# encoding: utf-8
# This file is distributed under New Relic's license terms.
# See https://github.com/newrelic/newrelic-ruby-agent/blob/main/LICENSE for complete details.
# frozen_string_literal: true

require 'socket'
require 'net/https'
require 'net/http'
require 'logger'
require 'zlib'
require 'stringio'
require 'new_relic/constants'
require 'new_relic/traced_thread'
require 'new_relic/coerce'
require 'new_relic/agent/autostart'
require 'new_relic/agent/harvester'
require 'new_relic/agent/hostname'
require 'new_relic/agent/new_relic_service'
require 'new_relic/agent/pipe_service'
require 'new_relic/agent/configuration/manager'
require 'new_relic/agent/database'
require 'new_relic/agent/instrumentation/resque/helper'
require 'new_relic/agent/commands/agent_command_router'
require 'new_relic/agent/event_listener'
require 'new_relic/agent/distributed_tracing'
require 'new_relic/agent/monitors'
require 'new_relic/agent/transaction_event_recorder'
require 'new_relic/agent/custom_event_aggregator'
require 'new_relic/agent/span_event_aggregator'
require 'new_relic/agent/log_event_aggregator'
require 'new_relic/agent/sampler_collection'
require 'new_relic/agent/javascript_instrumentor'
require 'new_relic/agent/vm/monotonic_gc_profiler'
require 'new_relic/agent/utilization_data'
require 'new_relic/environment_report'
require 'new_relic/agent/attribute_filter'
require 'new_relic/agent/adaptive_sampler'
require 'new_relic/agent/connect/request_builder'
require 'new_relic/agent/connect/response_handler'

require 'new_relic/agent/agent/start_worker_thread'
require 'new_relic/agent/agent/startup'
require 'new_relic/agent/agent/special_startup'
require 'new_relic/agent/agent/shutdown'

module NewRelic
  module Agent
    # The Agent is a singleton that is instantiated when the plugin is
    # activated.  It collects performance data from ruby applications
    # in realtime as the application runs, and periodically sends that
    # data to the NewRelic server.
    class Agent
      def self.config
        ::NewRelic::Agent.config
      end

      include NewRelic::Agent::StartWorkerThread
      include NewRelic::Agent::SpecialStartup
      include NewRelic::Agent::Startup
      include NewRelic::Agent::Shutdown

      def initialize
        @started = false
        @event_loop = nil
        @worker_thread = nil

        @service = NewRelicService.new

        @events = EventListener.new
        @stats_engine = StatsEngine.new
        @transaction_sampler = TransactionSampler.new
        @sql_sampler = SqlSampler.new
        @agent_command_router = Commands::AgentCommandRouter.new(@events)
        @monitors = Monitors.new(@events)
        @error_collector = ErrorCollector.new(@events)
        @transaction_rules = RulesEngine.new
        @harvest_samplers = SamplerCollection.new(@events)
        @monotonic_gc_profiler = VM::MonotonicGCProfiler.new
        @javascript_instrumentor = JavascriptInstrumentor.new(@events)
        @adaptive_sampler = AdaptiveSampler.new(Agent.config[:sampling_target],
          Agent.config[:sampling_target_period_in_seconds])

        @harvester = Harvester.new(@events)
        @after_fork_lock = Mutex.new

        @transaction_event_recorder = TransactionEventRecorder.new(@events)
        @custom_event_aggregator = CustomEventAggregator.new(@events)
        @span_event_aggregator = SpanEventAggregator.new(@events)
        @log_event_aggregator = LogEventAggregator.new(@events)

        @connect_state = :pending
        @connect_attempts = 0
        @waited_on_connect = nil
        @connected_pid = nil

        @wait_on_connect_mutex = Mutex.new
        @wait_on_connect_condition = ConditionVariable.new

        setup_attribute_filter
      end

      def setup_attribute_filter
        refresh_attribute_filter

        @events.subscribe(:initial_configuration_complete) do
          refresh_attribute_filter
        end
      end

      def refresh_attribute_filter
        @attribute_filter = AttributeFilter.new(Agent.config)
      end

      # contains all the class-level methods for NewRelic::Agent::Agent
      module ClassMethods
        # Should only be called by NewRelic::Control - returns a
        # memoized singleton instance of the agent, creating one if needed
        def instance
          @instance ||= self.new
        end
      end

