Sha256: bea45b2811b1a736b8abd98c7815d1799cc94a5de38fcead640828b137c7f936
Contents?: true
Size: 1.79 KB
Versions: 25
Compression:
Stored size: 1.79 KB
Contents
# encoding: utf-8
# This file is distributed under New Relic's license terms.
# See https://github.com/newrelic/rpm/blob/master/LICENSE for complete details.
# This class acts like an Array with a fixed capacity that randomly samples
# from a stream of items such that the probability of each item being included
# in the Array is equal. It uses reservoir sampling in order to achieve this:
# http://xlinux.nist.gov/dads/HTML/reservoirSampling.html
module NewRelic
module Agent
class SampledBuffer
attr_reader :seen, :capacity, :seen_lifetime, :captured_lifetime
def initialize(capacity)
@items = []
@capacity = capacity
@captured_lifetime = 0
@seen = 0
@seen_lifetime = 0
end
def reset
@captured_lifetime += @items.size
@seen_lifetime += @seen
@items = []
@seen = 0
end
def full?
@items.size >= @capacity
end
# Like '<<', but returns the value of full?
def append(x)
(self << x).full?
end
def <<(x)
@seen += 1
if @items.size < @capacity
@items << x
else
m = rand(@seen) # [0, @seen)
if m < @capacity
@items[m] = x
else
# discard current sample
end
end
return self
end
def size
@items.size
end
def to_a
@items.dup
end
def capacity=(new_capacity)
@capacity = new_capacity
old_items = @items
@items = []
old_items.each { |i| self << i }
end
def sample_rate
@seen > 0 ? (size.to_f / @seen) : 0.0
end
def sample_rate_lifetime
@captured_lifetime > 0 ? (@captured_lifetime.to_f / @seen_lifetime) : 0.0
end
end
end
end
Version data entries
25 entries across 25 versions & 1 rubygems