异步秒杀思路
原本的流程是如下所示，必须从开始到创建订单成功才会返回响应。就像饭店里面从下单到上菜都是一个人在服务，就导致服务员利用率很低，后一个顾客要等到前一个顾客上完菜才可以下单。
最简单的优化就是加员工，一次性就可以服务两个顾客。但是更好的优化是，只让一个服务员去记录下单信息，然后让后厨根据下单依次上菜即可。后面的顾客就可以不用等那么久了。
这个业务场景分为两个部分，对秒杀资格的判断和减库存下单，一个是查数据库，一个是改数据库，速度差异很大，所以这里可以将两个部分分给两个线程去执行。主线程判断购买资格，副线程负责减库存下单。
然后针对要查询数据库的操作也可以优化，将数据存在redis，判断有秒杀资格之后直接返回成功信息给用户，然后后续操作根据消息队列里面的消息进行异步执行。
将优惠券信息先存在redis里面，到时候下单先操作redis，再去操作mysql.然后用一个set去存储所有下过单的用户的id，防止重复下单。
基于Redis完成秒杀资格判断
1.保存优惠券信息到Redis
@Service
public class VoucherServiceImpl extends ServiceImpl<VoucherMapper, Voucher> implements IVoucherService {
@Resource
private ISeckillVoucherService seckillVoucherService;
@Resource
private StringRedisTemplate stringRedisTemplate;
@Override
public Result queryVoucherOfShop(Long shopId) {
// 查询优惠券信息
...
// 返回结果
...
}
@Override
@Transactional
public void addSeckillVoucher(Voucher voucher) {
// 保存优惠券
...
// 保存秒杀信息
...
//保存秒杀库存到Redis
stringRedisTemplate.opsForValue().set(SECKILL_STOCK_KEY+voucher.getId(),voucher.getStock().toString());
}
}2.基于Lua脚本判断是否下单成功
-- 1.参数列表
-- 1.1 优惠券id
local voucherId=ARGV[1]
-- 1.2 用户id
local userId=ARGV[2]
-- 2.数据key
-- 2.1库存key
local stockKey='seckill:stock:'..voucherId
-- 2.2.订单key
local orderKey='seckill:order:'..voucherId
-- 3.脚本业务
-- 3.1.判断库存是否充足 get stockKey
if(tonumber(redis.call('get',stockKey))<= 0) then--获取到字符串转成数值类型
-- 3.2. 库存不足 返回1
return 1
end
-- 3.2 判断用户是否下单 SISMEMBER orderKey userId
if(redis.call('sismember',orderKey,userId)==1) then
--3.3存在，说明是重复下单,返回2
return 2
end
-- 3.4.扣减库存 incrby stockKey -1
redis.call('incrby',stockKey,-1)
-- 3.5.下单(保存用户) sadd orderKey userId
redis.call('add',orderKey,userId)
改造秒杀下单资格判断业务
private static final DefaultRedisScript<Long> SECKILL_SCRIPT;
static{
SECKILL_SCRIPT=new DefaultRedisScript<>();
SECKILL_SCRIPT.setLocation(new ClassPathResource("seckill.lua"));
SECKILL_SCRIPT.setResultType(Long.class);
}
@Override
public Result seckillVoucher(Long voucherId) {
//获取用户
Long userId = UserHolder.getUser().getId();
//1.执行Lua脚本
Long result = stringRedisTemplate.execute(
SECKILL_SCRIPT,
Collections.emptyList(),
voucherId.toString(), userId.toString()
);
int r = result.intValue();
//2.判断结果是否为0
if(r!=0){
//2.1.不为0，代表没有购买资格
return Result.fail(r==1?"库存不足":"不能重复下单");
}
//2.2为0，有购买资格，把下单信息保存到阻塞队列
long orderId = redisIdWorker.nextId("order");
//TODO 保存阻塞队列
//3.返回订单id
return Result.ok(orderId);
}基于阻塞队列实现秒杀异步下单
3. 封装优惠券id和用户id进阻塞队列4.获取阻塞队列消息，实现异步下单
public interface IVoucherOrderService extends IService<VoucherOrder> {
Result seckillVoucher(Long voucherId);
void createVoucherOrder(VoucherOrder voucherOrder);
}@Service
@Slf4j
public class VoucherOrderServiceImpl extends ServiceImpl<VoucherOrderMapper, VoucherOrder> implements IVoucherOrderService {
@Resource
private RedisIdWorker redisIdWorker;
@Resource
private ISeckillVoucherService seckillVoucherService;
@Resource
private StringRedisTemplate stringRedisTemplate;