      # Holds all the methods defined on NewRelic::Agent::Agent
      # instances
      module InstanceMethods
        # the statistics engine that holds all the timeslice data
        attr_reader :stats_engine
        # the transaction sampler that handles recording transactions
        attr_reader :transaction_sampler
        attr_reader :sql_sampler
        # manages agent commands we receive from the collector, and the handlers
        attr_reader :agent_command_router
        # error collector is a simple collection of recorded errors
        attr_reader :error_collector
        attr_reader :harvest_samplers
        # whether we should record raw, obfuscated, or no sql
        attr_reader :record_sql
        # builder for JS agent scripts to inject
        attr_reader :javascript_instrumentor
        # cross application tracing ids and encoding
        attr_reader :cross_process_id
        attr_reader :cross_app_encoding_bytes
        # service for communicating with collector
        attr_accessor :service
        # Global events dispatcher. This will provides our primary mechanism
        # for agent-wide events, such as finishing configuration, error notification
        # and request before/after from Rack.
        attr_reader :events

        # listens and responds to events that need to process headers
        # for synthetics and distributed tracing
        attr_reader :monitors
        # Transaction and metric renaming rules as provided by the
        # collector on connect.  The former are applied during txns,
        # the latter during harvest.
        attr_accessor :transaction_rules
        # Responsbile for restarting the harvest thread
        attr_reader :harvester
        # GC::Profiler.total_time is not monotonic so we wrap it.
        attr_reader :monotonic_gc_profiler
        attr_reader :custom_event_aggregator
        attr_reader :span_event_aggregator
        attr_reader :log_event_aggregator
        attr_reader :transaction_event_recorder
        attr_reader :attribute_filter
        attr_reader :adaptive_sampler
        attr_reader :environment_report

        def transaction_event_aggregator
          @transaction_event_recorder.transaction_event_aggregator
        end

        def synthetics_event_aggregator
          @transaction_event_recorder.synthetics_event_aggregator
        end

        def agent_id=(agent_id)
          @service.agent_id = agent_id
        end

        # This method should be called in a forked process after a fork.
        # It assumes the parent process initialized the agent, but does
        # not assume the agent started.
        #
        # The call is idempotent, but not re-entrant.
        #
        # * It clears any metrics carried over from the parent process
        # * Restarts the sampler thread if necessary
        # * Initiates a new agent run and worker loop unless that was done
        #   in the parent process and +:force_reconnect+ is not true
        #
        # Options:
        # * <tt>:force_reconnect => true</tt> to force the spawned process to
        #   establish a new connection, such as when forking a long running process.
        #   The default is false--it will only connect to the server if the parent
        #   had not connected.
        # * <tt>:keep_retrying => false</tt> if we try to initiate a new
        #   connection, this tells me to only try it once so this method returns
        #   quickly if there is some kind of latency with the server.
        def after_fork(options = {})
          needs_restart = false
          @after_fork_lock.synchronize do
            needs_restart = @harvester.needs_restart?
            @harvester.mark_started
          end

          return if !needs_restart ||
            !Agent.config[:agent_enabled] ||
            !Agent.config[:monitor_mode] ||
            disconnected? ||
            !control.security_settings_valid?

          ::NewRelic::Agent.logger.debug("Starting the worker thread in #{Process.pid} (parent #{Process.ppid}) after forking.")

          channel_id = options[:report_to_channel]
          install_pipe_service(channel_id) if channel_id

          # Clear out locks and stats left over from parent process
          reset_objects_with_locks
          drop_buffered_data

          setup_and_start_agent(options)
        end

        def install_pipe_service(channel_id)
          @service = PipeService.new(channel_id)
          if connected?
            @connected_pid = Process.pid
          else
            ::NewRelic::Agent.logger.debug("Child process #{Process.pid} not reporting to non-connected parent (process #{Process.ppid}).")
            @service.shutdown
            disconnect
          end
        end

        def revert_to_default_configuration
          Agent.config.remove_config_type(:manual)
          Agent.config.remove_config_type(:server)
        end

        def trap_signals_for_litespeed
          # if litespeed, then ignore all future SIGUSR1 - it's
          # litespeed trying to shut us down
          if Agent.config[:dispatcher] == :litespeed
            Signal.trap("SIGUSR1", "IGNORE")
            Signal.trap("SIGTERM", "IGNORE")
          end
        end

        # Sets a thread local variable as to whether we should or
        # should not record sql in the current thread. Returns the
        # previous value, if there is one
        def set_record_sql(should_record) # THREAD_LOCAL_ACCESS
          state = Tracer.state
          prev = state.record_sql
          state.record_sql = should_record
          prev.nil? || prev
        end

