dbh = new PDO($dsn, $user, $pass, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8';"));
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echo "連接成功<br/>";
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$sq="select num from num where id=1";
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$rs=$dbh->query($sq);
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$rs->setFetchMode(PDO::FETCH_ASSOC);
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$count = $rs->fetch();
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print_r($count);
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if($count['num']>0){
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try{
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$dbh->beginTransaction();
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$sql="update num set num=num-1 where id=1 and (num -1 ) >= 0";
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$row = $dbh->exec($sql);
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if (!$row)
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throw new PDOException('搶購失敗,再搶');
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$sql2="insert into goods_order (goods_id,user_id) values(1,123456789)";
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$row = $dbh->exec($sql2);
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if (!$row)
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throw new PDOException('搶購失敗,再搶');
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$dbh->commit();
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}catch(PDOException $ex){
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$dbh->rollback();
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exit($ex->getMessage());
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}
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}
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$dbh = null;
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} catch (PDOException $e) {
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die ("Error!: " . $e->getMessage() . "<br/>");
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}
7.總結,以上只是解決了秒殺時候,超賣的問題,但是並未考慮秒殺效率,只是做了簡單測試,後期會加入隊列機制處理秒殺