springboot整合lua脚本在Redis实现商品库存扣减

1、目的

使用lua脚本，可以保证多条命令的操作原子性；同时可以减少操作IO（比如说判断redis对应数据是否小于0，小于0就重置为100，这个场景一般是取出来再判断，再存放进行，就至少存在2次IO,用lua脚本一条命令1次IO就解决了,在批量扣减情况存在多次IO，lua脚本1次也可以解决），提高速度，降低IO.

2、使用案列

根据传入的产品标识及数量扣减该产品数量；此处为单个产品扣减，可优化为批量产品传入，lua内部用table处理。

2.1 初始化redis参数

添加产品及库存（hash结构）。添加两种水果的库存。

java 复制代码

// 向Redis中添加数据
redisTemplate.opsForHash().put("productMap", "pro1", "{\"name\":\"苹果\",\"stock\":100}");
redisTemplate.opsForHash().put("productMap", "pro2", "{\"name\":\"西瓜\",\"stock\":1200}");

查看结果：

2.2 业务代码

传入lua脚本，实现对应产品库存数量扣减。(可优化为多产品批量扣减)

通过setnx加锁，防止死锁设置锁超时时间，同时业务执行完手动释放锁。设置锁等待时间、及锁等待轮询获取锁。(eg：自旋释放cpu资源重新抢占资源)

java 复制代码

@Test
public void tete(){
    // 向Redis中添加数据
    redisTemplate.opsForHash().put("productMap", "pro1", "{\"name\":\"苹果\",\"stock\":100}");
    redisTemplate.opsForHash().put("productMap", "pro2", "{\"name\":\"西瓜\",\"stock\":1200}");

    // Lua 脚本字符串    
   String luaScript = "local productKey = KEYS[1]; " +
       "local pro = KEYS[2]; " +
       "local lockKey = KEYS[3]; " +
       "local lockTimeout = tonumber(ARGV[1]); " +
       "local deductAmount = tonumber(ARGV[2]); " +
       "local spinIntervalMs = tonumber(ARGV[3]); " +
       "local maxSpinCount = tonumber(ARGV[4]); " +
       "local lockAcquired = redis.call('setnx', lockKey, 1); " +
       "if lockAcquired == 1 then " +
       "    redis.call('pexpire', lockKey, lockTimeout); " +
       "    local currentValue = redis.call('hget', productKey, pro); " +
       "    if currentValue then " +
       "        local dbObj = cjson.decode(currentValue);" +
       "        local currentStock = tonumber(dbObj.stock); " +
       "        if currentStock >= deductAmount then " +
       "            dbObj.stock = currentStock - deductAmount; " +
       "            local updatedValue = cjson.encode(dbObj); " +
       "            redis.call('hset', productKey, pro, updatedValue); " +
       "            redis.call('del', lockKey); " +  // 释放锁
       "            return true; " +
       "        else " +
       "            return false; " +
       "        end " +
       "    else " +
       "        return false; " +
       "    end " +
       "else " +
       "    local spinCount = 0; " +
       "    while spinCount < maxSpinCount do " +
       "        local lockValue = redis.call('get', lockKey); " +
       "        if not lockValue then " +
       "            lockAcquired = redis.call('setnx', lockKey, 1); " +
       "            if lockAcquired == 1 then " +
       "                redis.call('pexpire', lockKey, lockTimeout); " +
       "                local currentValue = redis.call('hget', productKey, pro); " +
       "                if currentValue then " +
       "                   local dbObj = cjson.decode(currentValue);" +
       "                   local currentStock = tonumber(dbObj.stock); " +
       "                    if currentStock >= deductAmount then " +
       "                        dbObj.stock = currentStock - deductAmount; " +
       "                        local updatedValue = cjson.encode(dbObj); " +
       "                        redis.call('hset', productKey, pro, updatedValue); " +
       "                        redis.call('del', lockKey); " +  
       "                        return true; " +
       "                    else " +
       "                        return false; " +
       "                    end " +
       "                else " +
       "                    return false; " +
       "                end " +
       "            end " +
       "            break; " +
       "        end " +
       "        spinCount = spinCount + 1; " +
       "    end " +
       "    return false; " +
       "end";
    
    // 创建DefaultRedisScript对象
    DefaultRedisScript<Boolean> script = new DefaultRedisScript<>();
    script.setScriptText(luaScript);
    script.setResultType(Boolean.class); // 设置返回类型为Boolean
    // 执行脚本
    Boolean result = (Boolean) redisTemplate.execute(script,
            Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数
            "50000", // ARGV参数第一个：锁过期时间（毫秒）
            "10", // ARGV参数第二个：扣减数量
            "1000",// ARGV参数第3个：等待时间
            "5");// ARGV参数第4个：轮询次数
    System.out.println("result1:"+result);
    Boolean result2 = (Boolean) redisTemplate.execute(script,
            Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数
            "50000", // ARGV参数第一个：锁过期时间（毫秒）
            "10", // ARGV参数第二个：扣减数量
            "1000",
            "5");
    System.out.println("result2:"+result2);
    Boolean result3 = (Boolean) redisTemplate.execute(script,
            Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数
            "50000", // ARGV参数第一个：锁过期时间（毫秒）
            "10", // ARGV参数第二个：扣减数量
            "1000",
            "5");
    System.out.println("result3:"+result3);
    if (result2) {
        System.out.println("Stock deduction successful.");
    } else {
        System.out.println("Insufficient stock or lock already acquired.");
    }
    // 验证库存是否正确扣减
    Object updatedValue = redisTemplate.opsForHash().get("productMap", "pro1");
    System.out.println(updatedValue);
    Boolean result5 = (Boolean) redisTemplate.execute(script,
            Collections.unmodifiableList(List.of("productMap","pro2","lock:pro2")), // KEYS参数
            "5000", // ARGV参数第一个：锁过期时间（毫秒）
            "500", // ARGV参数第二个：扣减数量
            "1000",
            "5");
}

2.3 正常执行结果

2.4 若获取锁超时，则会出现扣减失败

脚本执行时间过长会导致。（此处可通过删除手动释放锁实现：模拟业务耗时过长没办法手动释放锁需等待锁国企时间）

第二个扣减等待超时。可通过设置调整添加自旋时间重试或业务代码判断重试机制