springboot+websocket实现并发抢红包功能

概述

抢红包功能作为几大高并发场景中典型，应该如何实现？

源码地址：https://gitee.com/tech-famer/farmer-redpacket

分析

参考微信抢红包功能，将抢红包分成一下几个步骤：

发红包；主要填写红包信息，生成红包记录
红包支付回调；用户发红包支付成功后，收到微信支付付款成功的回调，生成指定数量的红包。
抢红包；用户并发抢红包。
拆红包；记录用户抢红包记录，转账抢到的红包金额。

效果展示

项目使用sessionId模拟用户，示例打开俩个浏览器窗口模拟两个用户。

在这里插入图片描述

设计开发

表结构设计

红包记录在 redpacket 表中，用户领取红包详情记录在 redpacket_detail 表中。

CREATE DATABASE  `redpacket`;

use `redpacket`;

CREATE TABLE `redpacket`.`redpacket` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
  `packet_no` varchar(32) NOT NULL COMMENT '订单号',
  `amount` decimal(5,2) NOT NULL COMMENT '红包金额最高10000.00元',
  `num` int(11) NOT NULL COMMENT '红包数量',
  `order_status` int(4) NOT NULL DEFAULT '0' COMMENT '订单状态：0初始、1待支付、2支付成功、3取消',
  `pay_seq` varchar(32) DEFAULT NULL COMMENT '支付流水号',
  `create_time` datetime NOT NULL COMMENT '创建时间',
  `user_id` varchar(32) NOT NULL COMMENT '用户ID',
  `update_time` datetime NOT NULL COMMENT '更新时间',
  `pay_time` datetime DEFAULT NULL COMMENT '支付时间',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COMMENT='红包订单表';

CREATE TABLE `redpacket`.`redpacket_detail` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
  `packet_id` bigint(20) NOT NULL COMMENT '红包ID',
  `amount` decimal(5,2) NOT NULL COMMENT '红包金额',
  `received` int(1) NOT NULL DEFAULT '0' COMMENT '是否领取0未领取、1已领取',
  `create_time` datetime NOT NULL COMMENT '创建时间',
  `update_time` datetime NOT NULL COMMENT '更新时间',
  `user_id` varchar(32) DEFAULT NULL COMMENT '领取用户',
  `packet_no` varchar(32) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COMMENT='红包详情表';

发红包设计

用户需要填写红包金额、红包数量、备注信息等，生成红包记录，微信收银台下单，返回用户支付。

public RedPacket generateRedPacket(ReqSendRedPacketsVO data,String userId) {
    final BigDecimal amount = data.getAmount();
    //红包数量
    final Integer num = data.getNum();

    //初始化订单
    final RedPacket redPacket = new RedPacket();
    redPacket.setPacketNo(UUID.randomUUID().toString().replace("-", ""));
    redPacket.setAmount(amount);
    redPacket.setNum(num);
    redPacket.setUserId(userId);
    Date now = new Date();
    redPacket.setCreateTime(now);
    redPacket.setUpdateTime(now);
    int i = redPacketMapper.insertSelective(redPacket);
    if (i != 1) {
        throw new ServiceException("生成红包出错", ExceptionType.SYS_ERR);
    }

    //模拟收银台下单
    String paySeq = UUID.randomUUID().toString().replace("-", "");

    //拿到收银台下单结果，更新订单为待支付状态
    redPacket.setOrderStatus(1);//待支付
    redPacket.setPaySeq(paySeq);
    i = redPacketMapper.updateByPrimaryKeySelective(redPacket);
    if (i != 1) {
        throw new ServiceException("生成红包出错", ExceptionType.SYS_ERR);
    }
    return redPacket;
}

在这里插入图片描述

红包支付成功回调设计

用户支付成功后，系统接收到微信回调接口。

更新红包支付状态
二倍均值法生成指定数量红包，并批量入库。红包算法参考：Java实现4种微信抢红包算法
红包总数入redis，设置红包过期时间24小时
websocket通知在线用户收到新的红包

