Redisson 分布式限流器 RRateLimiter 的使用及原理 - ToB企服应用市场:ToB评测及商务社交产业平台

/**
* Returns rate limiter instance by name
*
* @param name of rate limiter
* @return RateLimiter object
*/
RRateLimiter getRateLimiter(String name);

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/**
* Initializes RateLimiter's state and stores config to Redis server.
*
* @param mode - rate mode
* @param rate - rate
* @param rateInterval - rate time interval
* @param rateIntervalUnit - rate time interval unit
* @return true if rate was set and false otherwise
*/
boolean trySetRate(RateType mode, long rate, long rateInterval, RateIntervalUnit rateIntervalUnit);

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/**
* Acquires a specified permits from this RateLimiter,
* blocking until one is available.
*
* Acquires the given number of permits, if they are available
* and returns immediately, reducing the number of available permits
* by the given amount.
*
* @param permits the number of permits to acquire
*/
void acquire(long permits);
/**
* Acquires the given number of permits only if all are available
* within the given waiting time.
*
* Acquires the given number of permits, if all are available and returns immediately,
* with the value true, reducing the number of available permits by one.
*
* If no permit is available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until
* the specified waiting time elapses.
*
* If a permits is acquired then the value true is returned.
*
* If the specified waiting time elapses then the value false
* is returned. If the time is less than or equal to zero, the method
* will not wait at all.
*
* @param permits amount
* @param timeout the maximum time to wait for a permit
* @param unit the time unit of the timeout argument
* @return true if a permit was acquired and false
* if the waiting time elapsed before a permit was acquired
*/
boolean tryAcquire(long permits, long timeout, TimeUnit unit);

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@Slf4j
@SpringBootTest
class RateLimiterTest {
@Autowired
private RedissonClient redissonClient;
private static final int threadCount = 10;
@Test
void test() throws InterruptedException {
RRateLimiter rateLimiter = redissonClient.getRateLimiter("my_limiter");
rateLimiter.trySetRate(RateType.OVERALL, 10, 1, RateIntervalUnit.SECONDS);
CountDownLatch latch = new CountDownLatch(threadCount);
for (int i = 0; i < threadCount; i++) {
new Thread(() -> {
rateLimiter.tryAcquire(5, 3, TimeUnit.SECONDS);
latch.countDown();
log.info("latch count {}", latch.getCount());
}).start();
}
latch.await();
}
}

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2024-01-16 20:14:27 INFO [Thread-2] atreus.ink.rate.RateLimiterTest : latch count 9
2024-01-16 20:14:27 INFO [Thread-3] atreus.ink.rate.RateLimiterTest : latch count 8
2024-01-16 20:14:28 INFO [Thread-1] atreus.ink.rate.RateLimiterTest : latch count 7
2024-01-16 20:14:29 INFO [Thread-10] atreus.ink.rate.RateLimiterTest : latch count 6
2024-01-16 20:14:29 INFO [Thread-8] atreus.ink.rate.RateLimiterTest : latch count 5
2024-01-16 20:14:30 INFO [Thread-5] atreus.ink.rate.RateLimiterTest : latch count 4
2024-01-16 20:14:30 INFO [Thread-4] atreus.ink.rate.RateLimiterTest : latch count 3
2024-01-16 20:14:30 INFO [Thread-6] atreus.ink.rate.RateLimiterTest : latch count 2
2024-01-16 20:14:30 INFO [Thread-7] atreus.ink.rate.RateLimiterTest : latch count 1
2024-01-16 20:14:30 INFO [Thread-9] atreus.ink.rate.RateLimiterTest : latch count 0

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redis.call('hsetnx', KEYS[1], 'rate', ARGV[1]);
redis.call('hsetnx', KEYS[1], 'interval', ARGV[2]);
return redis.call('hsetnx', KEYS[1], 'type', ARGV[3]);

