cute-rate-limit

A cute rate limiter in Crystal that implements token bucket algorithm. Uses sleep blocking strategy when limit is exceeded.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     cute-rate-limit:
       github: BlossomiShymae/cute-rate-limit

2. Run shards install

Usage

require "cute-rate-limit"

A limiter uses a token bucket based algorithm that defaults to blocking strategy sleep when limit is exceeded.

In an example web API context, the limit is 20 requests every 1 second. It would be very, very bad if we ignore this limit. :c

Rate limiters solve this problem. Using a limiter with a full bucket, the maximum burst is 20 requests before limiter blocks with sleep. Tokens are allocated every 1 / token_rate period, where token_rate = bucket_size / bucket_period per second.

To create a limiter with a bucket_size of 20 tokens and a bucket_period of 1000 milliseconds:

cute_limiter = CuteRateLimit::Limiter.new 20 1*1000

For verbose readability:

cute_limiter = CuteRateLimit::Limiter.new 20 1.second.total_milliseconds.to_i

To use a limiter:

cute_limiter.use # => 19

Multiple limiters can be used together in tandem:

cute_limiter1 = CuteRateLimit::Limiter.new 20 1*1000
cute_limiter2 = CuteRateLimit::Limiter.new 100 120*1000

cute_limiter1.use
cute_limiter2.use

Check the bucket of a limiter with #token_bucket

cute_limiter2.token_bucket # => 100

50.times do
   cute_limiter2.use
end

cute_limiter2.token_bucket # => 50

Contributing

1. Fork it (https://github.com/BlossomiShymae/cute-rate-limit/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• BlossomiShymae - creator and maintainer