How to implement current limiting in redis

Redis implements current limiting and uses the token bucket algorithm and sliding window algorithm. The token bucket algorithm limits incoming requests, and the sliding window algorithm records the number of requests within a certain period of time and determines whether it exceeds the threshold. Redis uses the incr/decr command to operate the token bucket, and uses the time and incrby commands to record the number of sliding window requests. Current limiting configuration is implemented through the set and config set commands. The sample code sets the token bucket capacity and rate, sliding window size and threshold, and checks whether the request is current limited.

Redis current limiting implementation

Redis uses the token bucket algorithm and Sliding window algorithm to achieve current limiting.

Token Bucket Algorithm

The Token Bucket Algorithm treats the requests flowing into the system as water flow, and the Token Bucket is a bucket that can hold a fixed number of tokens. container. The system adds tokens to the token bucket at a constant rate. When a request arrives, the system takes a token from the token bucket. If there are not enough tokens, the request is rejected.

Sliding window algorithm

The sliding window algorithm divides time into fixed-size intervals (windows) and records the number of requests within each window. When a new request arrives, the system checks whether the number of requests within the current window exceeds the threshold. If so, the request will be rejected.

Implementation in Redis

Redis uses a combination of token bucket algorithm and sliding window algorithm to achieve current limiting.

Token Bucket

The token bucket in Redis is operated using the incr/decr command. The incr command adds tokens to the token bucket, and the decr command removes tokens from the token bucket.

Sliding Window

Redis uses the time command to get the current time, and the incrby command to record each window number of requests within.

Current limiting configuration

Redis uses the set and config set commands to configure the current limiting parameters.

• set command is used to set the capacity and generation rate of the token bucket.
• config set command is used to set the size and threshold of the sliding window.

Usage Example

<code># 设置令牌桶，容量为100，生成速率为每秒10个令牌
SET my_token_bucket 100
CONFIG SET my_token_bucket_refill_rate 10

# 设置滑动窗口，大小为10秒，阈值为每秒100个请求
CONFIG SET my_sliding_window_size 10
CONFIG SET my_sliding_window_threshold 100

# 检查请求是否被限流
IF INCR my_sliding_window_counter > my_sliding_window_threshold THEN
  # 请求被限流，拒绝
  DECR my_sliding_window_counter
  RETURN -1
END IF

# 请求未被限流，记录请求并执行操作
INCR my_sliding_window_counter
# ... 执行操作 ...</code>

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