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# Copyright (C) 2014-2017 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.
require 'mongo/server/monitor/connection'
module Mongo
class Server
# This object is responsible for keeping server status up to date, running in
# a separate thread as to not disrupt other operations.
#
# @since 2.0.0
class Monitor
include Loggable
extend Forwardable
# The default time for a server to refresh its status is 10 seconds.
#
# @since 2.0.0
HEARTBEAT_FREQUENCY = 10.freeze
# The minimum time between forced server scans. Is
# minHeartbeatFrequencyMS in the SDAM spec.
#
# @since 2.0.0
MIN_SCAN_FREQUENCY = 0.5.freeze
# The weighting factor (alpha) for calculating the average moving round trip time.
#
# @since 2.0.0
RTT_WEIGHT_FACTOR = 0.2.freeze
# @return [ Mongo::Connection ] connection The connection to use.
attr_reader :connection
# @return [ Server::Description ] description The server
# description the monitor refreshes.
attr_reader :description
# @return [ Description::Inspector ] inspector The description inspector.
attr_reader :inspector
# @return [ Hash ] options The server options.
attr_reader :options
# @return [ Time ] last_scan The time of the last server scan.
#
# @since 2.4.0
attr_reader :last_scan
# The compressor is determined during the handshake, so it must be an attribute
# of the connection.
def_delegators :connection, :compressor
# Force the monitor to immediately do a check of its server.
#
# @example Force a scan.
# monitor.scan!
#
# @return [ Description ] The updated description.
#
# @since 2.0.0
def scan!
throttle_scan_frequency!
@description = inspector.run(description, *ismaster)
end
# Get the refresh interval for the server. This will be defined via an option
# or will default to 5.
#
# @example Get the refresh interval.
# server.heartbeat_frequency
#
# @return [ Integer ] The heartbeat frequency, in seconds.
#
# @since 2.0.0
def heartbeat_frequency
@heartbeat_frequency ||= options[:heartbeat_frequency] || HEARTBEAT_FREQUENCY
end
# Create the new server monitor.
#
# @api private
#
# @example Create the server monitor.
# Mongo::Server::Monitor.new(address, listeners)
#
# @note Monitor must never be directly instantiated outside of a Server.
#
# @param [ Address ] address The address to monitor.
# @param [ Event::Listeners ] listeners The event listeners.
# @param [ Hash ] options The options.
#
# @since 2.0.0
def initialize(address, listeners, options = {})
@description = Description.new(address, {})
@inspector = Description::Inspector.new(listeners)
@options = options.freeze
@connection = Connection.new(address, options)
@last_round_trip_time = nil
@last_scan = nil
@mutex = Mutex.new
end
# Runs the server monitor. Refreshing happens on a separate thread per
# server.
#
# @example Run the monitor.
# monitor.run
#
# @return [ Thread ] The thread the monitor runs on.
#
# @since 2.0.0
def run!
@thread = Thread.new(heartbeat_frequency) do |i|
loop do
sleep(i)
scan!
end
end
end
# Stops the server monitor. Kills the thread so it doesn't continue
# taking memory and sending commands to the connection.
#
# @example Stop the monitor.
# monitor.stop!
#
# @return [ Boolean ] Is the Thread stopped?
#
# @since 2.0.0
def stop!
connection.disconnect! && @thread.kill && @thread.stop?
end
# Restarts the server monitor unless the current thread is alive.
#
# @example Restart the monitor.
# monitor.restart!
#
# @return [ Thread ] The thread the monitor runs on.
#
# @since 2.1.0
def restart!
@thread.alive? ? @thread : run!
end
private
def average_round_trip_time(start)
new_rtt = Time.now - start
RTT_WEIGHT_FACTOR * new_rtt + (1 - RTT_WEIGHT_FACTOR) * (@last_round_trip_time || new_rtt)
end
def calculate_average_round_trip_time(start)
@last_round_trip_time = average_round_trip_time(start)
end
def ismaster
@mutex.synchronize do
start = Time.now
begin
return connection.ismaster, calculate_average_round_trip_time(start)
rescue Exception => e
log_debug(e.message)
return {}, calculate_average_round_trip_time(start)
end
end
end
def throttle_scan_frequency!
if @last_scan
difference = (Time.now - @last_scan)
throttle_time = (MIN_SCAN_FREQUENCY - difference)
sleep(throttle_time) if throttle_time > 0
end
@last_scan = Time.now
end
end
end
end
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