speed_limiter

SpeedLimiter

SpeedLimiter is a gem that limits the number of executions per unit of time. By default, it achieves throttling through sleep.

You can also use the on_throttled event to raise an exception instead of sleeping, or to re-enqueue the task.

Installation

Add this line to your application's Gemfile:

gem 'speed_limiter'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install speed_limiter

Usage

Limit the number of executions to 10 times per second.

SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1) do |state|
  puts state #=> <SpeedLimiter::State key=server_name/method_name count=1 ttl=0>
  http.get(path)
end

# or

throttle_limit_10_par_sec = SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1)

throttle_limit_10_par_sec.call do |state|
  puts state #=> <SpeedLimiter::State key=server_name/method_name count=1 ttl=0>
  http.get(path)
end

It returns the result of the block execution.

result = SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1) do
  http.get(path)
end
puts result.code #=> 200

on_throttled option

Specify the process when the limit is exceeded.

on_throttled = proc { |state| logger.info("limit exceeded #{state.key} #{state.ttl}") }
SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1, on_throttled: on_throttled) do
  http.get(path)
end

raise_on_throttled option

It raises an exception when the limit is exceeded.

begin
  SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1, raise_on_throttled: true) do
    http.get(path)
  end
rescue SpeedLimiter::ThrottledError => e
  logger.info(e.message) #=> "server_name/method_name rate limit exceeded. Retry after 0.9 seconds. limit=10, count=11, period=1"
  e.state #=> <SpeedLimiter::State key=server_name/method_name count=11 ttl=0.9>
end

Reinitialize the queue instead of sleeping when the limit is reached in ActiveJob.

class CreateSlackChannelJob < ApplicationJob
  rescue_from(SpeedLimiter::ThrottledError) do |e|
    Rails.logger.warn("[#{e.class}] #{self.class} retry job. #{e.message}")
    retry_job(wait: e.ttl, queue: 'low')
  end

  def perform(*args)
    SpeedLimiter.throttle("slack", limit: 20, period: 1.minute, raise_on_throttled: true) do
      create_slack_channel(*args)
    end
  end
end

retry option

To use the retry: option, you need to introduce the Retryable gem. By specifying the options of the Retryable gem, you can retry when an exception occurs.

# Gemfile
gem 'retryable'

SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1, retry: { tries: 3, on: OpenURI::HTTPError }) do
  http.get(path)
end

# equivalent to
SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1) do
  Retryable.retryable(tries: 3, on: OpenURI::HTTPError) do
    http.get(path)
  end
end

retry: true or retry: {} is default use of Retryable.configure.

SpeedLimiter.throttle('server_name/method_name', limit: 10, period: 1, retry: true) do
  http.get(path)
end

Configuration

Redis configuration

Redis can be specified as follows

1. default url redis://localhost:6379/0
2. SPEED_LIMITER_REDIS_URL environment variable
3. Configure SpeedLimiter.configure

# config/initializers/speed_limiter.rb
SpeedLimiter.configure do |config|
  config.redis_url = ENV.fetch('SPEED_LIMITER_REDIS_URL', 'redis://localhost:6379/2')
end

or Use Redis instance

# config/initializers/speed_limiter.rb
SpeedLimiter.configure do |config|
  config.redis = Redis.new(host: 'localhost', port: 6379, db: 2)
end

Other configuration defaults

SpeedLimiter.configure do |config|
   config.redis_url = ENV.fetch("SPEED_LIMITER_REDIS_URL", "redis://localhost:6379/0")
   config.redis = nil
   config.no_limit = false # If true, it will not be throttled
   config.prefix = "speed_limiter" # Redis key prefix
   config.on_throttled = nil # Proc to be executed when the limit is exceeded
end

Example

If you do not want to impose a limit in the test environment, please set it as follows.

# spec/support/speed_limiter.rb
RSpec.configure do |config|
  config.before(:suite) do
    SpeedLimiter.configure do |config|
      config.no_limit = true
    end
  end
end

If you want to detect the limit in the test environment, please set it as follows.

Rspec.describe do
  around do |example|
    SpeedLimiter.config.on_throttled = proc { |state| raise "limit exceeded #{state.key} #{state.ttl}" }

    example.run

    SpeedLimiter.config.on_throttled = nil
  end

  it do
    expect { over_limit_method }.to raise_error('limit exceeded key_name [\d.]+')
  end
end

Compatibility

SpeedLimiter officially supports the following Ruby implementations and Redis :

• Ruby MRI 3.0, 3.1, 3.2
• Redis 5.0, 6.0, 6.2, 7.0, 7.2

Development

After checking out the repo, run bin/setup to install dependencies. Please run rspec referring to the following.

Before committing, run bundle exec rubocop to perform a style check. You can also run bin/console for an interactive prompt that will allow you to experiment.

rspec

Start a test web server and Redis for testing with the following command.

$ rake throttle_server:start_daemon # or rake throttle_server:start
$ docker compose up -d

After that, please run the test with the following command.

$ bundle exec rspec -fd

Contribution

1. Fork it ( https://github.com/seibii/speed_limiter/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 new Pull Request

License

The gem is available as open source under the terms of the MIT License.