per-remote metadata storage

Actually very straightforward reuse of the metadata log file code.
Although I had to add a todo item as git-annex forget won't clean up
dead remote's metadata yet.

This would be worth adding to the external special remote interface
sometime. Have not opened a todo though, guess I'll wait until something
needs it.

This commit was supported by the NSF-funded DataLad project.

Command/MetaData.hs

@@ -112,7 +112,7 @@ perform c o k = case getSet o of
 	Set ms -> do
 		oldm <- getCurrentMetaData k
 		let m = combineMetaData $ map (modMeta oldm) ms
-		addMetaData' k m c
+		addMetaDataClocked k m c
 		next $ cleanup k
 	_ -> next $ cleanup k
 

Logs.hs

@@ -1,6 +1,6 @@
 {- git-annex log file names
  -
- - Copyright 2013-2015 Joey Hess <id@joeyh.name>
+ - Copyright 2013-2018 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -26,7 +26,7 @@ getLogVariety f
 	| f `elem` topLevelUUIDBasedLogs = Just UUIDBasedLog
 	| isRemoteStateLog f = Just NewUUIDBasedLog
 	| isChunkLog f = ChunkLog <$> chunkLogFileKey f
-	| isMetaDataLog f || f `elem` otherLogs = Just OtherLog
+	| isMetaDataLog f || isRemoteMetaDataLog f || f `elem` otherLogs = Just OtherLog
 	| otherwise = PresenceLog <$> firstJust (presenceLogs f)
 
 {- All the uuid-based logs stored in the top of the git-annex branch. -}
@@ -185,3 +185,13 @@ metaDataLogExt = ".log.met"
 
 isMetaDataLog :: FilePath -> Bool
 isMetaDataLog path = metaDataLogExt `isSuffixOf` path
+
+{- The filename of the remote metadata log for a given key. -}
+remoteMetaDataLogFile :: GitConfig -> Key -> FilePath
+remoteMetaDataLogFile config key = branchHashDir config key </> keyFile key ++ remoteMetaDataLogExt
+
+remoteMetaDataLogExt :: String
+remoteMetaDataLogExt = ".log.rmet"
+
+isRemoteMetaDataLog :: FilePath -> Bool
+isRemoteMetaDataLog path = remoteMetaDataLogExt `isSuffixOf` path

Logs/MetaData.hs

@@ -1,7 +1,9 @@
-{- git-annex general metadata storage log
+{- git-annex general metadata storage log and per-remote metadata storage log.
  -
  - A line of the log will look like "timestamp field [+-]value [...]"
  -
+ - (In the per-remote log, each field is prefixed with "uuid:")
+ -
  - Note that unset values are preserved. Consider this case:
  -
  - We have:
@@ -18,7 +20,7 @@
  - and so foo currently has no value.
  -
  -
- - Copyright 2014 Joey Hess <id@joeyh.name>
+ - Copyright 2014-2018 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -27,8 +29,10 @@
 
 module Logs.MetaData (
 	getCurrentMetaData,
+	getCurrentRemoteMetaData,
 	addMetaData,
-	addMetaData',
+	addRemoteMetaData,
+	addMetaDataClocked,
 	currentMetaData,
 	copyMetaData,
 ) where
@@ -50,11 +54,6 @@ instance SingleValueSerializable MetaData where
 	serialize = Types.MetaData.serialize
 	deserialize = Types.MetaData.deserialize
 
-getMetaDataLog :: Key -> Annex (Log MetaData)
-getMetaDataLog key = do
-	config <- Annex.getGitConfig
-	readLog $ metaDataLogFile config key
-
 logToCurrentMetaData :: [LogEntry MetaData] -> MetaData
 logToCurrentMetaData = currentMetaData . combineMetaData . map value
 
@@ -65,8 +64,12 @@ logToCurrentMetaData = currentMetaData . combineMetaData . map value
  - currently set, based on timestamps in the log.
  -}
 getCurrentMetaData :: Key -> Annex MetaData
-getCurrentMetaData k = do
+getCurrentMetaData = getCurrentMetaData' metaDataLogFile
-	ls <- S.toAscList <$> getMetaDataLog k
+
+getCurrentMetaData' :: (GitConfig -> Key -> FilePath) -> Key -> Annex MetaData
+getCurrentMetaData' getlogfile k = do
+	config <- Annex.getGitConfig
+	ls <- S.toAscList <$> readLog (getlogfile config k)
 	let loggedmeta = logToCurrentMetaData ls
 	return $ currentMetaData $ unionMetaData loggedmeta
 		(lastchanged ls loggedmeta)
@@ -92,27 +95,42 @@ getCurrentMetaData k = do
 			Unknown -> 0
 	showts = formatPOSIXTime "%F@%H-%M-%S"
 
+getCurrentRemoteMetaData :: UUID -> Key -> Annex RemoteMetaData
+getCurrentRemoteMetaData u k = mkRemoteMetaData u <$>
+	getCurrentMetaData' remoteMetaDataLogFile k
+
 {- Adds in some metadata, which can override existing values, or unset
  - them, but otherwise leaves any existing metadata as-is. -}
 addMetaData :: Key -> MetaData -> Annex ()
-addMetaData k metadata = addMetaData' k metadata =<< liftIO currentVectorClock
+addMetaData = addMetaData' metaDataLogFile
+
+addMetaData' :: (GitConfig -> Key -> FilePath) -> Key -> MetaData -> Annex ()
+addMetaData' getlogfile k metadata = 
+	addMetaDataClocked' getlogfile k metadata =<< liftIO currentVectorClock
 
