高并发抢购
1 <?php
2 $conn=mysql_connect("localhost","big","123456");
3 if(!$conn){
4 echo "connect failed";
5 exit;
6 }
7 mysql_select_db("big",$conn);
8 mysql_query("set names utf8");
9
10 $price=10;
11 $user_id=1;
12 $goods_id=1;
13 $sku_id=11;
14 $number=1;
15
16 //生成唯一订单
17 function build_order_no(){
18 return date('ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);
19 }
20 //记录日志
21 function insertLog($event,$type=0){
22 global $conn;
23 $sql="insert into ih_log(event,type)
24 values('$event','$type')";
25 mysql_query($sql,$conn);
26 }
27
28 //模拟下单操作
29 //库存是否大于0
30 $sql="select number from ih_store where goods_id='$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
31 $rs=mysql_query($sql,$conn);
32 $row=mysql_fetch_assoc($rs);
33 if($row['number']>0){//高并发下会导致超卖
34 $order_sn=build_order_no();
35 //生成订单
36 $sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price)
37 values('$order_sn','$user_id','$goods_id','$sku_id','$price')";
38 $order_rs=mysql_query($sql,$conn);
39
40 //库存减少
41 $sql="update ih_store set number=number-{$number} where sku_id='$sku_id'";
42 $store_rs=mysql_query($sql,$conn);
43 if(mysql_affected_rows()){
44 insertLog('库存减少成功');
45 }else{
46 insertLog('库存减少失败');
47 }
48 }else{
49 insertLog('库存不够');
50 }
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
1 //库存减少
2 $sql="update ih_store set number=number-{$number} where sku_id='$sku_id' and number>0";
3 $store_rs=mysql_query($sql,$conn);
4 if(mysql_affected_rows()){
5 insertLog('库存减少成功');
6 }
优化方案2：使用MySQL的事务，锁住操作的行
1 <?php
2 $conn=mysql_connect("localhost","big","123456");
3 if(!$conn){
4 echo "connect failed";
5 exit;
6 }
7 mysql_select_db("big",$conn);
8 mysql_query("set names utf8");
9
10 $price=10;
11 $user_id=1;
12 $goods_id=1;
13 $sku_id=11;
14 $number=1;
15
16 //生成唯一订单号
17 function build_order_no(){
18 return date('ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);
19 }
20 //记录日志
21 function insertLog($event,$type=0){
22 global $conn;
23 $sql="insert into ih_log(event,type)
24 values('$event','$type')";
25 mysql_query($sql,$conn);
26 }
27
28 //模拟下单操作
29 //库存是否大于0
30 mysql_query("BEGIN"); //开始事务
31 $sql="select number from ih_store where goods_id='$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
32 $rs=mysql_query($sql,$conn);
33 $row=mysql_fetch_assoc($rs);
34 if($row['number']>0){
35 //生成订单
36 $order_sn=build_order_no();
37 $sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price)
38 values('$order_sn','$user_id','$goods_id','$sku_id','$price')";
39 $order_rs=mysql_query($sql,$conn);
40
41 //库存减少
42 $sql="update ih_store set number=number-{$number} where sku_id='$sku_id'";
43 $store_rs=mysql_query($sql,$conn);
44 if(mysql_affected_rows()){
45 insertLog('库存减少成功');
46 mysql_query("COMMIT");//事务提交即解锁
47 }else{
48 insertLog('库存减少失败');
49 }
50 }else{
51 insertLog('库存不够');
52 mysql_query("ROLLBACK");
53 }
优化方案3：使用非阻塞的文件排他锁
1 <?php
2 $conn=mysql_connect("localhost","root","123456");
3 if(!$conn){
4 echo "connect failed";
5 exit;
6 }
7 mysql_select_db("big-bak",$conn);
8 mysql_query("set names utf8");
9
10 $price=10;
11 $user_id=1;
12 $goods_id=1;
13 $sku_id=11;
14 $number=1;
15
16 //生成唯一订单号
17 function build_order_no(){
18 return date('ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);
19 }
20 //记录日志
21 function insertLog($event,$type=0){
22 global $conn;
23 $sql="insert into ih_log(event,type)
24 values('$event','$type')";
25 mysql_query($sql,$conn);
26 }
27
28 $fp = fopen("lock.txt", "w+");
29 if(!flock($fp,LOCK_EX | LOCK_NB)){
30 echo "系统繁忙，请稍后再试";
31 return;
32 }
33 //下单
34 $sql="select number from ih_store where goods_id='$goods_id' and sku_id='$sku_id'";
35 $rs=mysql_query($sql,$conn);
36 $row=mysql_fetch_assoc($rs);
37 if($row['number']>0){//库存是否大于0
38 //模拟下单操作
39 $order_sn=build_order_no();
40 $sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price)
41 values('$order_sn','$user_id','$goods_id','$sku_id','$price')";
42 $order_rs=mysql_query($sql,$conn);
43
44 //库存减少
45 $sql="update ih_store set number=number-{$number} where sku_id='$sku_id'";
46 $store_rs=mysql_query($sql,$conn);
47 if(mysql_affected_rows()){
48 insertLog('库存减少成功');
49 flock($fp,LOCK_UN);//释放锁
50 }else{
51 insertLog('库存减少失败');
52 }
53 }else{
54 insertLog('库存不够');
55 }
56 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
1 <?php
2 $store=1000;
3 $redis=new Redis();
4 $result=$redis->connect('127.0.0.1',6379);
5 $res=$redis->llen('goods_store');
6 echo $res;
7 $count=$store-$res;
8 for($i=0;$i<$count;$i++){
9 $redis->lpush('goods_store',1);
10 }
11 echo $redis->llen('goods_store');
抢购、描述逻辑
1 <?php
2 $conn=mysql_connect("localhost","big","123456");
3 if(!$conn){
4 echo "connect failed";
5 exit;
6 }
7 mysql_select_db("big",$conn);
8 mysql_query("set names utf8");
9
10 $price=10;
11 $user_id=1;
12 $goods_id=1;
13 $sku_id=11;
14 $number=1;
15
16 //生成唯一订单号
17 function build_order_no(){
18 return date('ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);
19 }
20 //记录日志
21 function insertLog($event,$type=0){
22 global $conn;
23 $sql="insert into ih_log(event,type)
24 values('$event','$type')";
25 mysql_query($sql,$conn);
26 }
27
28 //模拟下单操作
29 //下单前判断redis队列库存量
30 $redis=new Redis();
31 $result=$redis->connect('127.0.0.1',6379);
32 $count=$redis->lpop('goods_store');
33 if(!$count){
34 insertLog('error:no store redis');
35 return;
36 }
37
38 //生成订单
39 $order_sn=build_order_no();
40 $sql="insert into ih_order(order_sn,user_id,goods_id,sku_id,price)
41 values('$order_sn','$user_id','$goods_id','$sku_id','$price')";
42 $order_rs=mysql_query($sql,$conn);
43
44 //库存减少
45 $sql="update ih_store set number=number-{$number} where sku_id='$sku_id'";
46 $store_rs=mysql_query($sql,$conn);
47 if(mysql_affected_rows()){
48 insertLog('库存减少成功');
49 }else{
50 insertLog('库存减少失败');
51 }
