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。
// 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)
@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
