67c8ef7de2
SampleMVar won't work; between getting the current value and changing it, another thread could made a change, which would get lost. TMVar works well; this update situation is handled by atomic transactions.
46 lines
1.4 KiB
Haskell
46 lines
1.4 KiB
Haskell
{- git-annex assistant push tracking
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-
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- Copyright 2012 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Assistant.Pushes where
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import Common.Annex
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import Control.Concurrent.STM
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import Data.Time.Clock
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import qualified Data.Map as M
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{- Track the most recent push failure for each remote. -}
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type PushMap = M.Map Remote UTCTime
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type FailedPushMap = TMVar PushMap
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{- The TMVar starts empty, and is left empty when there are no
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- failed pushes. This way we can block until there are some failed pushes.
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-}
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newFailedPushMap :: IO FailedPushMap
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newFailedPushMap = atomically newEmptyTMVar
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{- Blocks until there are failed pushes.
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- Returns Remotes whose pushes failed a given time duration or more ago.
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- (This may be an empty list.) -}
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getFailedPushesBefore :: FailedPushMap -> NominalDiffTime -> IO [Remote]
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getFailedPushesBefore v duration = do
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m <- atomically $ readTMVar v
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now <- getCurrentTime
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return $ M.keys $ M.filter (not . toorecent now) m
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where
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toorecent now time = now `diffUTCTime` time < duration
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{- Modifies the map. -}
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changeFailedPushMap :: FailedPushMap -> (PushMap -> PushMap) -> IO ()
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changeFailedPushMap v a = atomically $
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store . a . fromMaybe M.empty =<< tryTakeTMVar v
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where
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{- tryTakeTMVar empties the TMVar; refill it only if
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- the modified map is not itself empty -}
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store m
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| m == M.empty = noop
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| otherwise = putTMVar v $! m
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