db89e39df6
It's possible for two processes or threads to both be doing the same operation at the same time. Eg, both dropping the same key. If one finishes and updates the rollingtotal, then the other one needs to be prevented from later updating the rollingtotal as well. And they could finish at the same time, or with some time in between. Addressed this by making updateRepoSize be called with the journal locked, and only once it's been determined that there is an actual location change to record in the log. updateRepoSize waits for the database to be updated. When there is a redundant operation, updateRepoSize won't be called, and the redundant LiveUpdate will be removed from the database on garbage collection. But: There will be a window where the redundant LiveUpdate is still visible in the db, and processes can see it, combine it with the rollingtotal, and arrive at the wrong size. This is a small window, but it still ought to be addressed. Unsure if it would always be safe to remove the redundant LiveUpdate? Consider the case where two drops and a get are all running concurrently somehow, and the order they finish is [drop, get, drop]. The second drop seems redundant to the first, but it would not be safe to remove it. While this seems unlikely, it's hard to rule out that a get and drop at different stages can both be running at the same time.
55 lines
1.6 KiB
Haskell
55 lines
1.6 KiB
Haskell
{- Remote content identifier logs.
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-
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- Copyright 2019 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 Logs.ContentIdentifier (
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module X,
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recordContentIdentifier,
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getContentIdentifiers,
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) where
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import Annex.Common
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import Logs
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import Logs.MapLog
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import Types.Import
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import Types.RemoteState
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import qualified Annex.Branch
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import Logs.ContentIdentifier.Pure as X
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import qualified Annex
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import qualified Data.Map as M
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import Data.List.NonEmpty (NonEmpty(..))
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import qualified Data.List.NonEmpty as NonEmpty
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-- | Records a remote's content identifier and the key that it corresponds to.
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--
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-- A remote may use multiple content identifiers for the same key over time,
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-- so ones that were recorded before are preserved.
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recordContentIdentifier :: RemoteStateHandle -> ContentIdentifier -> Key -> Annex ()
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recordContentIdentifier (RemoteStateHandle u) cid k = do
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c <- currentVectorClock
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config <- Annex.getGitConfig
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void $ Annex.Branch.maybeChange
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(Annex.Branch.RegardingUUID [u])
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(remoteContentIdentifierLogFile config k)
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(addcid c . parseLog)
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noop
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where
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addcid c v
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| cid `elem` l = Nothing -- no change needed
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| otherwise = Just $ buildLog $
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changeMapLog c u (cid :| l) v
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where
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m = simpleMap v
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l = contentIdentifierList (M.lookup u m)
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-- | Get all known content identifiers for a key.
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getContentIdentifiers :: Key -> Annex [(RemoteStateHandle, [ContentIdentifier])]
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getContentIdentifiers k = do
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config <- Annex.getGitConfig
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map (\(u, l) -> (RemoteStateHandle u, NonEmpty.toList l) )
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. M.toList . simpleMap . parseLog
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<$> Annex.Branch.get (remoteContentIdentifierLogFile config k)
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