Class: Vines::TokenBucket

Inherits:
Object
  • Object
show all
Defined in:
lib/vines/token_bucket.rb

Overview

The token bucket algorithm is useful for rate limiting. Before an operation can be completed, a token is taken from the bucket. If no tokens are available, the operation fails. The bucket is refilled with tokens at the maximum allowed rate of operations.

Instance Method Summary collapse

Constructor Details

#initialize(capacity, rate) ⇒ TokenBucket

Create a full bucket with ‘capacity` number of tokens to be filled at the given rate of tokens/second.

capacity - The Fixnum maximum number of tokens the bucket can hold. rate - The Fixnum number of tokens per second at which the bucket is

refilled.

Raises:

  • (ArgumentError) 


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# File 'lib/vines/token_bucket.rb', line 18

def initialize(capacity, rate)
  raise ArgumentError.new('capacity must be > 0') unless capacity > 0
  raise ArgumentError.new('rate must be > 0') unless rate > 0
  @capacity = capacity
  @tokens = capacity
  @rate = rate
  @timestamp = Time.new
end

Instance Method Details

#take(tokens) ⇒ Object

Remove tokens from the bucket if it’s full enough. There’s no way, or need, to add tokens to the bucket. It refills over time.

tokens - The Fixnum number of tokens to attempt to take from the bucket.

Returns true if the bucket contains enough tokens to take, false if the bucket isn’t full enough to satisy the request.

Raises:

  • (ArgumentError) 


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# File 'lib/vines/token_bucket.rb', line 34

def take(tokens)
  raise ArgumentError.new('tokens must be > 0') unless tokens > 0
  tokens <= fill ? @tokens -= tokens : false
end