@Transactional(rollbackFor = Exception.class)
public void dealAfterOrderPayCallback(String userId,ReqOrderPayCallbackVO data) {
    RedPacketExample example = new RedPacketExample();
    final String packetNo = data.getPacketNo();
    final String paySeq = data.getPaySeq();
    final Integer payStatus = data.getPayStatus();
    example.createCriteria().andPacketNoEqualTo(packetNo)
            .andPaySeqEqualTo(paySeq)
            .andOrderStatusEqualTo(1);//待支付状态
    //更新订单支付状态
    Date now = new Date();
    RedPacket updateRedPacket = new RedPacket();
    updateRedPacket.setOrderStatus(payStatus);
    updateRedPacket.setUpdateTime(now);
    updateRedPacket.setPayTime(now);
    int i = redPacketMapper.updateByExampleSelective(updateRedPacket, example);
    if (i != 1) {
        throw new ServiceException("订单状态更新失败", ExceptionType.SYS_ERR);
    }

    if (payStatus == 2) {
        RedPacketExample query = new RedPacketExample();
        query.createCriteria().andPacketNoEqualTo(packetNo)
                .andPaySeqEqualTo(paySeq)
                .andOrderStatusEqualTo(2);
        final RedPacket redPacket = redPacketMapper.selectByExample(query).get(0);
        final List<BigDecimal> detailList = getRedPacketDetail(redPacket.getAmount(), redPacket.getNum());
        final int size = detailList.size();
        if (size <= 100) {
            i = detailMapper.batchInsert(detailList, redPacket);
            if (size != i) {
                throw new ServiceException("生成红包失败", ExceptionType.SYS_ERR);
            }
        } else {
            int times = size % 100 == 0 ? size / 100 : (size / 100 + 1);
            for (int j = 0; j < times; j++) {
                int fromIndex = 100 * j;
                int toIndex = 100 * (j + 1) - 1;
                if (toIndex > size - 1) {
                    toIndex = size - 1;
                }
                final List<BigDecimal> subList = detailList.subList(fromIndex, toIndex);
                i = detailMapper.batchInsert(subList, redPacket);
                if (subList.size() != i) {
                    throw new ServiceException("生成红包失败", ExceptionType.SYS_ERR);
                }
            }
        }

        final String redisKey = REDPACKET_NUM_PREFIX + redPacket.getPacketNo();

        String lua = "local i = redis.call('setnx',KEYS[1],ARGV[1])\r\n" +
                "if i == 1 then \r\n" +
                "   local j = redis.call('expire',KEYS[1],ARGV[2])\r\n" +
                "end \r\n" +
                "return i";
        //优化成lua脚本
        final Long execute = redisTemplate.execute(new DefaultRedisScript<>(lua, Long.class), Arrays.asList(redisKey), size, 3600 * 24);
        if (execute != 1L) {
            throw new ServiceException("生成红包失败", ExceptionType.SYS_ERR);
        }
        //websocket通知在线用户收到新的红包
        Websocket.sendMessageToUser(userId, JSONObject.toJSONString(redPacket));
    }
}


/**
 * 红包随机算法
 *
 * @param amount 红包金额
 * @param num    红包数量
 * @return 随机红包集合
 */
private List<BigDecimal> getRedPacketDetail(BigDecimal amount, Integer num) {
    List<BigDecimal> redPacketsList = new ArrayList<>(num);
    //最小红包金额
    final BigDecimal min = new BigDecimal("0.01");
    //最少需要红包金额
    final BigDecimal bigNum = new BigDecimal(num);
    final BigDecimal atLastAmount = min.multiply(bigNum);
    //出去最少红包金额后剩余金额
    BigDecimal remain = amount.subtract(atLastAmount);
    if (remain.compareTo(BigDecimal.ZERO) == 0) {
        for (int i = 0; i < num; i++) {
            redPacketsList.add(min);
        }
        return redPacketsList;
    }

