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# frozen_string_literal: true
module Sentry
module Utils
class SampleRand
PRECISION = 1_000_000.0
FORMAT_PRECISION = 6
attr_reader :trace_id
def self.valid?(value)
return false unless value
value >= 0.0 && value < 1.0
end
def self.format(value)
return unless value
truncated = (value * PRECISION).floor / PRECISION
"%.#{FORMAT_PRECISION}f" % truncated
end
def initialize(trace_id: nil)
@trace_id = trace_id
end
def generate_from_trace_id
(random_from_trace_id * PRECISION).floor / PRECISION
end
def generate_from_sampling_decision(sampled, sample_rate)
if invalid_sample_rate?(sample_rate)
fallback_generation
else
generate_based_on_sampling(sampled, sample_rate)
end
end
def generate_from_value(sample_rand_value)
parsed_value = parse_value(sample_rand_value)
if self.class.valid?(parsed_value)
parsed_value
else
fallback_generation
end
end
private
def random_from_trace_id
if @trace_id
Random.new(@trace_id[0, 16].to_i(16))
else
Random.new
end.rand(1.0)
end
def invalid_sample_rate?(sample_rate)
sample_rate.nil? || sample_rate <= 0.0 || sample_rate > 1.0
end
def fallback_generation
if @trace_id
(random_from_trace_id * PRECISION).floor / PRECISION
else
format_random(Random.rand(1.0))
end
end
def generate_based_on_sampling(sampled, sample_rate)
random = random_from_trace_id
result = if sampled
random * sample_rate
elsif sample_rate == 1.0
random
else
sample_rate + random * (1.0 - sample_rate)
end
format_random(result)
end
def format_random(value)
truncated = (value * PRECISION).floor / PRECISION
("%.#{FORMAT_PRECISION}f" % truncated).to_f
end
def parse_value(sample_rand_value)
Float(sample_rand_value)
rescue ArgumentError
nil
end
end
end
end
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