标签:否则 query date 不同 and tor soc emc 调用
抢购、秒杀是平常很常见的场景,面试的时候面试官也经常会问到,比如问你淘宝中的抢购秒杀是怎么实现的等等。
抢购、秒杀实现很简单,但是有些问题需要解决,主要针对两个问题:
一、高并发对数据库产生的压力
二、竞争状态下如何解决库存的正确减少("超卖"问题)
第一个问题,对于PHP来说很简单,用缓存技术就可以缓解数据库压力,比如memcache,redis等缓存技术。
第二个问题就比较复杂点:
常规写法:
查询出对应商品的库存,看是否大于0,然后执行生成订单等操作,但是在判断库存是否大于0处,如果在高并发下就会有问题,导致库存量出现负数。
<?php $conn =mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql="insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //库存是否大于0 $sq l= "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘"; //解锁 此时ih_store数据中goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘ 的数据被锁住(注3),其它事务必须等待此次事务 提交后才能执行 $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){//高并发下会导致超卖 $order_sn = build_order_no(); //生成订单 $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); }else{ insertLog(‘库存减少失败‘); } }else{ insertLog(‘库存不够‘); }
出现这种情况怎么办呢?来看几种优化方法:
优化方案1:将库存字段number字段设为unsigned,当库存为0时,因为字段不能为负数,将会返回false
//库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘ and number>0"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); }
优化方案2:使用MySQL的事务,锁住操作的行
<?php $conn = mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //库存是否大于0 mysql_query("BEGIN"); //开始事务 $sql = "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘ FOR UPDATE";//此时这条记录被锁住,其它事务必须等待此次事务提交后才能执行 $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){ //生成订单 $order_sn = build_order_no(); $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs =mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); mysql_query("COMMIT");//事务提交即解锁 }else{ insertLog(‘库存减少失败‘); } }else{ insertLog(‘库存不够‘); mysql_query("ROLLBACK"); }
优化方案3:使用非阻塞的文件排他锁
<?php $conn = mysql_connect("localhost","root","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big-bak",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } $fp = fopen("lock.txt", "w+"); if(!flock($fp,LOCK_EX | LOCK_NB)){ echo "系统繁忙,请稍后再试"; return; } //下单 $sql = "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘"; $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){//库存是否大于0 //模拟下单操作 $order_sn = build_order_no(); $sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); flock($fp,LOCK_UN);//释放锁 } else { insertLog(‘库存减少失败‘); } } else { insertLog(‘库存不够‘); } fclose($fp);
优化方案4:使用redis队列,因为pop操作是原子的,即使有很多用户同时到达,也是依次执行,推荐使用(mysql事务在高并发下性能下降很厉害,文件锁的方式也是)
先将商品库存如队列
<?php $store = 1000; $redis = new Redis(); $result = $redis->connect(‘127.0.0.1‘,6379); $res = $redis->llen(‘goods_store‘); echo $res; $count = $store-$res; for($i=0;$i<$count;$i++){ $redis->lpush(‘goods_store‘,1); } echo $redis->llen(‘goods_store‘);
抢购、描述逻辑
<?php $conn = mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //下单前判断redis队列库存量 $redis = new Redis(); $result = $redis->connect(‘127.0.0.1‘,6379); $count = $redis->lpop(‘goods_store‘); if(!$count){ insertLog(‘error:no store redis‘); return; } //生成订单 $order_sn = build_order_no(); $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); }else{ insertLog(‘库存减少失败‘); }
上述只是简单模拟高并发下的抢购,真实场景要比这复杂很多,很多注意的地方,如抢购页面做成静态的,通过ajax调用接口。
再如上面的会导致一个用户抢多个,思路:
需要一个排队队列和抢购结果队列及库存队列。高并发情况,先将用户进入排队队列,用一个线程循环处理从排队队列取出一个用户,判断用户是否已在抢购结果队列,如果在,则已抢购,否则未抢购,库存减1,写数据库,将用户入结果队列。
我之间做商城项目的时候,在秒杀这一块我直接用的redis,这段时间看了看上面的几种方法,虽然各有不同,但是实现目的都一样的,各位自己选择,开心就好。
抢购、秒杀是平常很常见的场景,面试的时候面试官也经常会问到,比如问你淘宝中的抢购秒杀是怎么实现的等等。
抢购、秒杀实现很简单,但是有些问题需要解决,主要针对两个问题:
一、高并发对数据库产生的压力
二、竞争状态下如何解决库存的正确减少("超卖"问题)
第一个问题,对于PHP来说很简单,用缓存技术就可以缓解数据库压力,比如memcache,redis等缓存技术。
第二个问题就比较复杂点:
常规写法:
查询出对应商品的库存,看是否大于0,然后执行生成订单等操作,但是在判断库存是否大于0处,如果在高并发下就会有问题,导致库存量出现负数。