        # Push flag indicating whether we should be tracing in this
        # thread. This uses a stack which allows us to disable tracing
        # children of a transaction without affecting the tracing of
        # the whole transaction
        def push_trace_execution_flag(should_trace = false) # THREAD_LOCAL_ACCESS
          Tracer.state.push_traced(should_trace)
        end

        # Pop the current trace execution status.  Restore trace execution status
        # to what it was before we pushed the current flag.
        def pop_trace_execution_flag # THREAD_LOCAL_ACCESS
          Tracer.state.pop_traced
        end

        # Clear out the metric data, errors, and transaction traces, etc.
        def drop_buffered_data
          @stats_engine.reset!
          @error_collector.drop_buffered_data
          @transaction_sampler.reset!
          @transaction_event_recorder.drop_buffered_data
          @custom_event_aggregator.reset!
          @span_event_aggregator.reset!
          @log_event_aggregator.reset!
          @sql_sampler.reset!

          if Agent.config[:clear_transaction_state_after_fork]
            Tracer.clear_state
          end
        end

        # Clear out state for any objects that we know lock from our parents
        # This is necessary for cases where we're in a forked child and Ruby
        # might be holding locks for background thread that aren't there anymore.
        def reset_objects_with_locks
          @stats_engine = StatsEngine.new
        end

        def flush_pipe_data
          if connected? && @service.is_a?(PipeService)
            transmit_data
            transmit_analytic_event_data
            transmit_custom_event_data
            transmit_error_event_data
            transmit_span_event_data
            transmit_log_event_data
          end
        end

        private

        # A shorthand for NewRelic::Control.instance
        def control
          NewRelic::Control.instance
        end

        # This module is an artifact of a refactoring of the connect
        # method - all of its methods are used in that context, so it
        # can be refactored at will. It should be fully tested
        module Connect
          # number of attempts we've made to contact the server
          attr_accessor :connect_attempts

          # Disconnect just sets the connect state to disconnected, preventing
          # further retries.
          def disconnect
            @connect_state = :disconnected
            true
          end

          def connected?
            @connect_state == :connected
          end

          def disconnected?
            @connect_state == :disconnected
          end

          # Don't connect if we're already connected, or if we tried to connect
          # and were rejected with prejudice because of a license issue, unless
          # we're forced to by force_reconnect.
          def should_connect?(force = false)
            force || (!connected? && !disconnected?)
          end

          # Per the spec at
          # /agents/agent-specs/Collector-Response-Handling.md, retry
          # connections after a specific backoff sequence to prevent
          # hammering the server.
          def connect_retry_period
            NewRelic::CONNECT_RETRY_PERIODS[connect_attempts] || NewRelic::MAX_RETRY_PERIOD
          end

          def note_connect_failure
            self.connect_attempts += 1
          end

          # When we have a problem connecting to the server, we need
          # to tell the user what happened, since this is not an error
          # we can handle gracefully.
          def log_error(error)
            ::NewRelic::Agent.logger.error("Error establishing connection with New Relic Service at #{control.server}:", error)
          end

          # When the server sends us an error with the license key, we
          # want to tell the user that something went wrong, and let
          # them know where to go to get a valid license key
          #
          # After this runs, it disconnects the agent so that it will
          # no longer try to connect to the server, saving the
          # application and the server load
          def handle_license_error(error)
            ::NewRelic::Agent.logger.error( \
              error.message, \
              "Visit NewRelic.com to obtain a valid license key, or to upgrade your account."
            )
            disconnect
          end

          def handle_unrecoverable_agent_error(error)
            ::NewRelic::Agent.logger.error(error.message)
            disconnect
            shutdown
          end

          # Checks whether we should send environment info, and if so,
          # returns the snapshot from the local environment.
          # Generating the EnvironmentReport has the potential to trigger
          # require calls in Rails environments, so this method should only
          # be called synchronously from on the main thread.
          def environment_for_connect
            @environment_report ||= Agent.config[:send_environment_info] ? Array(EnvironmentReport.new) : []
          end

          # Constructs and memoizes an event_harvest_config hash to be used in
          # the payload sent during connect (and reconnect)
          def event_harvest_config
            @event_harvest_config ||= Configuration::EventHarvestConfig.from_config(Agent.config)
          end

