84291b6014
I hope that the windows test suite failure on appveyor was fixed by updating to a newer windows there. I have not been able to reproduce that failure in a windows 11 VM run locally.
84 lines
2.9 KiB
Haskell
84 lines
2.9 KiB
Haskell
{- git-annex vector clocks
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-
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- These are basically a timestamp. However, when logging a new
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- value, if the old value has a vector clock that is the same or greater
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- than the current vector clock, the old vector clock is incremented.
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- This way, clock skew does not cause confusion.
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-
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- Copyright 2017-2021 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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module Annex.VectorClock (
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module Annex.VectorClock,
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module Types.VectorClock,
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) where
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import Types.VectorClock
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import Annex.Common
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import qualified Annex
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import Utility.TimeStamp
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import Data.ByteString.Builder
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import qualified Data.ByteString as B
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import qualified Data.Attoparsec.ByteString.Lazy as A
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currentVectorClock :: Annex CandidateVectorClock
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currentVectorClock = liftIO =<< Annex.getState Annex.getvectorclock
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-- Runs the action and uses the same vector clock throughout,
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-- except when it's necessary to use a newer one due to a past value having
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-- a newer vector clock.
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--
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-- When the action modifies several files in the git-annex branch,
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-- this can cause less space to be used, since the same vector clock
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-- value is used, which can compress better.
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--
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-- However, this should not be used when running a long-duration action,
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-- because the vector clock is based on the start of the action, and not on
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-- the later points where it writes changes. For example, if this were
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-- used across downloads of several files, the location log information
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-- would have an earlier vector clock than necessary, which might cause it
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-- to be disregarded in favor of other information that was collected
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-- at an earlier point in time than when the transfers completted and the
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-- log was written.
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reuseVectorClockWhile :: Annex a -> Annex a
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reuseVectorClockWhile = bracket setup cleanup . const
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where
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setup = do
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origget <- Annex.getState Annex.getvectorclock
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vc <- liftIO origget
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use (pure vc)
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return origget
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cleanup origget = use origget
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use vc = Annex.changeState $ \s ->
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s { Annex.getvectorclock = vc }
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-- Convert a candidate vector clock in to the final one to use,
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-- advancing it if necessary when necessary to get ahead of a previously
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-- used vector clock.
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advanceVectorClock :: CandidateVectorClock -> [VectorClock] -> VectorClock
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advanceVectorClock (CandidateVectorClock c) [] = VectorClock c
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advanceVectorClock (CandidateVectorClock c) prevs
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| prev >= VectorClock c = case prev of
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VectorClock v -> VectorClock (v + 1)
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Unknown -> VectorClock c
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| otherwise = VectorClock c
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where
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prev = maximum prevs
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formatVectorClock :: VectorClock -> String
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formatVectorClock Unknown = "0"
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formatVectorClock (VectorClock t) = show t
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buildVectorClock :: VectorClock -> Builder
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buildVectorClock = string7 . formatVectorClock
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parseVectorClock :: B.ByteString -> Maybe VectorClock
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parseVectorClock t = VectorClock <$> parsePOSIXTime t
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vectorClockParser :: A.Parser VectorClock
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vectorClockParser = VectorClock <$> parserPOSIXTime
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