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-- 请求参数示例
-- KEYS[1] my_limiter
-- KEYS[2] {my_limiter}:value
-- KEYS[4] {my_limiter}:permits
-- ARGV[1] 3 本次请求的令牌数
-- ARGV[2] 1705396021850 System.currentTimeMillis()
-- ARGV[3] 6966135962453115904 ThreadLocalRandom.current().nextLong()
-- 读取 RRateLimiter.trySetRate 中配置的限流器信息
local rate = redis.call('hget', KEYS[1], 'rate'); -- 10 一个时间窗口内产生的令牌数
local interval = redis.call('hget', KEYS[1], 'interval'); -- 1000 一个时间窗口对应的毫秒数
local type = redis.call('hget', KEYS[1], 'type'); -- 0 全局限流
assert(rate ~= false and interval ~= false and type ~= false, 'RateLimiter is not initialized')
local valueName = KEYS[2]; -- {my_limiter}:value 当前可用令牌数字符串的 key
local permitsName = KEYS[4]; -- {my_limiter}:permits 授权记录有序集合的 key
-- 单机限流配置无需考虑
if type == '1' then
valueName = KEYS[3];
permitsName = KEYS[5];
end;
-- 查询当前可用的令牌数查询失败表明是首次请求令牌
local currentValue = redis.call('get', valueName);
if currentValue == false then -- 首次请求令牌
-- 单次请求的令牌数不能超过一个时间窗口内产生的令牌数
assert(tonumber(rate) >= tonumber(ARGV[1]), 'Requested permits amount could not exceed defined rate');
-- 更新当前可用令牌数以及令牌授权记录 {my_limiter}:permits
-- set {my_limiter}:permits 10
redis.call('set', valueName, rate);
-- zadd {my_limiter}:permits 1705396021850 6966135962453115904_1
redis.call('zadd', permitsName, ARGV[2], struct.pack('fI', ARGV[3], ARGV[1]));
-- decrby {my_limiter}:permits 3
redis.call('decrby', valueName, ARGV[1]);
return nil;
else -- 再次请求令牌
-- 查询可以回收的令牌对应的授权记录即一个时间窗口前的所有授权记录且包括一个时间窗口前这一时刻
-- 旧令牌回收的本质是新令牌的加入如果一个令牌是在一个时间窗口前被分配的那经过一个时间窗口后这个空出的位置应该已经由新令牌填充
-- zrangebyscore {my_limiter}:permits 0 1705396020850
local expiredValues = redis.call('zrangebyscore', permitsName, 0, tonumber(ARGV[2]) - interval); -- [1936135962853113704_2, 536135765023123704_5]
-- 统计可以回收的令牌数
local released = 0;
for i, v in ipairs(expiredValues) do
local random, permits = struct.unpack('fI', v);
-- released = released + 2
-- released = released + 5
released = released + permits;
end;
-- 删除授权记录并回收令牌
if released > 0 then
-- zrem {my_limiter}:permits 1936135962853113704_2 536135765023123704_5
redis.call('zrem', permitsName, unpack(expiredValues));
currentValue = tonumber(currentValue) + released;
-- incrby {my_limiter}:value 7
redis.call('set', valueName, currentValue);
end;
if tonumber(currentValue) < tonumber(ARGV[1]) then
-- 如果回收后可用令牌数仍然不足返回需要等待的时间
-- zrangebyscore {my_limiter}:permits (1705396020850 1705396021850 withscores limit 0 1
local nearest = redis.call('zrangebyscore', permitsName, '(' .. (tonumber(ARGV[2]) - interval), tonumber(ARGV[2]), 'withscores', 'limit', 0, 1);
local random, permits = struct.unpack('fI', nearest[1]);
-- 1705396021650 - 1705396021850 + 1000 = 800
return tonumber(nearest[2]) - (tonumber(ARGV[2]) - interval);
else
redis.call('zadd', permitsName, ARGV[2], struct.pack('fI', ARGV[3], ARGV[1]));
redis.call('decrby', valueName, ARGV[1]);
return nil;
end;
end;

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