          # Builds the payload to send to the connect service,
          # connects, then configures the agent using the response from
          # the connect service
          def connect_to_server
            request_builder = ::NewRelic::Agent::Connect::RequestBuilder.new( \
              @service,
              Agent.config,
              event_harvest_config,
              environment_for_connect
            )
            connect_response = @service.connect(request_builder.connect_payload)

            response_handler = ::NewRelic::Agent::Connect::ResponseHandler.new(self, Agent.config)
            response_handler.configure_agent(connect_response)

            log_connection(connect_response) if connect_response
            connect_response
          end

          # Logs when we connect to the server, for debugging purposes
          # - makes sure we know if an agent has not connected
          def log_connection(config_data)
            ::NewRelic::Agent.logger.debug("Connected to NewRelic Service at #{@service.collector.name}")
            ::NewRelic::Agent.logger.debug("Agent Run       = #{@service.agent_id}.")
            ::NewRelic::Agent.logger.debug("Connection data = #{config_data.inspect}")
            if config_data['messages'] && config_data['messages'].any?
              log_collector_messages(config_data['messages'])
            end
          end

          def log_collector_messages(messages)
            messages.each do |message|
              ::NewRelic::Agent.logger.send(message['level'].downcase, message['message'])
            end
          end

          # apdex_f is always 4 times the apdex_t
          def apdex_f
            (4 * Agent.config[:apdex_t]).to_f
          end

          class WaitOnConnectTimeout < StandardError
          end

          # Used for testing to let us know we've actually started to wait
          def waited_on_connect?
            @waited_on_connect
          end

          def signal_connected
            @wait_on_connect_mutex.synchronize do
              @wait_on_connect_condition.signal
            end
          end

          def wait_on_connect(timeout)
            return if connected?

            @waited_on_connect = true
            NewRelic::Agent.logger.debug("Waiting on connect to complete.")

            @wait_on_connect_mutex.synchronize do
              @wait_on_connect_condition.wait(@wait_on_connect_mutex, timeout)
            end

            unless connected?
              raise WaitOnConnectTimeout, "Agent was unable to connect in #{timeout} seconds."
            end
          end
        end
        include Connect

        def container_for_endpoint(endpoint)
          case endpoint
          when :metric_data then @stats_engine
          when :transaction_sample_data then @transaction_sampler
          when :error_data then @error_collector.error_trace_aggregator
          when :error_event_data then @error_collector.error_event_aggregator
          when :analytic_event_data then transaction_event_aggregator
          when :custom_event_data then @custom_event_aggregator
          when :span_event_data then span_event_aggregator
          when :sql_trace_data then @sql_sampler
          when :log_event_data then @log_event_aggregator
          end
        end

        def merge_data_for_endpoint(endpoint, data)
          if data && !data.empty?
            container = container_for_endpoint(endpoint)
            if container.respond_to?(:has_metadata?) && container.has_metadata?
              container_for_endpoint(endpoint).merge!(data, false)
            else
              container_for_endpoint(endpoint).merge!(data)
            end
          end
        rescue => e
          NewRelic::Agent.logger.error("Error while merging #{endpoint} data from child: ", e)
        end

        public :merge_data_for_endpoint

        # Establish a connection to New Relic servers.
        #
        # By default, if a connection has already been established, this method
        # will be a no-op.
        #
        # @param [Hash] options
        # @option options [Boolean] :keep_retrying (true)
        #   If true, this method will block until a connection is successfully
        #   established, continuing to retry upon failure. If false, this method
        #   will return after either successfully connecting, or after failing
        #   once.
        #
        # @option options [Boolean] :force_reconnect (false)
        #   If true, this method will force establishment of a new connection
        #   with New Relic, even if there is already an existing connection.
        #   This is useful primarily when re-establishing a new connection after
        #   forking off from a parent process.
        #
        def connect(options = {})
          defaults = {
            :keep_retrying => Agent.config[:keep_retrying],
            :force_reconnect => Agent.config[:force_reconnect]
          }
          opts = defaults.merge(options)

          return unless should_connect?(opts[:force_reconnect])

          ::NewRelic::Agent.logger.debug("Connecting Process to New Relic: #$0")
          connect_to_server
          @connected_pid = $$
          @connect_state = :connected
          signal_connected
        rescue NewRelic::Agent::ForceDisconnectException => e
          handle_force_disconnect(e)
        rescue NewRelic::Agent::LicenseException => e
          handle_license_error(e)
        rescue NewRelic::Agent::UnrecoverableAgentException => e
          handle_unrecoverable_agent_error(e)
        rescue StandardError, Timeout::Error, NewRelic::Agent::ServerConnectionException => e
          # Allow a killed (aborting) thread to continue exiting during shutdown.
          # See: https://github.com/newrelic/newrelic-ruby-agent/issues/340
          raise if Thread.current.status == 'aborting'

          log_error(e)
          if opts[:keep_retrying]
            note_connect_failure
            ::NewRelic::Agent.logger.info("Will re-attempt in #{connect_retry_period} seconds")
            sleep(connect_retry_period)
            retry
          end
        rescue Exception => e
          ::NewRelic::Agent.logger.error("Exception of unexpected type during Agent#connect():", e)

          raise
        end

        # Delegates to the control class to determine the root
        # directory of this project
        def determine_home_directory
          control.root
        end