 {- Reusing the same VectorClock when making changes to the metadata
  - of multiple keys is a nice optimisation. The same metadata lines
  - will tend to be generated across the different log files, and so
  - git will be able to pack the data more efficiently. -}
-addMetaData' :: Key -> MetaData -> VectorClock -> Annex ()
+addMetaDataClocked :: Key -> MetaData -> VectorClock -> Annex ()
-addMetaData' k d@(MetaData m) c
+addMetaDataClocked = addMetaDataClocked' metaDataLogFile
+
+addMetaDataClocked' :: (GitConfig -> Key -> FilePath) -> Key -> MetaData -> VectorClock -> Annex ()
+addMetaDataClocked' getlogfile k d@(MetaData m) c
 	| d == emptyMetaData = noop
 	| otherwise = do
 		config <- Annex.getGitConfig
-		Annex.Branch.change (metaDataLogFile config k) $
+		Annex.Branch.change (getlogfile config k) $
 			showLog . simplifyLog 
 				. S.insert (LogEntry c metadata)
 				. parseLog
   where
 	metadata = MetaData $ M.filterWithKey (\f _ -> not (isLastChangedField f)) m
 
+addRemoteMetaData :: Key -> RemoteMetaData -> Annex ()
+addRemoteMetaData k m = do
+	addMetaData' remoteMetaDataLogFile k (fromRemoteMetaData m)
+
 {- Simplify a log, removing historical values that are no longer
  - needed. 
  -
@@ -173,6 +191,11 @@ simplifyLog s = case sl of
 		older = value l
 		unique = older `differenceMetaData` newer
 
+getMetaDataLog :: Key -> Annex (Log MetaData)
+getMetaDataLog key = do
+	config <- Annex.getGitConfig
+	readLog $ metaDataLogFile config key
+
 {- Copies the metadata from the old key to the new key.
  -
  - The exact content of the metadata file is copied, so that the timestamps

Types/MetaData.hs

@@ -1,6 +1,6 @@
 {- git-annex general metadata
  -
- - Copyright 2014 Joey Hess <id@joeyh.name>
+ - Copyright 2014-2018 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -36,6 +36,9 @@ module Types.MetaData (
 	metaDataValues,
 	ModMeta(..),
 	modMeta,
+	RemoteMetaData(..),
+	mkRemoteMetaData,
+	fromRemoteMetaData,
 	prop_metadata_sane,
 	prop_metadata_serialize
 ) where
@@ -44,6 +47,7 @@ import Common
 import Utility.Base64
 import Utility.QuickCheck
 import Utility.Aeson
+import Types.UUID
 
 import qualified Data.Text as T
 import qualified Data.Set as S
@@ -282,6 +286,31 @@ modMeta m (MaybeSetMeta f v)
 	| otherwise = emptyMetaData
 modMeta m (ComposeModMeta a b) = unionMetaData (modMeta m a) (modMeta m b)
 
+data RemoteMetaData = RemoteMetaData UUID MetaData
+	deriving (Show, Eq, Ord)
+
+{- Extracts only the fields prefixed with "uuid:", which belong to that
+ - remote. -}
+mkRemoteMetaData :: UUID -> MetaData -> RemoteMetaData
+mkRemoteMetaData u (MetaData m) = RemoteMetaData u $ MetaData $
+	M.mapKeys removeprefix $ M.filterWithKey belongsremote m
+  where
+	belongsremote (MetaField f) _v = prefix `isPrefixOf` CI.original f
+	removeprefix (MetaField f) = MetaField $ 
+		CI.mk $ drop prefixlen $ CI.original f
+	prefix = remoteMetaDataPrefix u
+	prefixlen = length prefix
+
+remoteMetaDataPrefix :: UUID -> String
+remoteMetaDataPrefix u = fromUUID u ++ ":"
+
+fromRemoteMetaData :: RemoteMetaData -> MetaData
+fromRemoteMetaData (RemoteMetaData u (MetaData m)) = MetaData $
+	M.mapKeys addprefix m
+  where
+	addprefix (MetaField f) = MetaField $ CI.mk $ (++ prefix) $ CI.original f
+	prefix = remoteMetaDataPrefix u
+
 {- Avoid putting too many fields in the map; extremely large maps make
  - the seriaization test slow due to the sheer amount of data.
  - It's unlikely that more than 100 fields of metadata will be used. -}

doc/internals.mdwn

@@ -236,6 +236,10 @@ These log files are used by remotes that need to record their own state
 about keys. Each remote can store one line of data about a key, in
 its own format.
 
+Note that only the most recently set state about a key is seen
+by remotes using this. The `log.rmet` documented below does not have this
+limitation.
+
 Example:
 
 	1287290776.765152s e605dca6-446a-11e0-8b2a-002170d25c55 blah blah
@@ -262,6 +266,20 @@ reasonably short. If the value contains any whitespace
 (including \r or \n), it will be base64 encoded. Base64 encoded values
 are indicated by prefixing them with "!".
 
+## `aaa/bbb/*.log.rmet`
+
+These log files store per-remote metadata about keys. This metadata
+is only used by the remote.
+
+Format is the same as the metadata log files above, but each metadata key
+is prefixed with "uuid:" to indicate the remote it belongs to.
+
+For example:
+
+	1287290776.765152s e605dca6-446a-11e0-8b2a-002170d25c55:foo +bar
+	1287290776.765152s 26339d22-446b-11e0-9101-002170d25c55:x +1
+	1291237510.141453s 26339d22-446b-11e0-9101-002170d25c55:x -1 26339d22-446b-11e0-9101-002170d25c55:x +2
+
 ## `aaa/bbb/*.log.cnk`
 
 These log files are used when objects are stored in chunked form on

doc/todo/per-remote_metadata_needs_to_be_cleaned_in_dropdead.mdwn

@@ -0,0 +1,2 @@
+The newly added per-remote metadata log files need to be scrubbed clean of
+dead remotes during a transition. --[[Joey]]