# -*- ruby -*-

# vim: set noet nosta sw=4 ts=4 :

require 'arborist/monitor/snmp' unless defined?( Arborist::Monitor::SNMP )

# Machine load/cpu checks.

#

# Sets current 1, 5, and 15 minute loads under the 'load' attribute,

# and calculates/warns on cpu overutilization.

#

class Arborist::Monitor::SNMP::CPU

	include Arborist::Monitor::SNMP

	extend Configurability, Loggability

	log_to :arborist_snmp

	# OIDS for discovering system load.

	#

	OIDS = {

		load: '1.3.6.1.4.1.2021.10.1.3',

		cpu:  '1.3.6.1.2.1.25.3.3.1.2'

	}

	# When walking load OIDS, the iterator count matches

	# these labels.

	#

	LOADKEYS = %i[ load1 load5 load15 ]

	# Global defaults for instances of this monitor

	#

	configurability( 'arborist.snmp.cpu' ) do

		# What overutilization percentage qualifies as a warning

		setting :warn_at, default: 80

	end

	### Return the properties used by this monitor.

	###

	def self::node_properties

		return USED_PROPERTIES

	end

	### Class #run creates a new instance and immediately runs it.

	###

	def self::run( nodes )

		return new.run( nodes )

	end

	### Perform the monitoring checks.

	###

	def run( nodes )

		super do |host, snmp|

			self.find_load( host, snmp )

		end

	end

	#########

	protected

	#########

	### Find load data, add additional niceties for reporting.

	###

	def format_load( snmp )

		info = { cpu: {}, load: {} }

		cpus = snmp.walk( oid: OIDS[:cpu] ).each_with_object( [] ) do |(_, value), acc|

			acc << value

		end

		info[ :cpu ][ :count ] = cpus.size

		# Windows SNMP doesn't have a concept of "load" over time,

		# so we have to just use the current averaged CPU usage.

		#

		# This means that windows machines will very likely want to

		# adjust the default "overutilization" number, considering

		# it's really just how much of the CPU is used at the time of

		# the monitor run, along with liberal use of the Observer "only

		# alert after X events" pragmas.

		#

		if self.system =~ /windows\s+/i

			info[ :cpu ][ :usage ] = cpus.inject( :+ ).to_f / cpus.size

			info[ :message ] = "System is %0.1f%% in use." % [ info[ :cpu ][ :usage ] ]

		# UCDavis stuff is better for alerting only after there has been

		# an extended load event.  Use the 5 minute average to avoid

		# state changes on transient spikes.

		#

		else

			snmp.walk( oid: OIDS[:load] ).each_with_index do |(_, value), idx|

				next unless LOADKEYS[ idx ]

				info[ :load ][ LOADKEYS[idx] ] = value.to_f

			end

			percentage = (( ( info[:load][ :load5 ] / cpus.size) - 1 ) * 100 ).round( 1 )

			if percentage < 0

				info[ :message ] = "System is %0.1f%% idle." % [ percentage.abs ]

				info[ :cpu ][ :usage ] = percentage + 100

			else

				info[ :message ] = "System is %0.1f%% overloaded." % [ percentage ]

				info[ :cpu ][ :usage ] = percentage

			end

		end

		return info

	end

	### Collect the load information for +host+ from an existing

	### (and open) +snmp+ connection.

	###

	def find_load( host, snmp )

		info = self.format_load( snmp )

		warn_at = config[ 'warn_at' ] || self.class.warn_at

		usage   = info.dig( :cpu, :usage ) || 0

		if usage >= warn_at

			info[ :warning ] = "%0.1f utilization exceeds %0.1f percent" % [ usage, warn_at ]

		end

		self.results[ host ] = info

	end

end # class Arborist::Monitor::SNMP::CPU