        # Harvests data from the given container, sends it to the named endpoint
        # on the service, and automatically merges back in upon a recoverable
        # failure.
        #
        # The given container should respond to:
        #
        #  #harvest!
        #    returns a payload that contains enumerable collection of data items and
        #    optional metadata to be sent to the collector.
        #
        #  #reset!
        #    drop any stored data and reset to a clean state.
        #
        #  #merge!(payload)
        #    merge the given payload back into the internal buffer of the
        #    container, so that it may be harvested again later.
        #
        def harvest_and_send_from_container(container, endpoint)
          payload = harvest_from_container(container, endpoint)
          sample_count = harvest_size(container, payload)
          if sample_count > 0
            NewRelic::Agent.logger.debug("Sending #{sample_count} items to #{endpoint}")
            send_data_to_endpoint(endpoint, payload, container)
          end
        end

        def harvest_size(container, items)
          if container.respond_to?(:has_metadata?) && container.has_metadata? && !items.empty?
            items.last.size
          else
            items.size
          end
        end

        def harvest_from_container(container, endpoint)
          items = []
          begin
            items = container.harvest!
          rescue => e
            NewRelic::Agent.logger.error("Failed to harvest #{endpoint} data, resetting. Error: ", e)
            container.reset!
          end
          items
        end

        def send_data_to_endpoint(endpoint, payload, container)
          begin
            @service.send(endpoint, payload)
          rescue ForceRestartException, ForceDisconnectException
            raise
          rescue SerializationError => e
            NewRelic::Agent.logger.warn("Failed to serialize data for #{endpoint}, discarding. Error: ", e)
          rescue UnrecoverableServerException => e
            NewRelic::Agent.logger.warn("#{endpoint} data was rejected by remote service, discarding. Error: ", e)
          rescue ServerConnectionException => e
            log_remote_unavailable(endpoint, e)
            container.merge!(payload)
          rescue => e
            NewRelic::Agent.logger.info("Unable to send #{endpoint} data, will try again later. Error: ", e)
            container.merge!(payload)
          end
        end

        def harvest_and_send_timeslice_data
          TransactionTimeAggregator.harvest!
          harvest_and_send_from_container(@stats_engine, :metric_data)
        end

        def harvest_and_send_slowest_sql
          harvest_and_send_from_container(@sql_sampler, :sql_trace_data)
        end

        # This handles getting the transaction traces and then sending
        # them across the wire.  This includes gathering SQL
        # explanations, stripping out stack traces, and normalizing
        # SQL.  note that we explain only the sql statements whose
        # nodes' execution times exceed our threshold (to avoid
        # unnecessary overhead of running explains on fast queries.)
        def harvest_and_send_transaction_traces
          harvest_and_send_from_container(@transaction_sampler, :transaction_sample_data)
        end

        def harvest_and_send_for_agent_commands
          harvest_and_send_from_container(@agent_command_router, :profile_data)
        end

        def harvest_and_send_errors
          harvest_and_send_from_container(@error_collector.error_trace_aggregator, :error_data)
        end

        def harvest_and_send_analytic_event_data
          harvest_and_send_from_container(transaction_event_aggregator, :analytic_event_data)
          harvest_and_send_from_container(synthetics_event_aggregator, :analytic_event_data)
        end

        def harvest_and_send_custom_event_data
          harvest_and_send_from_container(@custom_event_aggregator, :custom_event_data)
        end

        def harvest_and_send_error_event_data
          harvest_and_send_from_container(@error_collector.error_event_aggregator, :error_event_data)
        end

        def harvest_and_send_span_event_data
          harvest_and_send_from_container(span_event_aggregator, :span_event_data)
        end

        def harvest_and_send_log_event_data
          harvest_and_send_from_container(@log_event_aggregator, :log_event_data)
        end

