看下面代碼,一個(gè)簡單的減庫存模擬.
一,并發(fā)扣庫存
1.原始數(shù)據(jù)里面有100個(gè)庫存
image.png
2.下面進(jìn)行減庫存操作,代碼如下所示
$model = new Test();
$data = $model->get(1);
$count = $data['count'];
$model->update(['id' => 1, 'count' => $count - 1]);
3.并發(fā)10,模擬100個(gè)請求
ab.exe -c 10 -n 100 http://www.tp5.net/
哈哈, 理論上count應(yīng)該是0對吧,但是我們看看實(shí)際的結(jié)果
image.png
庫存出錯(cuò)了吧,因?yàn)橥瑫r(shí)讀這個(gè)數(shù)據(jù)的時(shí)候,會出現(xiàn)兩個(gè)請求讀到的都是90,這樣后面就錯(cuò)了
4.我們利用mysql的自減函數(shù),換一個(gè)代碼試試
$model = new Test();
$model->where('id', 1)->setDec('count');
正常了,變成0了
image.png
$model = new Test();
$model->where('id', 1)->setDec('count');
二,并發(fā)新增數(shù)據(jù)
1.100個(gè)并發(fā),這時(shí)候不在同一條數(shù)據(jù),需要插入
$model = new Test();
$data = $model->order('id desc')->find();
$count = $data['count'];
$new_count = $count -1;
$model->insert(['count'=>$new_count]);
ab.exe -c 100 -n 1000 http://www.tp5.net/
image.png
看到?jīng)]有,出現(xiàn)了兩條一模一樣的數(shù)據(jù),出bug了吧.下面用兩種方法來解決
不好意思犯了一個(gè)錯(cuò)誤,不要用mysql保留函數(shù)做字段名,下面改為count改為stock_num
3.文件鎖
$fp = fopen(ROOT_PATH . "./lock.txt", "w+");
if (flock($fp, LOCK_EX)) {
$model = new Test();
$data = $model->order('id desc')->find();
$stock_num = $data['stock_num'];
$new_stock_num = $stock_num - 1;
$model->insert(['stock_num' => $new_stock_num]);
flock($fp, LOCK_UN);
} else {
return data('0', 286, "系統(tǒng)繁忙稍后再試");
}
fclose($fp);
ab.exe -c 100 -n 1000 http://www.tp5.net/
image.png
沒有重復(fù)的,竟然解決了,實(shí)際項(xiàng)目中不推薦這種方法.
4.redis鎖,其實(shí)原理和上面文件鎖的原理類似
5.mysql悲觀鎖+事務(wù)
$model = new Test();
$model->startTrans();
try {
$data = $model->lock(true)->order('id desc')->find();
$stock_num = $data['stock_num'];
$new_stock_num = $stock_num - 1;
$model->insert(['stock_num' => $new_stock_num]);
$model->commit();
} catch (\Exception $exception) {
$model->rollback();
throw $exception;
}
6.mysql樂觀鎖+事務(wù)
$model = new Test();
$TestLogModel = new TestLog();
$model->startTrans();
try {
$data = $model->order('id desc')->find();
$stock_num = $data['stock_num'];
$version = $data['version'];
$new_stock_num =$stock_num-1;
$stock_data = ['stock_num' => $new_stock_num,'version' => $version+1];
$rows = $model->where(['id' => 1,'version' =>$version])->update($stock_data);
if($rows == 1){
$res = $TestLogModel->insert(['number' => $new_stock_num]);
if($res){
$model->commit();
}else{
throw new \Exception('插入失敗');
}
}else{
throw new \Exception('更新失敗');
}
} catch (\Exception $exception) {
$model->rollback();
throw $exception;
}
沒有出現(xiàn)重復(fù)數(shù)據(jù),但是有數(shù)據(jù)丟失了