<?php $conn = mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //库存是否大于0 $sql = "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘"; //解锁 此时ih_store数据中goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘ 的数据被锁住(注3),其它事务必须等待此次事务 提交后才能执行 $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){//高并发下会导致超卖 $order_sn = build_order_no(); //生成订单 $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); }else{ insertLog(‘库存减少失败‘); } }else{ insertLog(‘库存不够‘); }
出现这种情况怎么办呢?来看几种优化方法:
优化方案1:将库存字段number字段设为unsigned,当库存为0时,因为字段不能为负数,将会返回false
//库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘ and number>0"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘);
}
优化方案2:使用MySQL的事务,锁住操作的行
<?php $conn = mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //库存是否大于0 mysql_query("BEGIN"); //开始事务 $sql = "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘ FOR UPDATE";//此时这条记录被锁住,其它事务必须等待此次事务提交后才能执行 $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){ //生成订单 $order_sn = build_order_no(); $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); mysql_query("COMMIT");//事务提交即解锁 }else{ insertLog(‘库存减少失败‘); } }else{ insertLog(‘库存不够‘); mysql_query("ROLLBACK"); }
优化方案3:使用非阻塞的文件排他锁
<?php $conn = mysql_connect("localhost","root","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big-bak",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } $fp = fopen("lock.txt", "w+"); if(!flock($fp,LOCK_EX | LOCK_NB)){ echo "系统繁忙,请稍后再试"; return; } //下单 $sql = "select number from ih_store where goods_id=‘$goods_id‘ and sku_id=‘$sku_id‘"; $rs = mysql_query($sql,$conn); $row = mysql_fetch_assoc($rs); if($row[‘number‘]>0){//库存是否大于0 //模拟下单操作 $order_sn = build_order_no(); $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); flock($fp,LOCK_UN);//释放锁 }else{ insertLog(‘库存减少失败‘); } }else{ insertLog(‘库存不够‘); } fclose($fp);
优化方案4:使用redis队列,因为pop操作是原子的,即使有很多用户同时到达,也是依次执行,推荐使用(mysql事务在高并发下性能下降很厉害,文件锁的方式也是)
先将商品库存如队列
?php $store = 1000; $redis = new Redis(); $result = $redis->connect(‘127.0.0.1‘,6379); $res = $redis->llen(‘goods_store‘); echo $res; $count = $store-$res; for($i=0;$i<$count;$i++){ $redis->lpush(‘goods_store‘,1); } echo $redis->llen(‘goods_store‘);
抢购、描述逻辑
<?php $conn = mysql_connect("localhost","big","123456"); if(!$conn){ echo "connect failed"; exit; } mysql_select_db("big",$conn); mysql_query("set names utf8"); $price = 10; $user_id = 1; $goods_id = 1; $sku_id = 11; $number = 1; //生成唯一订单号 function build_order_no(){ return date(‘ymd‘).substr(implode(NULL, array_map(‘ord‘, str_split(substr(uniqid(), 7, 13), 1))), 0, 8); } //记录日志 function insertLog($event,$type=0){ global $conn; $sql = "insert into ih_log(event,type) values(‘$event‘,‘$type‘)"; mysql_query($sql,$conn); } //模拟下单操作 //下单前判断redis队列库存量 $redis = new Redis(); $result = $redis->connect(‘127.0.0.1‘,6379); $count = $redis->lpop(‘goods_store‘); if(!$count){ insertLog(‘error:no store redis‘); return; } //生成订单 $order_sn = build_order_no(); $sql = "insert into ih_order(order_sn,user_id,goods_id,sku_id,price) values(‘$order_sn‘,‘$user_id‘,‘$goods_id‘,‘$sku_id‘,‘$price‘)"; $order_rs = mysql_query($sql,$conn); //库存减少 $sql = "update ih_store set number=number-{$number} where sku_id=‘$sku_id‘"; $store_rs = mysql_query($sql,$conn); if(mysql_affected_rows()){ insertLog(‘库存减少成功‘); }else{ insertLog(‘库存减少失败‘); }
上述只是简单模拟高并发下的抢购,真实场景要比这复杂很多,很多注意的地方,如抢购页面做成静态的,通过ajax调用接口。
再如上面的会导致一个用户抢多个,思路:
需要一个排队队列和抢购结果队列及库存队列。高并发情况,先将用户进入排队队列,用一个线程循环处理从排队队列取出一个用户,判断用户是否已在抢购结果队列,如果在,则已抢购,否则未抢购,库存减1,写数据库,将用户入结果队列。
我之间做商城项目的时候,在秒杀这一块我直接用的redis,这段时间看了看上面的几种方法,虽然各有不同,但是实现目的都一样的,各位自己选择,开心就好。
标签:否则 query date 不同 and tor soc emc 调用
原文地址:https://www.cnblogs.com/dawuge/p/10480807.html