Method: ScoutApm::Instruments::Process::ProcessCpu#run

Defined in:
lib/scout_apm/instruments/process/process_cpu.rb

#run ⇒ Object

TODO: Figure out a good default instead of nil



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# File 'lib/scout_apm/instruments/process/process_cpu.rb', line 46

def run
  res = nil

  t = ::Process.times
  now = Time.now
  utime = t.utime
  stime = t.stime

  wall_clock_elapsed  = now - last_run
  if wall_clock_elapsed < 0
    save_times(now, utime, stime)
    logger.info "#{human_name}: Negative time elapsed.  now: #{now}, last_run: #{last_run}, total time: #{wall_clock_elapsed}."
    return nil
  end

  utime_elapsed   = utime - last_utime
  stime_elapsed   = stime - last_stime
  process_elapsed = utime_elapsed + stime_elapsed

  # This can happen right after a fork.  This class starts up in
  # pre-fork, records {u,s}time, then forks. This resets {u,s}time to 0
  if process_elapsed < 0
    save_times(now, utime, stime)
    logger.debug "#{human_name}: Negative process time elapsed.  utime: #{utime_elapsed}, stime: #{stime_elapsed}, total time: #{process_elapsed}. This is normal to see when starting a forking web server."
    return nil
  end

  # Normalized to # of processors
  normalized_wall_clock_elapsed = wall_clock_elapsed * num_processors

  # If somehow we run for 0 seconds between calls, don't try to divide by 0
  res = if normalized_wall_clock_elapsed == 0
          0
        else
          ( process_elapsed / normalized_wall_clock_elapsed )*100
        end

  if res < 0
    save_times(now, utime, stime)
    logger.info "#{human_name}: Negative CPU.  #{process_elapsed} / #{normalized_wall_clock_elapsed} * 100 ==> #{res}"
    return nil
  end

  save_times(now, utime, stime)

  logger.debug "#{human_name}: #{res.inspect} [#{num_processors} CPU(s)]"

  return res
end