Class: Prop::LeakyBucketStrategy

Inherits:
Object
  • Object
show all
Defined in:
lib/prop/leaky_bucket_strategy.rb

Class Method Summary collapse

Class Method Details

.build(options) ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 38

def build(options)
  key       = options.fetch(:key)
  handle    = options.fetch(:handle)

  cache_key = Prop::Key.normalize([ handle, key ])

  "prop/leaky_bucket/#{Digest::MD5.hexdigest(cache_key)}"
end

.change(cache_key, options) ⇒ Object

WARNING: race condition this increment is not atomic, so it might miss counts when used frequently

Raises:

  • (ArgumentError) 


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# File 'lib/prop/leaky_bucket_strategy.rb', line 20

def change(cache_key, options)
  # please open a PR if you know how to support this
  raise ArgumentError, "decrement is not supported for LeakyBucketStrategy" if options.key?(:decrement)

  counter = counter(cache_key, options)
  counter[:bucket] += options.fetch(:increment, 1)
  Prop::Limiter.cache.write(cache_key, counter)
  counter
end

.compare_threshold?(counter, operator, options) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/prop/leaky_bucket_strategy.rb', line 34

def compare_threshold?(counter, operator, options)
  counter.fetch(:bucket).to_i.send operator, options.fetch(:burst_rate)
end

.counter(cache_key, options) ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 8

def counter(cache_key, options)
  bucket = Prop::Limiter.cache.read(cache_key) || zero_counter
  now = Time.now.to_i
  leak_amount = (now - bucket.fetch(:last_updated)) / options.fetch(:interval) * options.fetch(:threshold)

  bucket[:bucket] = [bucket.fetch(:bucket) - leak_amount, 0].max
  bucket[:last_updated] = now
  bucket
end

.reset(cache_key) ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 30

def reset(cache_key)
  Prop::Limiter.cache.write(cache_key, zero_counter)
end

.threshold_reached(options) ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 47

def threshold_reached(options)
  burst_rate = options.fetch(:burst_rate)
  threshold  = options.fetch(:threshold)

  "#{options[:handle]} threshold of #{threshold} tries per #{options[:interval]}s and burst rate #{burst_rate} tries exceeded for key #{options[:key].inspect}, hash #{options[:cache_key]}"
end

.validate_options!(options) ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 54

def validate_options!(options)
  Prop::IntervalStrategy.validate_options!(options)

  if !options[:burst_rate].is_a?(Fixnum) || options[:burst_rate] < options[:threshold]
    raise ArgumentError.new(":burst_rate must be an Integer and not less than :threshold")
  end

  if options[:first_throttled]
    raise ArgumentError.new(":first_throttled is not supported")
  end
end

.zero_counter ⇒ Object 



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# File 'lib/prop/leaky_bucket_strategy.rb', line 66

def zero_counter
  { bucket: 0, last_updated: 0 }
end