Redis——某马点评day03——part2：秒杀业务异步优化

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);
    }
}