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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
require 'new_relic/agent/event_buffer'
module NewRelic
module Agent
class SampledBuffer < EventBuffer
attr_reader :seen_lifetime, :captured_lifetime
def initialize(capacity)
super
@captured_lifetime = 0
@seen_lifetime = 0
end
def reset!
@captured_lifetime += @items.size
@seen_lifetime += @seen
super
end
def append_event(x)
if @items.size < @capacity
@items << x
return x
else
m = rand(@seen) # [0, @seen)
if m < @capacity
@items[m] = x
return x
else
# discard current sample
return nil
end
end
end
def sample_rate_lifetime
@captured_lifetime > 0 ? (@captured_lifetime.to_f / @seen_lifetime) : 0.0
end
end
end
end
Version data entries
12 entries across 12 versions & 1 rubygems