class Ratelimit

Constants

VERSION

Public Class Methods

new(key, options = {}) click to toggle source

Create a RateLimit object.

@param [String] key A name to uniquely identify this rate limit. For example, 'emails' @param [Hash] options Options hash @option options [Integer] :bucket_span (600) Time span to track in seconds @option options [Integer] :bucket_interval (5) How many seconds each bucket represents @option options [Integer] :bucket_expiry (@bucket_span) How long we keep data in each bucket before it is auto expired. Cannot be larger than the bucket_span. @option options [Redis] :redis (nil) Redis client if you need to customize connection options

@return [RateLimit] RateLimit instance

# File lib/ratelimit.rb, line 17
def initialize(key, options = {})
  @key = key
  unless options.is_a?(Hash)
    raise ArgumentError.new("Redis object is now passed in via the options hash - options[:redis]")
  end
  @bucket_span = options[:bucket_span] || 600
  @bucket_interval = options[:bucket_interval] || 5
  @bucket_expiry = options[:bucket_expiry] || @bucket_span
  if @bucket_expiry > @bucket_span
    raise ArgumentError.new("Bucket expiry cannot be larger than the bucket span")
  end
  @bucket_count = (@bucket_span / @bucket_interval).round
  if @bucket_count < 3
    raise ArgumentError.new("Cannot have less than 3 buckets")
  end
  @raw_redis = options[:redis]
end

Public Instance Methods

add(subject, count = 1) click to toggle source

Add to the counter for a given subject.

@param [String] subject A unique key to identify the subject. For example, 'user@foo.com' @param [Integer] count The number by which to increase the counter

@return [Integer] The counter value

# File lib/ratelimit.rb, line 41
def add(subject, count = 1)
  bucket = get_bucket
  subject = "#{@key}:#{subject}"
  redis.multi do
    redis.hincrby(subject, bucket, count)
    redis.hdel(subject, (bucket + 1) % @bucket_count)
    redis.hdel(subject, (bucket + 2) % @bucket_count)
    redis.expire(subject, @bucket_expiry)
  end.first
end

count(subject, interval) click to toggle source

Returns the count for a given subject and interval

@param [String] subject Subject for the count @param [Integer] interval How far back (in seconds) to retrieve activity.

# File lib/ratelimit.rb, line 56
def count(subject, interval)
  bucket = get_bucket
  interval = [[interval, @bucket_interval].max, @bucket_span].min
  count = (interval / @bucket_interval).floor
  subject = "#{@key}:#{subject}"

  keys = (0..count - 1).map do |i|
    (bucket - i) % @bucket_count
  end
  return redis.hmget(subject, *keys).inject(0) {|a, i| a + i.to_i}
end

exceeded?(subject, options = {}) click to toggle source

Check if the rate limit has been exceeded.

@param [String] subject Subject to check @param [Hash] options Options hash @option options [Integer] :interval How far back to retrieve activity. @option options [Integer] :threshold Maximum number of actions

# File lib/ratelimit.rb, line 74
def exceeded?(subject, options = {})
  return count(subject, options[:interval]) >= options[:threshold]
end

exec_within_threshold(subject, options = {}) { |self| ... } click to toggle source

Execute a block once the rate limit is within bounds WARNING This will block the current thread until the rate limit is within bounds.

@param [String] subject Subject for this rate limit @param [Hash] options Options hash @option options [Integer] :interval How far back to retrieve activity. @option options [Integer] :threshold Maximum number of actions @yield The block to be run

@example Send an email as long as we haven't send 5 in the last 10 minutes

ratelimit.exec_with_threshold(email, [:threshold => 5, :interval => 600]) do
  send_another_email
  ratelimit.add(email)
end

# File lib/ratelimit.rb, line 102
def exec_within_threshold(subject, options = {}, &block)
  options[:threshold] ||= 30
  options[:interval] ||= 30
  while exceeded?(subject, options)
    sleep @bucket_interval
  end
  yield(self)
end

within_bounds?(subject, options = {}) click to toggle source

Check if the rate limit is within bounds

# File lib/ratelimit.rb, line 84
def within_bounds?(subject, options = {})
  return !exceeded?(subject, options)
end

Private Instance Methods

get_bucket(time = Time.now.to_i) click to toggle source

# File lib/ratelimit.rb, line 113
def get_bucket(time = Time.now.to_i)
  ((time % @bucket_span) / @bucket_interval).floor
end

redis() click to toggle source

# File lib/ratelimit.rb, line 117
def redis
  @redis ||= Redis::Namespace.new(:ratelimit, redis: @raw_redis || Redis.new)
end