    final Random random = new Random();
    final BigDecimal hundred = new BigDecimal("100");
    final BigDecimal two = new BigDecimal("2");
    BigDecimal redPacket;
    for (int i = 0; i < num; i++) {
        if (i == num - 1) {
            redPacket = remain;
        } else {
            //100内随机获得的整数
            final int rand = random.nextInt(100);
            redPacket = new BigDecimal(rand).multiply(remain.multiply(two).divide(bigNum.subtract(new BigDecimal(i)), 2, RoundingMode.CEILING)).divide(hundred, 2, RoundingMode.FLOOR);
        }
        if (remain.compareTo(redPacket) > 0) {
            remain = remain.subtract(redPacket);
        } else {
            remain = BigDecimal.ZERO;
        }
        redPacketsList.add(min.add(redPacket));
    }

    return redPacketsList;
}

页面加载成功后初始化websocket,监听后端新红包生成成功，动态添加红包到聊天窗口。

$(function (){
    var websocket;
    if('WebSocket' in window) {
        console.log("此浏览器支持websocket");
        websocket = new WebSocket("ws://127.0.0.1:8082/websocket/${session.id}");
    } else if('MozWebSocket' in window) {
        alert("此浏览器只支持MozWebSocket");
    } else {
        alert("此浏览器只支持SockJS");
    }
    websocket.onopen = function(evnt) {
        console.log("链接服务器成功!")
    };
    websocket.onmessage = function(evnt) {
        console.log(evnt.data);
        var json = eval('('+evnt.data+ ')');
        obj.addPacket(json.id,json.packetNo,json.userId)

    };
    websocket.onerror = function(evnt) {};
    websocket.onclose = function(evnt) {
        console.log("与服务器断开了链接!")
    }
});

抢红包设计

抢红包设计高并发，本地单机项目，通过原子Integer控制抢红包接口并发限制为20，

private AtomicInteger receiveCount = new AtomicInteger(0);

@PostMapping("/receive")
public CommonJsonResponse receiveOne(@Validated @RequestBody CommonJsonRequest<ReqReceiveRedPacketVO> vo) {
    Integer num = null;
    try {
        //控制并发不要超过20
        if (receiveCount.get() > 20) {
            return new CommonJsonResponse("9999", "太快了");
        }
        num = receiveCount.incrementAndGet();
        final String s = orderService.receiveOne(vo.getData());
        return StringUtils.isEmpty(s) ? CommonJsonResponse.ok() : new CommonJsonResponse("9999", s);
    } finally {
        if (num != null) {
            receiveCount.decrementAndGet();
        }
    }
}

对于没有领取过该红包的用户，在红包没有过期且红包还有剩余的情况下，抢红包成功，记录成功标识入redis,设置标识过期时间为5秒。

public String receiveOne(ReqReceiveRedPacketVO data) {
    final Long redPacketId = data.getPacketId();
    final String redPacketNo = data.getPacketNo();
    final String redisKey = REDPACKET_NUM_PREFIX + redPacketNo;
    if (!redisTemplate.hasKey(redisKey)) {
        return "红包已经过期";
    }
    final Integer num = (Integer) redisTemplate.opsForValue().get(redisKey);
    if (num <= 0) {
        return "红包已抢完";
    }
    RedPacketDetailExample example = new RedPacketDetailExample();
    example.createCriteria().andPacketIdEqualTo(redPacketId)
            .andReceivedEqualTo(1)
            .andUserIdEqualTo(data.getUserId());
    final List<RedPacketDetail> details = detailMapper.selectByExample(example);
    if (!details.isEmpty()) {
        return "该红包已经领取过了";
    }
    final String receiveKey = REDPACKET_RECEIVE_PREFIX + redPacketNo + ":" + data.getUserId();

    //优化成lua脚本
    String lua = "local i = redis.call('setnx',KEYS[1],ARGV[1])\r\n" +
            "if i == 1 then \r\n" +
            "   local j = redis.call('expire',KEYS[1],ARGV[2])\r\n" +
            "end \r\n" +
            "return i";
    //优化成lua脚本
    final Long execute = redisTemplate.execute(new DefaultRedisScript<>(lua, Long.class), Arrays.asList(receiveKey), 1, 5);
    if (execute != 1L) {
        return "太快了";
    }
    return "";
}

