Redis中分布式限流的三种实现方案详解

local key = KEYS[1]
local limit = tonumber(ARGV[1])
local ttl = tonumber(ARGV[2])
-- 原子性自增
local current = redis.call('INCR', key)
-- 首次访问设置过期时间
if current == 1 then
    redis.call('EXPIRE', key, ttl)
end
return current

@Component
public class FixedWindowRateLimiter {
    private static final String LUA_SCRIPT = 
        "local current = redis.call('INCR', KEYS[1])\n" +
        "if current == 1 then\n" +
        "    redis.call('EXPIRE', KEYS[1], ARGV[2])\n" +
        "end\n" +
        "return current";
    public boolean allow(String key, int limit, int windowSeconds) {
        Long count = redisTemplate.execute(
            new DefaultRedisScript<>(LUA_SCRIPT, Long.class),
            Collections.singletonList(key),
            String.valueOf(limit),
            String.valueOf(windowSeconds)
        );
        return count != null && count <= limit;
    }
}

local key = KEYS[1]
local now = tonumber(ARGV[1])
local window = tonumber(ARGV[2])    -- 窗口大小（毫秒）
local limit = tonumber(ARGV[3])
-- 移除窗口外的旧数据
redis.call('ZREMRANGEBYSCORE', key, 0, now - window)
-- 获取当前窗口内的请求数
local count = redis.call('ZCARD', key)
if count >= limit then
    return count  -- 拦截
end
-- 添加当前请求（使用毫秒时间戳 + 随机数作为 member，避免重复）
redis.call('ZADD', key, now, now .. ':' .. math.random())
-- 设置过期时间（窗口 + 1 秒）
redis.call('PEXPIRE', key, window + 1000)
return 0  -- 放行

@Component
public class SlidingWindowRateLimiter {
    private static final String LUA_SCRIPT = 
        "local window = tonumber(ARGV[2])\n" +
        "local now = tonumber(ARGV[1])\n" +
        "local limit = tonumber(ARGV[3])\n" +
        "redis.call('ZREMRANGEBYSCORE', KEYS[1], 0, now - window)\n" +
        "local count = redis.call('ZCARD', KEYS[1])\n" +
        "if count >= limit then return count end\n" +
        "redis.call('ZADD', KEYS[1], now, now .. ':' .. math.random())\n" +
        "redis.call('PEXPIRE', KEYS[1], window + 1000)\n" +
        "return 0";
    public boolean allow(String key, int limit, int windowMs) {
        long now = System.currentTimeMillis();
        Long count = redisTemplate.execute(
            new DefaultRedisScript<>(LUA_SCRIPT, Long.class),
            Collections.singletonList(key),
            String.valueOf(now),
            String.valueOf(windowMs),
            String.valueOf(limit)
        );
        return count != null && count == 0;
    }
}

local key = KEYS[1]
local limit = tonumber(ARGV[1])      -- 桶容量
local rate = tonumber(ARGV[2])       -- 填充速率（令牌/秒）
local now = tonumber(ARGV[3])
-- 获取桶状态
local state = redis.call('HMGET', key, 'tokens', 'last_time')
local tokens = tonumber(state[1]) or limit
local lastTime = tonumber(state[2]) or now
-- 计算应该补充的令牌数
local delta = math.max(0, now - lastTime)
local filledTokens = math.min(limit, tokens + (delta * rate / 1000))
-- 判断是否有足够令牌
if filledTokens >= 1 then
    -- 消耗 1 个令牌
    local newTokens = filledTokens - 1
    redis.call('HMSET', key, 'tokens', newTokens, 'last_time', now)
    redis.call('EXPIRE', key, 10)
    return 1  -- 放行
else
    -- 更新状态（不消耗）
    redis.call('HMSET', key, 'tokens', filledTokens, 'last_time', now)
    redis.call('EXPIRE', key, 10)
    return 0  -- 拦截
end

@Component
public class TokenBucketRateLimiter {
    private static final String LUA_SCRIPT = 
        "local limit = tonumber(ARGV[1])\n" +
        "local rate = tonumber(ARGV[2])\n" +
        "local now = tonumber(ARGV[3])\n" +
        "local state = redis.call('HMGET', KEYS[1], 'tokens', 'last_time')\n" +
        "local tokens = tonumber(state[1]) or limit\n" +
        "local lastTime = tonumber(state[2]) or now\n" +
        "local delta = math.max(0, now - lastTime)\n" +
        "local filled = math.min(limit, tokens + (delta * rate / 1000))\n" +
        "if filled >= 1 then\n" +
        "    redis.call('HMSET', KEYS[1], 'tokens', filled - 1, 'last_time', now)\n" +
        "    redis.call('EXPIRE', KEYS[1], 10)\n" +
        "    return 1\n" +
        "end\n" +
        "redis.call('HMSET', KEYS[1], 'tokens', filled, 'last_time', now)\n" +
        "return 0";
    public boolean allow(String key, int capacity, int ratePerSecond) {
        long now = System.currentTimeMillis();
        Long result = redisTemplate.execute(
            new DefaultRedisScript<>(LUA_SCRIPT, Long.class),
            Collections.singletonList(key),
            String.valueOf(capacity),
            String.valueOf(ratePerSecond),
            String.valueOf(now)
        );
        return result != null && result == 1;
    }
}