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{-| @/proc/stat@ data collector.

-}

{-

Copyright (C) 2013 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.DataCollectors.CPUload

  ( dcName

  , dcVersion

  , dcFormatVersion

  , dcCategory

  , dcKind

  , dcReport

  , dcUpdate

  ) where

import qualified Control.Exception as E

import Data.Attoparsec.Text.Lazy as A

import Data.Text.Lazy (pack, unpack)

import qualified Text.JSON as J

import qualified Data.Sequence as Seq

import System.Posix.Unistd (getSysVar, SysVar(ClockTick))

import qualified Ganeti.BasicTypes as BT

import qualified Ganeti.Constants as C

import Ganeti.Cpu.LoadParser(cpustatParser)

import Ganeti.DataCollectors.Types

import Ganeti.Utils

import Ganeti.Cpu.Types

-- | The default path of the CPU status file.

-- It is hardcoded because it is not likely to change.

defaultFile :: FilePath

defaultFile = C.statFile

-- | The buffer size of the values kept in the map.

bufferSize :: Int

bufferSize = C.cpuavgloadBufferSize

-- | The window size of the values that will export the average load.

windowSize :: Integer

windowSize = toInteger C.cpuavgloadWindowSize

-- | The default setting for the maximum amount of not parsed character to

-- print in case of error.

-- It is set to use most of the screen estate on a standard 80x25 terminal.

-- TODO: add the possibility to set this with a command line parameter.

defaultCharNum :: Int

defaultCharNum = 80*20

-- | The name of this data collector.

dcName :: String

dcName = "cpu-avg-load"

-- | The version of this data collector.

dcVersion :: DCVersion

dcVersion = DCVerBuiltin

-- | The version number for the data format of this data collector.

dcFormatVersion :: Int

dcFormatVersion = 1

-- | The category of this data collector.

dcCategory :: Maybe DCCategory

dcCategory = Nothing

-- | The kind of this data collector.

dcKind :: DCKind

dcKind = DCKPerf

-- | The data exported by the data collector, taken from the default location.

dcReport :: Maybe CollectorData -> IO DCReport

dcReport colData =

  let cpuLoadData =

        case colData of

          Nothing -> Seq.empty

          Just colData' ->

            case colData' of

              CPULoadData v -> v

  in buildDCReport cpuLoadData

-- | Data stored by the collector in mond's memory.

type Buffer = Seq.Seq (Integer, [Int])

-- | Compute the load from a CPU.

computeLoad :: CPUstat -> Int

computeLoad cpuData =

  csUser cpuData + csNice cpuData + csSystem cpuData

  + csIowait cpuData + csIrq cpuData + csSoftirq cpuData

  + csSteal cpuData + csGuest cpuData + csGuestNice cpuData

-- | Reads and Computes the load for each CPU.

dcCollectFromFile :: FilePath -> IO (Integer, [Int])

dcCollectFromFile inputFile = do

  contents <-

    ((E.try $ readFile inputFile) :: IO (Either IOError String)) >>=

      exitIfBad "reading from file" . either (BT.Bad . show) BT.Ok

  cpustatData <-

    case A.parse cpustatParser $ pack contents of

      A.Fail unparsedText contexts errorMessage -> exitErr $

        show (Prelude.take defaultCharNum $ unpack unparsedText) ++ "\n"

          ++ show contexts ++ "\n" ++ errorMessage

      A.Done _ cpustatD -> return cpustatD

  now <- getCurrentTime

  let timestamp = now :: Integer

  return (timestamp, map computeLoad cpustatData)

-- | Returns the collected data in the appropriate type.

dcCollect :: IO Buffer

dcCollect  = do

  l <- dcCollectFromFile defaultFile

  return (Seq.singleton l)

-- | Formats data for JSON transformation.

formatData :: [Double] -> CPUavgload

formatData [] = CPUavgload (0 :: Int) [] (0 :: Double)

formatData l@(x:xs) = CPUavgload (length l - 1) xs x

-- | Update a Map Entry.

updateEntry :: Buffer -> Buffer -> Buffer

updateEntry newBuffer mapEntry =

  (Seq.><) newBuffer

  (if Seq.length mapEntry < bufferSize

    then mapEntry

    else Seq.drop 1 mapEntry)

-- | Updates the given Collector data.

dcUpdate :: Maybe CollectorData -> IO CollectorData

dcUpdate mcd = do

  v <- dcCollect

  let new_v =

        case mcd of

          Nothing -> v

          Just cd ->

            case cd of

              CPULoadData old_v -> updateEntry v old_v

  new_v `seq` return $ CPULoadData new_v

-- | Computes the average load for every CPU and the overall from data read

-- from the map.

computeAverage :: Buffer -> Integer -> Integer -> [Double]

computeAverage s w ticks =

  let window = Seq.takeWhileL ((> w) . fst) s

      go Seq.EmptyL          _                    = []

      go _                   Seq.EmptyR           = []

      go (leftmost Seq.:< _) (_ Seq.:> rightmost) = do

        let (timestampL, listL) = leftmost

            (timestampR, listR) = rightmost

            work = zipWith (-) listL listR

            overall = (timestampL - timestampR) * ticks

        map (\x -> fromIntegral x / fromIntegral overall) work

  in go (Seq.viewl window) (Seq.viewr window)

-- | This function computes the JSON representation of the CPU load.

buildJsonReport :: Buffer -> IO J.JSValue

buildJsonReport v = do

  ticks <- getSysVar ClockTick

  let res = computeAverage v windowSize ticks

  return . J.showJSON $ formatData res

-- | This function computes the DCReport for the CPU load.

buildDCReport :: Buffer -> IO DCReport

buildDCReport v  =

  buildJsonReport v >>=

    buildReport dcName dcVersion dcFormatVersion dcCategory dcKind