使用lua实现redis分布式锁

逃离我推掉我的手 2022-10-20 13:45 177阅读 0赞

Lua官网

[http://doc.redisfans.com/script/eval.html][http_doc.redisfans.com_script_eval.html]

问题重现：预约功能，用jemter测试，30个不同用户同时预约，2个用户重复发送请求，即重复发送消息场景，结果导致重复消费

避免重复消费方式

1.如第6行，重复原因：第10行，业务逻辑耗时比较长，还没执行第11行，导致6行，执行通过，重复的数据都进来了

2.如第5行+12行，高并发下，加分布式锁，重复请求（具体场景是什么），只有一个能执行业务逻辑。这样不够，6行还是要保留，保证幂等。

分析：分布式锁只能保证高并发下幂等行，无法保证持久幂等。这里注意：分布式锁与existKey，都不是一个固定值，保证10业务逻辑可以并发执行。

高并发与幂等行没有关系。

1 String key = RedisEnum.APPOINT_RECORD_KEY.toKey(reqVO.getLiveId(), reqVO.getUid());
    2 String uniqueVal = UUID.randomUUID().toString();
    3 String lockKey = RedisEnum.APPOINT_RECORD_LOCK_KEY.toKey(reqVO.getLiveId(), reqVO.getUid());
    4 try {
    5    if (redisManager.tryLock(lockKey, uniqueVal, APPOINT_RECORD_LOCK_KEY.expired)) {
     6      Boolean exist = redisManager.existsKey(key);
     7      if (Boolean.TRUE.equals(exist)) {
      8         log.error("saveAppoint exception already appointed reqParam:{}", JSON.toJSONString(reqVO));
       9        throw ExceptionUtils.throwException(LIVE_APPOINTED);
           }
    10 todo 处理业务逻辑
    11 redisManager.put(key, RedisEnum.APPOINT_RECORD_KEY.expired, JSON.toJSONString(reqVO));
        }
    } catch (Exception e) {
        log.error("Saving appoint exception", e);
        throw ExceptionUtils.throwException(LIVE_APPOINTED);
    } finally {
      12  redisManager.releaseLock(lockKey, uniqueVal);
    }
    return false;

参考：

[https://blog.csdn.net/qq\_39736103/article/details/116452752?utm\_medium=distribute.pc\_relevant.none-task-blog-baidujs\_title-0&spm=1001.2101.3001.4242][https_blog.csdn.net_qq_39736103_article_details_116452752_utm_medium_distribute.pc_relevant.none-task-blog-baidujs_title-0_spm_1001.2101.3001.4242]

lua实现

加锁：

public boolean tryLock(String lockKey, String randomUnValue, int expireTime) {
            Jedis jedis = null;
    
            boolean var6;
            try {
                jedis = this.jedisPool.getResource();
                Long result = (Long)jedis.eval(LuaSecript.SETNX_AND_EXPIRE.getScript(), 1, new String[]{lockKey, randomUnValue, String.valueOf(expireTime)});
                if (result != 1L) {
                    return false;
                }
    
                var6 = true;
            } catch (Exception var10) {
                this.logger.error("Try lock failed", var10);
                return false;
            } finally {
                if (jedis != null) {
                    jedis.close();
                }
    
            }
    
            return var6;
        }

public enum LuaSecript {
        SETNX_AND_EXPIRE("local is_existed = redis.call('setnx', KEYS[1], ARGV[1]);if (is_existed == 1) then redis.call('expire', KEYS[1], ARGV[2]);return 1; end; return 0;"),
        DEL_KEY_AND_EQUAL_VAL("if (redis.call('get', KEYS[1]) == ARGV[1]) then return redis.call('del', KEYS[1]);else return 0;end; "),
        ZRANGEBYSCORE_ZREM("local data = redis.call('ZRANGEBYSCORE', KEYS[1], ARGV[1], ARGV[2], 'WITHSCORES', 'LIMIT', ARGV[3], ARGV[4]);if table.getn(data) > 0 then for k,v in pairs(data) do if (k % 2) ~=0 then redis.call('ZREM', KEYS[1], v);end;end;return data;end;");
    
        private String script;
    
        private LuaSecript(String script) {
            this.script = script;
        }
    
        public String getScript() {
            return this.script;
        }
    }

解锁：

public boolean releaseLock(String lockKey, String randomUnValue) {
            Jedis jedis = null;
    
            boolean var5;
            try {
                jedis = this.jedisPool.getResource();
                jedis.eval(LuaSecript.DEL_KEY_AND_EQUAL_VAL.getScript(), 1, new String[]{lockKey, randomUnValue});
                return true;
            } catch (Exception var9) {
                this.logger.error("Release lock failed", var9);
                var5 = false;
            } finally {
                if (jedis != null) {
                    jedis.close();
                }
    
            }
    
            return var5;
        }

依赖

<dependency>
    			<groupId>redis.clients</groupId>
    			<artifactId>jedis</artifactId>
    		</dependency>

[http_doc.redisfans.com_script_eval.html]: http://doc.redisfans.com/script/eval.html
[https_blog.csdn.net_qq_39736103_article_details_116452752_utm_medium_distribute.pc_relevant.none-task-blog-baidujs_title-0_spm_1001.2101.3001.4242]: https://blog.csdn.net/qq_39736103/article/details/116452752?utm_medium=distribute.pc_relevant.none-task-blog-baidujs_title-0&spm=1001.2101.3001.4242