@Resource
private RedissonClient redissonClient;
private static final DefaultRedisScript<Long> SECKILL_SCRIPT;
static{
SECKILL_SCRIPT=new DefaultRedisScript<>();
SECKILL_SCRIPT.setLocation(new ClassPathResource("seckill.lua"));
SECKILL_SCRIPT.setResultType(Long.class);
}
private BlockingQueue<VoucherOrder>orderTasks=new ArrayBlockingQueue<>(1024*1024);
private static final ExecutorService SECKILL_ORDER_EXECUTOR= Executors.newSingleThreadExecutor();
@PostConstruct //当前类初始化完毕时就执行
private void init(){
SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
}
private class VoucherOrderHandler implements Runnable{
@Override
public void run() {
while(true){
try {
//1.获取队列中的订单信息
VoucherOrder voucherOrder = orderTasks.take();
//2.创建订单
handleVoucherOrder(voucherOrder);
} catch (InterruptedException e) {
log.error("处理订单异常",e);
}
}
}
}
//处理订单
private void handleVoucherOrder(VoucherOrder voucherOrder) {
//1. 获取用户id
Long userId = voucherOrder.getUserId();
//2.创建锁对象
RLock lock = redissonClient.getLock("lock:order:" + userId);
//3.获取锁
// boolean isLock = lock.trylock(1200);
boolean isLock = lock.tryLock();
//4.判断是否获取锁成功
if(!isLock){
//获取锁失败,返回报错
log.error("不允许重复下单"); //理论上不会有问题，redis已经判断过了
}
try {
//取到代理对象
proxy.createVoucherOrder(voucherOrder);
}finally {
//释放锁
lock.unlock();
}
}
private IVoucherOrderService proxy;
@Override
public Result seckillVoucher(Long voucherId) {
//获取用户
Long userId = UserHolder.getUser().getId();
//1.执行Lua脚本
Long result = stringRedisTemplate.execute(
SECKILL_SCRIPT,
Collections.emptyList(),
voucherId.toString(), userId.toString()
);
int r = result.intValue();
//2.判断结果是否为0
if(r!=0){
//2.1.不为0，代表没有购买资格
return Result.fail(r==1?"库存不足":"不能重复下单");
}
//2.2为0，有购买资格，把下单信息保存到阻塞队列
//TODO 保存阻塞队列
VoucherOrder voucherOrder = new VoucherOrder();
//2.3订单Id
long orderId = redisIdWorker.nextId("order");
voucherOrder.setId(orderId);
//2.4用户Id
voucherOrder.setUserId(userId);
//2.5代金券Id
voucherOrder.setVoucherId(voucherId);
//2.6放入阻塞队列
orderTasks.add(voucherOrder);
//3.获取代理对象 为了让后序线程可以拿到代理对象，可以放在成员变量或者是voucherOrder里面
proxy =(IVoucherOrderService) AopContext.currentProxy();
//4.返回订单id
return Result.ok(orderId);
}
@Override
@Transactional
public void createVoucherOrder(VoucherOrder voucherOrder) {
//5.一人一单
Long userId = voucherOrder.getUserId();
//5.1查询订单
int count = query().eq("user_id", userId).eq("voucher_id", voucherOrder.getVoucherId()).count();
//5.2判断是否存在
if (count > 0) {
//用户已经购买过了
log.error("用户已经购买过一次"); //redis已经判断过了，这里几乎不会出错
return ;
}
//6.扣减库存
boolean success = seckillVoucherService.update()
.setSql("stock = stock - 1") //set stock =stock - 1
.eq("voucher_id", voucherOrder.getVoucherId())
.gt("stock", 0)//where id=? and stock > 0
.update();
if (!success) {
log.error("库存不足"); //这里也几乎不会出错
return ;
}
//7.创建订单
//此处传了voucherOrder进来，就不用重新创建订单了
save(voucherOrder);
}
}
太强了，这个代码.