        def check_for_and_handle_agent_commands
          begin
            @agent_command_router.check_for_and_handle_agent_commands
          rescue ForceRestartException, ForceDisconnectException
            raise
          rescue UnrecoverableServerException => e
            NewRelic::Agent.logger.warn("get_agent_commands message was rejected by remote service, discarding. Error: ", e)
          rescue ServerConnectionException => e
            log_remote_unavailable(:get_agent_commands, e)
          rescue => e
            NewRelic::Agent.logger.info("Error during check_for_and_handle_agent_commands, will retry later: ", e)
          end
        end

        def log_remote_unavailable(endpoint, e)
          NewRelic::Agent.logger.debug("Unable to send #{endpoint} data, will try again later. Error: ", e)
          NewRelic::Agent.record_metric("Supportability/remote_unavailable", 0.0)
          NewRelic::Agent.record_metric("Supportability/remote_unavailable/#{endpoint.to_s}", 0.0)
        end

        TRANSACTION_EVENT = "TransactionEvent".freeze
        def transmit_analytic_event_data
          transmit_single_data_type(:harvest_and_send_analytic_event_data, TRANSACTION_EVENT)
        end

        CUSTOM_EVENT = "CustomEvent".freeze
        def transmit_custom_event_data
          transmit_single_data_type(:harvest_and_send_custom_event_data, CUSTOM_EVENT)
        end

        ERROR_EVENT = "ErrorEvent".freeze
        def transmit_error_event_data
          transmit_single_data_type(:harvest_and_send_error_event_data, ERROR_EVENT)
        end

        SPAN_EVENT = "SpanEvent".freeze
        def transmit_span_event_data
          transmit_single_data_type(:harvest_and_send_span_event_data, SPAN_EVENT)
        end

        LOG_EVENT = "LogEvent".freeze
        def transmit_log_event_data
          transmit_single_data_type(:harvest_and_send_log_event_data, LOG_EVENT)
        end

        def transmit_single_data_type(harvest_method, supportability_name)
          now = Process.clock_gettime(Process::CLOCK_MONOTONIC)

          msg = "Sending #{supportability_name} data to New Relic Service"
          ::NewRelic::Agent.logger.debug(msg)

          @service.session do # use http keep-alive
            self.send(harvest_method)
          end
        ensure
          duration = Process.clock_gettime(Process::CLOCK_MONOTONIC) - now
          NewRelic::Agent.record_metric("Supportability/#{supportability_name}Harvest", duration)
        end

        def transmit_data
          now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
          ::NewRelic::Agent.logger.debug("Sending data to New Relic Service")

          @events.notify(:before_harvest)
          @service.session do # use http keep-alive
            harvest_and_send_errors
            harvest_and_send_error_event_data
            harvest_and_send_transaction_traces
            harvest_and_send_slowest_sql
            harvest_and_send_timeslice_data
            harvest_and_send_span_event_data
            harvest_and_send_log_event_data

            check_for_and_handle_agent_commands
            harvest_and_send_for_agent_commands
          end
        ensure
          NewRelic::Agent::Database.close_connections
          duration = Process.clock_gettime(Process::CLOCK_MONOTONIC) - now
          NewRelic::Agent.record_metric('Supportability/Harvest', duration)
        end

        # This method contacts the server to send remaining data and
        # let the server know that the agent is shutting down - this
        # allows us to do things like accurately set the end of the
        # lifetime of the process
        #
        # If this process comes from a parent process, it will not
        # disconnect, so that the parent process can continue to send data
        def graceful_disconnect
          if connected?
            begin
              @service.request_timeout = 10

              @events.notify(:before_shutdown)
              transmit_data
              transmit_analytic_event_data
              transmit_custom_event_data
              transmit_error_event_data
              transmit_span_event_data
              transmit_log_event_data

              if @connected_pid == $$ && !@service.kind_of?(NewRelic::Agent::NewRelicService)
                ::NewRelic::Agent.logger.debug("Sending New Relic service agent run shutdown message")
                @service.shutdown
              else
                ::NewRelic::Agent.logger.debug("This agent connected from parent process #{@connected_pid}--not sending shutdown")
              end
              ::NewRelic::Agent.logger.debug("Graceful disconnect complete")
            rescue Timeout::Error, StandardError => e
              ::NewRelic::Agent.logger.debug("Error when disconnecting #{e.class.name}: #{e.message}")
            end
          else
            ::NewRelic::Agent.logger.debug("Bypassing graceful disconnect - agent not connected")
          end
        end
      end

      extend ClassMethods
      include InstanceMethods
    end
  end
end