看下面代码,一个简单的减库存模拟.
一,并发扣库存
1.原始数据里面有100个库存
image.png
2.下面进行减库存操作,代码如下所示
$model = new Test();
$data = $model->get(1);
$count = $data['count'];
$model->update(['id' => 1, 'count' => $count - 1]);
3.并发10,模拟100个请求
ab.exe -c 10 -n 100 http://www.tp5.net/
哈哈, 理论上count应该是0对吧,但是我们看看实际的结果
image.png
库存出错了吧,因为同时读这个数据的时候,会出现两个请求读到的都是90,这样后面就错了
4.我们利用mysql的自减函数,换一个代码试试
$model = new Test();
$model->where('id', 1)->setDec('count');
正常了,变成0了
image.png
$model = new Test();
$model->where('id', 1)->setDec('count');
二,并发新增数据
1.100个并发,这时候不在同一条数据,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
看到没有,出现了两条一模一样的数据,出bug了吧.下面用两种方法来解决
不好意思犯了一个错误,不要用mysql保留函数做字段名,下面改为count改为stock_num
3.文件锁
$fp = fopen(ROOT_PATH . "./lock.txt", "w+");
if (flock($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, "系统繁忙稍后再试");
}
fclose($fp);
ab.exe -c 100 -n 1000 http://www.tp5.net/
image.png
没有重复的,竟然解决了,实际项目中不推荐这种方法.
4.redis锁,其实原理和上面文件锁的原理类似
5.mysql悲观锁+事务
$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乐观锁+事务
$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('插入失败');
}
}else{
throw new \Exception('更新失败');
}
} catch (\Exception $exception) {
$model->rollback();
throw $exception;
}
没有出现重复数据,但是有数据丢失了