Redis消息队列
基于List实现消息队列
基于PubSub实现消息队列
Stream消息队列
单消费模式
消费者组模式
使用XACK命令移除已经确认的消息
基于Stream消息队列实现异步秒杀
创建消息队列
XGROUP CREATE stream.orders g1 0 MKSTREAM修改Lua脚本
新增了一个订单id和3.6的操作，使用id作为orderId的key可以直接对应实体类中的属性。
-- 1.参数列表
-- 1.1 优惠券id
local voucherId=ARGV[1]
-- 1.2 用户id
local userId=ARGV[2]
-- 1.3 订单id
local OrderId=ARGV[3]
-- 2.数据key
-- 2.1库存key
local stockKey='seckill:stock:'..voucherId
-- 2.2.订单key
local orderKey='seckill:order:'..voucherId
-- 3.脚本业务
-- 3.1.判断库存是否充足 get stockKey
if(tonumber(redis.call('get',stockKey))<= 0) then--获取到字符串转成数值类型
-- 3.2. 库存不足 返回1
return 1
end
-- 3.2 判断用户是否下单 SISMEMBER orderKey userId
if(redis.call('sismember',orderKey,userId)==1) then
--3.3存在，说明是重复下单,返回2
return 2
end
-- 3.4.扣减库存 incrby stockKey -1
redis.call('incrby',stockKey,-1)
-- 3.5.下单(保存用户) sadd orderKey userId
redis.call('sadd',orderKey,userId)
-- 3.6 发送消息到队列中，XADD stream.orders * k1 v1 k2 v2
redis.call('xadd','stream.orders','*','userId',userId,'voucherId',voucherId,'id',OrderId)
return 0
改造秒杀业务逻辑
private IVoucherOrderService proxy;
@Override
public Result seckillVoucher(Long voucherId) {
//获取用户
Long userId = UserHolder.getUser().getId();
//获取订单ID
long orderId = redisIdWorker.nextId("order");
//1.执行Lua脚本
Long result = stringRedisTemplate.execute(
SECKILL_SCRIPT,
Collections.emptyList(),
voucherId.toString(), userId.toString(),String.valueOf(orderId)
);
int r = result.intValue();
//2.判断结果是否为0
if(r!=0){
//2.1.不为0，代表没有购买资格
return Result.fail(r==1?"库存不足":"不能重复下单");
}
//3.获取代理对象 为了让后序线程可以拿到代理对象，可以放在成员变量或者是voucherOrder里面
proxy =(IVoucherOrderService) AopContext.currentProxy();
//4.返回订单id
return Result.ok(orderId);
}开启线程任务获取消息队列的消息
@PostConstruct //当前类初始化完毕时就执行
private void init(){
SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
}
private class VoucherOrderHandler implements Runnable{
String queueName="stream.orders";
@Override
public void run() {
while(true){
try {
//1.获取消息队列中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 BLOCK 2000 STREAMS stream.order >
List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
Consumer.from("g1", "c1"),
StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
StreamOffset.create(queueName, ReadOffset.lastConsumed())
);
//2.判断消息获取是否成功
if(list==null|| list.isEmpty()) {
//2.1如果获取失败，说明没有消息，继续下一次循环
continue;
}
//3.解析消息中的订单信息
MapRecord<String, Object, Object> record = list.get(0);
Map<Object, Object> values = record.getValue();
VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
//4.如果获取成功，可以下单
handleVoucherOrder(voucherOrder);
//5.ACK确认 SACK stream.orders g1 id
stringRedisTemplate.opsForStream().acknowledge(queueName,"g1",record.getId());
} catch (Exception e) {
log.error("处理订单异常",e);
handlePendingList();
}
}
}
private void handlePendingList() {
while(true){
try {
//1.获取pending-list中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 STREAMS stream.order 0
List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
Consumer.from("g1", "c1"),
StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
StreamOffset.create(queueName, ReadOffset.from("0"))
);
//2.判断消息获取是否成功
if(list==null|| list.isEmpty()) {
//如果获取失败，说明pending-list没有异常消息，结束循环
break;
}
//3.解析消息中的订单信息
MapRecord<String, Object, Object> record = list.get(0);
Map<Object, Object> values = record.getValue();
VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
//4.如果获取成功，可以下单
handleVoucherOrder(voucherOrder);
//5.ACK确认 SACK stream.orders g1 id
stringRedisTemplate.opsForStream().acknowledge(queueName,"g1",record.getId());
} catch (Exception e) {
