src/Ganeti/DataCollectors/KvmRSS.hs

{-| kvm resident set size collector

It collects the resident set size (RSS) for all kvm
processes managed by Ganeti, i.e., the number of pages
the process has in RAM. The value is obtained
by taking the corresponding value from /proc/$pid/memstat.

-}

{-

Copyright (C) 2015 Google Inc.
All rights reserved.

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-}

module Ganeti.DataCollectors.KvmRSS
  ( dcName
  , dcVersion
  , dcFormatVersion
  , dcCategory
  , dcKind
  , dcReport
  ) where

import Control.Monad (liftM)
import Data.Char (isSpace)
import Data.Maybe (mapMaybe)
import Network.BSD (getHostName)
import System.FilePath ((</>))
import qualified Text.JSON as J
import Text.Printf (printf)

import Ganeti.BasicTypes
import Ganeti.Confd.ClientFunctions (getInstances)
import qualified Ganeti.Constants as C
import Ganeti.DataCollectors.Types
import Ganeti.Objects
import Ganeti.Path (kvmPidDir)

-- | The name of this data collector for the resident set size (RSS).
dcName :: String
dcName = C.dataCollectorKvmRSS

-- | The version number for the data format of this data collector.
dcFormatVersion :: Int
dcFormatVersion = 1

-- | The version of this data collector.
dcVersion :: DCVersion
dcVersion = DCVerBuiltin

-- | The category of this data collector.
dcCategory :: Maybe DCCategory
dcCategory = Nothing

-- | The kind of this data collector.
dcKind :: DCKind
dcKind = DCKPerf

-- | Parse the contents of a pid file.
parsePid :: Monad m => String -> m Int
parsePid s = case reads s of
  [(pid, r)] | all isSpace r -> return pid
  _ -> fail $ "Couldn't parse pid " ++ s

-- | From the contents of a memstat file get the resident set size,
-- in pages.
parseRss :: Monad m => String -> m Int
parseRss s =
  let drop1 = dropWhile isSpace . dropWhile (not . isSpace) . dropWhile isSpace
  in case reads (drop1 s) of
    [(n, _)] -> return n
    _ -> fail $ "Failed to parse memstat " ++ s

-- | For an instance, collect the resident set size, if available.
collectInstanceRSS :: String -> IO (Result (String, J.JSValue))
collectInstanceRSS inst = runResultT $ do
  piddir <- liftIO kvmPidDir
  let pidfile = piddir </> inst
  pidstring <- liftIO $ readFile pidfile
  pid <- parsePid pidstring
  let procfspath = printf "/proc/%d/statm" pid
  memstat <- liftIO $ readFile procfspath
  rss <- parseRss memstat
  return (inst, J.showJSON rss)

-- | The data exported by the data collector.
dcReport :: IO DCReport
dcReport = do
  node <- getHostName
  instances <- liftM (genericResult (const []) (mapMaybe instName . fst))
               . runResultT $ getInstances node Nothing Nothing
  reports <- liftM justOk $ mapM collectInstanceRSS instances
  buildReport dcName dcVersion dcFormatVersion dcCategory dcKind
           . J.JSObject $ J.toJSObject reports