Redis中的事务和Redis乐观锁详解

127.0.0.1:6379> multi
OK
127.0.0.1:6379> set user:001 zhangsan
QUEUED
127.0.0.1:6379> set user:002 lisi
QUEUED
127.0.0.1:6379> get user:001
QUEUED
127.0.0.1:6379> exec
1) OK
2) OK
3) "zhangsan"


127.0.0.1:6379> multi
OK
127.0.0.1:6379> set user:001 xiaoming
QUEUED
127.0.0.1:6379> set user:002 xiaozhang
QUEUED
127.0.0.1:6379> discard    # 使用discard命令取消队列
OK
127.0.0.1:6379> exec    # 执行exec报错
(error) ERR EXEC without MULTI

# watch 命令演示

# 客户端2，在客户端1执行exec之前，执行 set user:001 xiaoming，客户端1的事务被打断
127.0.0.1:6379> get user:001
"zhangsan"
127.0.0.1:6379> watch user:001
OK
127.0.0.1:6379> multi
OK
127.0.0.1:6379> set user:001 lisi
QUEUED
127.0.0.1:6379> exec   # 客户端1的事务被打断
(nil)
127.0.0.1:6379> get user:001
"xiaoming"

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
        </dependency>

spring:
  redis:
    host: 192.168.235.131
    port: 6379
    database: 0
    connect-timeout: 1800000
    password: 123456
    lettuce:
      pool:
        #连接池最大连接数（使用负值表示没有限制）
        max-active: 20
        #最大阻塞等待时间(负数表示没限制)
        max-wait: -1
        #连接池中的最大空闲连接
        max-idle: 8
        #连接池中的最小空闲连接
        min-idle: 0

@Service
@Slf4j
public class OrderServiceImpl implements OrderService {
    @Autowired
    private StringRedisTemplate redisTemplate;
    //库存
    private final String STOCK_KEY="stock:num";
    //秒杀成功的用户
    private final String USER_KEY="success:user";
    /**
     * Redis乐观锁秒杀案例
     * @param userId  用户ID
     * @return
     */
    @Override
    public boolean secKill(String userId) {
        Object stockObj = redisTemplate.opsForValue().get(STOCK_KEY);
        if (stockObj==null){
            log.info("库存为空，秒杀还未开始！");
            return false;
        }
        int stockNum=Integer.parseInt(stockObj.toString());
        if (stockNum<=0){
            log.info("库存为0，秒杀已经结束！");
            return false;
        }
        //判断当前用户是否已经秒杀成功
        Boolean member = redisTemplate.opsForSet().isMember(USER_KEY, userId);
        if (member){
            log.info("您已经秒杀成功，不能重复参与！");
            return false;
        }
        List txList =redisTemplate.execute(new SessionCallback<List<Object>>() {
           @Override
           public List<Object> execute(RedisOperations operations) throws DataAccessException {
               //监听库存
                operations.watch(STOCK_KEY);
               //开启事务
               operations.multi();
               //扣减库存
               operations.opsForValue().decrement(STOCK_KEY);
               //把秒杀成功的用户加入到set集合
               operations.opsForSet().add(USER_KEY,userId);
               //执行事务
               List<Object> result=operations.exec();
               return result;
           }
       });
        if (txList==null||txList.size()==0){
            log.info("用户:{}，秒杀失败",userId);
            return false;
        }
        log.info("用户:{}，秒杀成功",userId);
        return true;
    }
}

/**
 * 秒杀
 * @return
 */
@RequestMapping("secKill")
public String secKill(){
    String userId= UUID.randomUUID().toString();
    boolean res = orderService.secKill(userId);
    if (res){
        return "秒杀成功";
    }else {
        return "秒杀失败";
    }
}

ab -n 500 -c 100  http://192.168.1.171/order/secKill