log.error("处理订单异常",e);
try {
Thread.sleep(50);
} catch (InterruptedException ex) {
throw new RuntimeException(ex);
}
//休眠一会儿后进入下一次循环
}
}
}
}
秒杀业务最终代码
@Service
@Slf4j
public class VoucherOrderServiceImpl extends ServiceImpl<VoucherOrderMapper, VoucherOrder> implements IVoucherOrderService {
@Resource
private RedisIdWorker redisIdWorker;
@Resource
private ISeckillVoucherService seckillVoucherService;
@Resource
private StringRedisTemplate stringRedisTemplate;
@Resource
private RedissonClient redissonClient;
private static final DefaultRedisScript<Long> SECKILL_SCRIPT;
static{
SECKILL_SCRIPT=new DefaultRedisScript<>();
SECKILL_SCRIPT.setLocation(new ClassPathResource("seckill.lua"));
SECKILL_SCRIPT.setResultType(Long.class);
}
private BlockingQueue<VoucherOrder>orderTasks=new ArrayBlockingQueue<>(1024*1024);
private static final ExecutorService SECKILL_ORDER_EXECUTOR= Executors.newSingleThreadExecutor();
@PostConstruct //当前类初始化完毕时就执行
private void init(){
SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
}
private class VoucherOrderHandler implements Runnable{
String queueName="stream.orders";
@Override
public void run() {
while(true){
try {
//1.获取消息队列中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 BLOCK 2000 STREAMS stream.order >
List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
Consumer.from("g1", "c1"),
StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
StreamOffset.create(queueName, ReadOffset.lastConsumed())
);
//2.判断消息获取是否成功
if(list==null|| list.isEmpty()) {
//2.1如果获取失败，说明没有消息，继续下一次循环
continue;
}
//3.解析消息中的订单信息
MapRecord<String, Object, Object> record = list.get(0);
Map<Object, Object> values = record.getValue();
VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
//4.如果获取成功，可以下单
handleVoucherOrder(voucherOrder);
//5.ACK确认 SACK stream.orders g1 id
stringRedisTemplate.opsForStream().acknowledge(queueName,"g1",record.getId());
} catch (Exception e) {
log.error("处理订单异常",e);
handlePendingList();
}
}
}
private void handlePendingList() {
while(true){
try {
//1.获取pending-list中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 STREAMS stream.order 0
List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
Consumer.from("g1", "c1"),
StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
StreamOffset.create(queueName, ReadOffset.from("0"))
);
//2.判断消息获取是否成功
if(list==null|| list.isEmpty()) {
//如果获取失败，说明pending-list没有异常消息，结束循环
break;
}
//3.解析消息中的订单信息
MapRecord<String, Object, Object> record = list.get(0);
Map<Object, Object> values = record.getValue();
VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
//4.如果获取成功，可以下单
handleVoucherOrder(voucherOrder);
//5.ACK确认 SACK stream.orders g1 id
stringRedisTemplate.opsForStream().acknowledge(queueName,"g1",record.getId());
} catch (Exception e) {
log.error("处理订单异常",e);
try {
Thread.sleep(50);
} catch (InterruptedException ex) {
throw new RuntimeException(ex);
}
//休眠一会儿后进入下一次循环
}
}
}
}
//阻塞队列的写法
/*private static final ExecutorService SECKILL_ORDER_EXECUTOR= Executors.newSingleThreadExecutor();
@PostConstruct //当前类初始化完毕时就执行
private void init(){
SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
}
private class VoucherOrderHandler implements Runnable{
@Override
public void run() {
while(true){
try {
//1.获取队列中的订单信息
VoucherOrder voucherOrder = orderTasks.take();
//2.创建订单
handleVoucherOrder(voucherOrder);
} catch (InterruptedException e) {
log.error("处理订单异常",e);
}
}
}
}*/
//处理订单
private void handleVoucherOrder(VoucherOrder voucherOrder) {
//1. 获取用户id
