d06aee7ce0
Fixed inversion of control issue, so the tree is recorded in streamLogFile finalizer. Sponsored-by: Leon Schuermann on Patreon
101 lines
3.2 KiB
Haskell
101 lines
3.2 KiB
Haskell
{- git-annex migration logs
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-
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- To record a migration in the git-annex branch as space efficiently as
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- possible, it is stored as a tree which contains two subtrees 'old' and 'new'.
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- The subtrees each contain the same filenames, which point to the old
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- and new keys respectively.
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-
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- When the user commits the migrated files to their HEAD branch, that will
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- store pointers to the new keys in git. And pointers to the old keys
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- already exist in git. So recording the migration this way avoids
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- injecting any new objects into git, besides the two trees. Note that for
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- this to be the case, care has to be taken to record the migration
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- using the same symlink targets or pointer file contents as are used in
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- the HEAD branch.
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-
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- The filenames used in the trees are not the original filenames, to avoid
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- running migrate in a throwaway branch unexpectedly recording that
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- branch's contents.
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-
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- Copyright 2023 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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{-# LANGUAGE OverloadedStrings, BangPatterns #-}
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module Logs.Migrate (
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MigrationRecord(..),
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logMigration,
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commitMigration,
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) where
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import Annex.Common
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import qualified Git
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import qualified Annex
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import qualified Annex.Branch
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import Git.Types
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import Git.Tree
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import Git.FilePath
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import Logs.File
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import Logs
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import qualified Data.ByteString.Lazy as L
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import Control.Concurrent.STM
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-- | What to use to record a migration. This should be the same Sha that is
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-- used to as the content of the annexed file in the HEAD branch.
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newtype MigrationRecord = MigrationRecord { fromMigrationRecord :: Git.Sha }
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-- | Logs a migration from an old to a new key.
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--
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-- This writes to a log file, which can later be committed. That allows an
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-- interrupted migration to be resumed later.
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logMigration :: MigrationRecord -> MigrationRecord -> Annex ()
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logMigration old new = do
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logf <- fromRepo gitAnnexMigrateLog
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lckf <- fromRepo gitAnnexMigrateLock
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appendLogFile logf lckf $ L.fromStrict $
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Git.fromRef' (fromMigrationRecord old)
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<> " "
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<> Git.fromRef' (fromMigrationRecord new)
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-- | Commits a migration to the git-annex branch.
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commitMigration :: Annex ()
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commitMigration = do
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logf <- fromRawFilePath <$> fromRepo gitAnnexMigrateLog
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lckf <- fromRepo gitAnnexMigrateLock
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nv <- liftIO $ newTVarIO (0 :: Integer)
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g <- Annex.gitRepo
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withMkTreeHandle g $ \oldh ->
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withMkTreeHandle g $ \newh ->
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streamLogFile logf lckf
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(finalizer nv oldh newh g)
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(processor nv oldh newh)
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where
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processor nv oldh newh s = case words s of
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(old:new:[]) -> do
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fn <- liftIO $ atomically $ do
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n <- readTVar nv
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let !n' = succ n
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writeTVar nv n'
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return (asTopFilePath (encodeBS (show n')))
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let rec h r = liftIO $ sendMkTree h
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(fromTreeItemType TreeFile)
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BlobObject
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(Git.Ref (encodeBS r))
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fn
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rec oldh old
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rec newh new
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_ -> error "migrate.log parse error"
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finalizer nv oldh newh g = do
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oldt <- liftIO $ finishMkTree oldh
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newt <- liftIO $ finishMkTree newh
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n <- liftIO $ atomically $ readTVar nv
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when (n > 0) $ do
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treesha <- liftIO $ flip recordTree g $ Tree
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[ RecordedSubTree (asTopFilePath "old") oldt []
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, RecordedSubTree (asTopFilePath "new") newt []
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]
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Annex.Branch.rememberTreeish treesha
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(asTopFilePath migrationTreeGraftPoint)
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