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# frozen_string_literal: true
# rubocop:todo all
# Copyright (C) 2018-2020 MongoDB Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
module Mongo
class Server
# @api private
class RoundTripTimeCalculator
# The weighting factor (alpha) for calculating the average moving
# round trip time.
RTT_WEIGHT_FACTOR = 0.2.freeze
private_constant :RTT_WEIGHT_FACTOR
RTT_SAMPLES_FOR_MINIMUM = 10
private_constant :RTT_SAMPLES_FOR_MINIMUM
MIN_SAMPLES = 3
private_constant :MIN_SAMPLES
def initialize
@last_round_trip_time = nil
@average_round_trip_time = nil
@minimum_round_trip_time = 0
@lock = Mutex.new
@rtts = []
end
attr_reader :last_round_trip_time
attr_reader :average_round_trip_time
attr_reader :minimum_round_trip_time
def measure
start = Utils.monotonic_time
begin
rv = yield
rescue Error::SocketError, Error::SocketTimeoutError
# If we encountered a network error, the round-trip is not
# complete and thus RTT for it does not make sense.
raise
rescue Error, Error::AuthError => exc
# For other errors, RTT is valid.
end
last_rtt = Utils.monotonic_time - start
# If hello fails, we need to return the last round trip time
# because it is used in the heartbeat failed SDAM event,
# but we must not update the round trip time recorded in the server.
unless exc
@last_round_trip_time = last_rtt
@lock.synchronize do
update_average_round_trip_time
update_minimum_round_trip_time
end
end
if exc
raise exc
else
rv
end
end
def update_average_round_trip_time
@average_round_trip_time = if average_round_trip_time
RTT_WEIGHT_FACTOR * last_round_trip_time + (1 - RTT_WEIGHT_FACTOR) * average_round_trip_time
else
last_round_trip_time
end
end
def update_minimum_round_trip_time
@rtts.push(last_round_trip_time) unless last_round_trip_time.nil?
@minimum_round_trip_time = 0 and return if @rtts.size < MIN_SAMPLES
@rtts.shift if @rtts.size > RTT_SAMPLES_FOR_MINIMUM
@minimum_round_trip_time = @rtts.compact.min
end
end
end
end
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