拆红包设计

在用户抢红包成功标识未过期的状态下，且红包未过期红包未领完时，从数据库中领取一个红包，领取成功将领取记录写入redis以供查询过期时间为48小时。

@Transactional(rollbackFor = Exception.class)
public String openRedPacket(ReqReceiveRedPacketVO data) {
    final Long packetId = data.getPacketId();
    final String packetNo = data.getPacketNo();
    final String userId = data.getUserId();
    final String redisKey = REDPACKET_NUM_PREFIX + packetNo;
    Long num = null;
    try {
        final String receiveKey = REDPACKET_RECEIVE_PREFIX + packetNo + ":" + userId;
        if (!redisTemplate.hasKey(receiveKey)) {
            log.info("未获取到红包资格，packet:{},user:{}", packetNo, userId);
            throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
        }
        redisTemplate.delete(receiveKey);
        if (!redisTemplate.hasKey(redisKey)) {
            log.info("红包过期了，packet:{}", packetNo);
            throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
        }
        num = redisTemplate.opsForValue().increment(redisKey, -1);
        if (num < 0L) {
            log.info("红包领完了，packet:{}", packetNo);
            throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
        }
        final int i = detailMapper.receiveOne(packetId, packetNo, userId);
        if (i != 1) {
            log.info("红包真的领完了，packet:{}", packetNo);
            throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
        }
        RedPacketDetailExample example = new RedPacketDetailExample();
        example.createCriteria().andPacketIdEqualTo(packetId)
                .andReceivedEqualTo(1)
                .andUserIdEqualTo(userId);
        final List<RedPacketDetail> details = detailMapper.selectByExample(example);
        if (details.size() != 1) {
            log.info("已经领取过了，packet:{}，user:{}", packetNo, userId);
            throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
        }
        //处理加款
        log.info("抢到红包金额{}，packet:{}，user:{}", details.get(0).getAmount(), packetNo, userId);
        final String listKey = REDPACKET_LIST_PREFIX + packetNo;
        redisTemplate.opsForList().leftPush(listKey,details.get(0));
        redisTemplate.expire(redisKey, 48, TimeUnit.HOURS);
        return "" + details.get(0).getAmount();
    } catch (Exception e) {
        if (num != null) {
            redisTemplate.opsForValue().increment(redisKey, 1L);
        }
        log.warn("打开红包异常", e);
        throw new ServiceException("红包飞走了", ExceptionType.SYS_ERR);
    }
}

其中 detailMapper.receiveOne(packetId, packetNo, userId); sql如下，将指定红包记录下未领取的红包更新一条未当前用户已经领取，若成功更新一条则表示领取成功，否则领取失败。

update redpacket_detail d
set received = 1,update_time = now(),user_id = #{userId,jdbcType=VARCHAR}
where received = 0
and packet_id = #{packetId,jdbcType=BIGINT}
and packet_no = #{packetNo,jdbcType=VARCHAR}
and user_id is null
limit 1

获取红包领取记录设计

直接充redis中获取用户领取记录，没有则直接获取数据库并同步至redis。

public RespReceiveListVO receiveList(ReqReceiveListVO data) {
    //红包记录redisKey
    final String packetNo = data.getPacketNo();
    final String redisKey = REDPACKET_LIST_PREFIX + packetNo;
    if (!redisTemplate.hasKey(redisKey)) {
        RedPacketDetailExample example = new RedPacketDetailExample();
        example.createCriteria().andPacketNoEqualTo(packetNo)
                .andReceivedEqualTo(1);
        final List<RedPacketDetail> list = detailMapper.selectByExample(example);
        redisTemplate.opsForList().leftPushAll(redisKey, list);
        redisTemplate.expire(redisKey, 24, TimeUnit.HOURS);
    }
    List retList = redisTemplate.opsForList().range(redisKey, 0, -1);
    final Object collect = retList.stream().map(item -> {
        final JSONObject packetDetail = (JSONObject) item;
        return ReceiveRecordVO.builder()
                .amount(packetDetail.getBigDecimal("amount"))
                .receiveTime(packetDetail.getDate("updateTime"))
                .userId(packetDetail.getString("userId"))
                .packetId(packetDetail.getLong("redpacketId"))
                .packetNo(packetDetail.getString("redpacketNo"))
                .build();
    }).collect(Collectors.toList());
    return RespReceiveListVO.builder().list((List) collect).build();
}