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Contents
# encoding: UTF-8
module Vines
# 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.
class TokenBucket
# Create a full bucket with capacity number of tokens to be filled
# at the given rate of tokens/second.
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
# Returns true if tokens can be taken from the bucket.
def take(tokens)
raise ArgumentError.new('tokens must be > 0') unless tokens > 0
if tokens <= fill
@tokens -= tokens
true
else
false
end
end
private
def fill
if @tokens < @capacity
now = Time.new
delta = (@rate * (now - @timestamp)).round
@tokens = [@capacity, @tokens + delta].min
@timestamp = now
end
@tokens
end
end
end
Version data entries
13 entries across 13 versions & 1 rubygems