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|
{- git-annex assistant daemon status
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-}
module Assistant.DaemonStatus where
import Common.Annex
import Utility.TempFile
import Assistant.ThreadedMonad
import Control.Concurrent
import System.Posix.Types
import Data.Time.Clock.POSIX
import Data.Time
import System.Locale
data DaemonStatus = DaemonStatus
-- False when the daemon is performing its startup scan
{ scanComplete :: Bool
-- Time when a previous process of the daemon was running ok
, lastRunning :: Maybe POSIXTime
}
deriving (Show)
type DaemonStatusHandle = MVar DaemonStatus
newDaemonStatus :: DaemonStatus
newDaemonStatus = DaemonStatus
{ scanComplete = False
, lastRunning = Nothing
}
getDaemonStatus :: DaemonStatusHandle -> Annex DaemonStatus
getDaemonStatus = liftIO . readMVar
modifyDaemonStatus :: DaemonStatusHandle -> (DaemonStatus -> DaemonStatus) -> Annex ()
modifyDaemonStatus handle a = liftIO $ modifyMVar_ handle (return . a)
{- Load any previous daemon status file, and store it in the MVar for this
- process to use as its DaemonStatus. -}
startDaemonStatus :: Annex DaemonStatusHandle
startDaemonStatus = do
file <- fromRepo gitAnnexDaemonStatusFile
status <- liftIO $
catchDefaultIO (readDaemonStatusFile file) newDaemonStatus
liftIO $ newMVar status { scanComplete = False }
{- This thread wakes up periodically and writes the daemon status to disk. -}
daemonStatusThread :: ThreadState -> DaemonStatusHandle -> IO ()
daemonStatusThread st handle = do
checkpoint
forever $ do
threadDelay tenMinutes
checkpoint
where
checkpoint = runThreadState st $ do
file <- fromRepo gitAnnexDaemonStatusFile
status <- getDaemonStatus handle
liftIO $ writeDaemonStatusFile file status
tenMinutes = 10 * 60 * 1000000 -- microseconds
{- Don't just dump out the structure, because it will change over time,
- and parts of it are not relevant. -}
writeDaemonStatusFile :: FilePath -> DaemonStatus -> IO ()
writeDaemonStatusFile file status =
viaTmp writeFile file =<< serialized <$> getPOSIXTime
where
serialized now = unlines
[ "lastRunning:" ++ show now
, "scanComplete:" ++ show (scanComplete status)
]
readDaemonStatusFile :: FilePath -> IO DaemonStatus
readDaemonStatusFile file = parse <$> readFile file
where
parse = foldr parseline newDaemonStatus . lines
parseline line status
| key == "lastRunning" = parseval readtime $ \v ->
status { lastRunning = Just v }
| key == "scanComplete" = parseval readish $ \v ->
status { scanComplete = v }
| otherwise = status -- unparsable line
where
(key, value) = separate (== ':') line
parseval parser a = maybe status a (parser value)
readtime s = do
d <- parseTime defaultTimeLocale "%s%Qs" s
Just $ utcTimeToPOSIXSeconds d
{- Checks if a time stamp was made after the daemon was lastRunning.
-
- Some slop is built in; this really checks if the time stamp was made
- at least ten minutes after the daemon was lastRunning. This is to
- ensure the daemon shut down cleanly, and deal with minor clock skew.
-
- If the daemon has never ran before, this always returns False.
-}
afterLastDaemonRun :: EpochTime -> DaemonStatus -> Bool
afterLastDaemonRun timestamp status = maybe False (< t) (lastRunning status)
where
t = realToFrac (timestamp + slop) :: POSIXTime
slop = 10 * 60
|