Long userId = voucherOrder.getUserId();
//2.创建锁对象
RLock lock = redissonClient.getLock("lock:order:" + userId);
//3.获取锁
// boolean isLock = lock.trylock(1200);
boolean isLock = lock.tryLock();
//4.判断是否获取锁成功
if(!isLock){
//获取锁失败,返回报错
log.error("不允许重复下单"); //理论上不会有问题，redis已经判断过了
}
try {
//取到代理对象
proxy.createVoucherOrder(voucherOrder);
}finally {
//释放锁
lock.unlock();
}
}
private IVoucherOrderService proxy;
@Override
public Result seckillVoucher(Long voucherId) {
//获取用户
Long userId = UserHolder.getUser().getId();
//获取订单ID
long orderId = redisIdWorker.nextId("order");
//1.执行Lua脚本
Long result = stringRedisTemplate.execute(
SECKILL_SCRIPT,
Collections.emptyList(),
voucherId.toString(), userId.toString(),String.valueOf(orderId)
);
int r = result.intValue();
//2.判断结果是否为0
if(r!=0){
//2.1.不为0，代表没有购买资格
return Result.fail(r==1?"库存不足":"不能重复下单");
}
//3.获取代理对象 为了让后序线程可以拿到代理对象，可以放在成员变量或者是voucherOrder里面
proxy =(IVoucherOrderService) AopContext.currentProxy();
//4.返回订单id
return Result.ok(orderId);
}
//阻塞队列的写法
/*@Override
public Result seckillVoucher(Long voucherId) {
//获取用户
Long userId = UserHolder.getUser().getId();
//1.执行Lua脚本
Long result = stringRedisTemplate.execute(
SECKILL_SCRIPT,
Collections.emptyList(),
voucherId.toString(), userId.toString()
);
int r = result.intValue();
//2.判断结果是否为0
if(r!=0){
//2.1.不为0，代表没有购买资格
return Result.fail(r==1?"库存不足":"不能重复下单");
}
//2.2为0，有购买资格，把下单信息保存到阻塞队列
// 保存阻塞队列
VoucherOrder voucherOrder = new VoucherOrder();
//2.3订单Id
long orderId = redisIdWorker.nextId("order");
voucherOrder.setId(orderId);
//2.4用户Id
voucherOrder.setUserId(userId);
//2.5代金券Id
voucherOrder.setVoucherId(voucherId);
//2.6放入阻塞队列
orderTasks.add(voucherOrder);
//3.获取代理对象 为了让后序线程可以拿到代理对象，可以放在成员变量或者是voucherOrder里面
proxy =(IVoucherOrderService) AopContext.currentProxy();
//4.返回订单id
return Result.ok(orderId);
}*/
//不使用异步的写法？？
/*@Override
public Result seckillVoucher(Long voucherId) {
//1.查询优惠券
SeckillVoucher voucher = seckillVoucherService.getById(voucherId);
//2.判断秒杀是否开始
if (voucher.getBeginTime().isAfter(LocalDateTime.now())) {
//尚未开始
return Result.fail("秒杀尚未开始");
}
//3.判断秒杀是否已经结束
if (voucher.getEndTime().isBefore(LocalDateTime.now())) {
//尚未开始
return Result.fail("秒杀已经结束");
}
//4.判断库存是否充足
if (voucher.getStock()<1) {
//库存不足
return Result.fail("库存不足");
}
//5.一人一单
Long userId = UserHolder.getUser().getId();
//创建锁对象
// SimpleRedisLock lock = new SimpleRedisLock("order:" + userId, stringRedisTemplate);
RLock lock = redissonClient.getLock("lock:order:" + userId);
//获取锁
// boolean isLock = lock.trylock(1200);
boolean isLock = lock.tryLock();
//判断是否获取锁成功
if(!isLock){
//获取锁失败,返回报错
return Result.fail("不允许重复下单");
}
try {
//取到了当前代理对象
IVoucherOrderService proxy =(IVoucherOrderService) AopContext.currentProxy();
return proxy.createVoucherOrder(voucherId);
}finally {
//释放锁
lock.unlock();
}
}*/
@Override
@Transactional
public void createVoucherOrder(VoucherOrder voucherOrder) {
//5.一人一单
Long userId = voucherOrder.getUserId();
//5.1查询订单
int count = query().eq("user_id", userId).eq("voucher_id", voucherOrder.getVoucherId()).count();
//5.2判断是否存在
if (count > 0) {
//用户已经购买过了
log.error("用户已经购买过一次"); //redis已经判断过了，这里几乎不会出错
return ;
}
//6.扣减库存
boolean success = seckillVoucherService.update()
.setSql("stock = stock - 1") //set stock =stock - 1
.eq("voucher_id", voucherOrder.getVoucherId())
.gt("stock", 0)//where id=? and stock > 0
.update();
if (!success) {
log.error("库存不足"); //这里也几乎不会出错
return ;
}
//7.创建订单
//此处传了voucherOrder进来，就不用重新创建订单了
save(voucherOrder);
}
}
