module TrafficJam

Constants

SimpleLimit

GCRA (Generic Cell Rate Algorithm) is a leaky bucket type rate limiting algorithm. GCRA works by storing a key in Redis with a ms-precision expiry representing the time that the limit will be completely reset. Each increment operation converts the increment amount into the number of milliseconds to be added to the expiry.

When a request comes in, we take the existing expiry value, subtract a fixed amount representing the limit’s total burst capacity from it, and compare the result to the current time. This result represents the next time to allow a request. If it’s in the past, we allow the incoming request, and if it’s in the future, we don’t. After a successful request, a new expiry is calculated. (see brandur.org/rate-limiting)

This limit type does not support decrements or changing the max value without a complete reset. This means that if the period or max value for an action/value key changes, the used and remaining values cannot be preserved.

Example: Limit is 5 per 10 seconds.

An increment by 1 first sets the key to expire in 2s.
Another immediate increment by 4 sets the expiry to 10s.
Subsequent increments fail until clock time catches up to expiry

Attributes

config[R]

Public Class Methods

configure() { |config| ... } click to toggle source

Configure library in a block.

@yield [TrafficJam::Configuration]

# File lib/traffic_jam.rb, line 25
def configure
  yield config
end

limit(action, value) click to toggle source

Create limit with registed max/period.

@param action [Symbol] registered action name @param value [String] limit target value @return [TrafficJam::Limit]

# File lib/traffic_jam.rb, line 34
def limit(action, value)
  limits = config.limits(action.to_sym)
  TrafficJam::Limit.new(action, value, **limits)
end

reset_all(action: nil) click to toggle source

Reset all limits associated with the given action. If action is omitted or nil, this will reset all limits.

@note Not recommended for use in production. @param action [Symbol] action to reset limits for @return [nil]

# File lib/traffic_jam.rb, line 45
def reset_all(action: nil)
  prefix =
    if action.nil?
      "#{config.key_prefix}:*"
    else
      "#{config.key_prefix}:#{action}:*"
    end
  config.redis.keys(prefix).each do |key|
    config.redis.del(key)
  end
  nil
end