分布式限流——Redis实现令牌桶算法

import redis
import time
import random
 
# 连接Redis
r = redis.Redis(host='localhost', port=6379, db=0)
 
# 令牌桶算法实现分布式限流
class RateLimiter(object):
    def __init__(self, rate, burst=10):
        self.rate = rate
        self.burst = burst
        self.tokens_key = 'tokens'
        self.timestamp_key = 'timestamp'
        self.fill_rate = rate / burst
 
    def _get_tokens(self):
        timestamp = r.get(self.timestamp_key)
        if timestamp is None:
            r.set(self.tokens_key, self.burst)
            r.set(self.timestamp_key, time.time())
            return self.burst
        else:
            tokens = r.get(self.tokens_key)
            if tokens is None:
                r.set(self.tokens_key, self.burst)
                r.set(self.timestamp_key, time.time())
                return self.burst
            else:
                return int(tokens)
 
    def _reduce_tokens(self, cost):
        tokens = self._get_tokens()
        if tokens >= cost:
            r.decrby(self.tokens_key, cost)
            return True
        else:
            return False
 
    def _fill_token(self):
        timestamp = r.get(self.timestamp_key)
        if timestamp is not None:
            elapsed = time.time() - float(timestamp)
            if elapsed > 0:
                time_to_wait = self.fill_rate * elapsed
                time.sleep(time_to_wait)
                r.incrbyfloat(self.tokens_key, self.fill_rate * elapsed)
                r.set(self.timestamp_key, time.time())
 
    def allowed(self, cost=1):
        self._fill_token()
        return self._reduce_tokens(cost)
 
# 使用示例
limiter = RateLimiter(rate=5, burst=10)  # 每秒5个请求，初始令牌桶容量10
 
# 模拟请求
for i in range(20):
    if limiter.allowed():
        print(f"Request {i} is allowed!")
        time.sleep(random.uniform(0, 1))  # 模拟请求处理时间
    else:
        print(f"Request {i} is denied!")

这段代码实现了基于Redis的令牌桶算法分布式限流器。它首先连接到Redis，然后定义了一个RateLimiter类，用于初始化限流器并实现相关的方法。allowed方法检查是否有足够的令牌来处理请求，如果有，则处理请求并减少令牌数量；如果没有，则拒绝请求。代码还包括了令牌填充的逻辑，确保在超出 burst 限制后能够按照固定的速率进行令牌填充。最后，提供了使用限流器的模拟请求示例。