keep track of which remotes have been scanned in process state

Since it turned out to make sense to always scan all remotes on startup,
there's no need to persist the info about which have been scanned.

Assistant/Threads/TransferScanner.hs

@@ -21,6 +21,8 @@ import qualified Git.LsFiles as LsFiles
 import Command
 import Annex.Content
 
+import qualified Data.Set as S
+
 thisThread :: ThreadName
 thisThread = "TransferScanner"
 
@@ -30,16 +32,20 @@ thisThread = "TransferScanner"
 transferScannerThread :: ThreadState -> DaemonStatusHandle -> ScanRemoteMap -> TransferQueue -> IO ()
 transferScannerThread st dstatus scanremotes transferqueue = do
 	startupScan
-	runEvery (Seconds 2) $ do
-		(r, info) <- getScanRemote scanremotes
-		scanned <- runThreadState st $ inRepo $
-			checkTransferScanned $ Remote.uuid r
-		if not scanned || fullScan info
-			then expensiveScan st dstatus transferqueue r
-			else failedTransferScan st dstatus transferqueue r
+	go S.empty
 	where
-		{- All remotes are scanned in full on startup, for multiple
-		 - reasons, including:
+		go scanned = do
+			threadDelaySeconds (Seconds 2)
+			(r, info) <- getScanRemote scanremotes
+			if fullScan info || not (S.member r scanned)
+				then do
+					expensiveScan st dstatus transferqueue r
+					go (S.insert r scanned)
+				else do
+					failedTransferScan st dstatus transferqueue r
+					go scanned
+		{- All available remotes are scanned in full on startup,
+		 - for multiple reasons, including:
 		 -
 		 - * This may be the first run, and there may be remotes
 		 -   already in place, that need to be synced.
@@ -49,17 +55,9 @@ transferScannerThread st dstatus scanremotes transferqueue = do
 		 - * We may have run before, and had transfers queued,
 		 -   and then the system (or us) crashed, and that info was
 		 -   lost.
-		 -
-		 - But not all remotes may be available now. So all
-		 - prior indications that remotes have been scanned
-		 - are first removed.
 		 -}
-		startupScan = do
-			void $ tryIO $ 
-				removeDirectoryRecursive
-					=<< runThreadState st (fromRepo transferScannedDir)
-			addScanRemotes scanremotes True
-				=<< knownRemotes <$> getDaemonStatus dstatus
+		startupScan = addScanRemotes scanremotes True
+			=<< knownRemotes <$> getDaemonStatus dstatus
 
 {- This is a cheap scan for failed transfers involving a remote. -}
 failedTransferScan :: ThreadState -> DaemonStatusHandle -> TransferQueue -> Remote -> IO ()
@@ -104,8 +102,6 @@ expensiveScan st dstatus transferqueue r = do
 		g <- runThreadState st $ fromRepo id
 		files <- LsFiles.inRepo [] g
 		go files
-		runThreadState st $ inRepo $
-			transferScanned $ Remote.uuid r
 		return True
 	liftIO $ debug thisThread ["finished scan of", show r]
 	where

Logs/Transfer.hs

@@ -230,23 +230,3 @@ failedTransferDir u direction r = gitAnnexTransferDir r
 	</> "failed"
 	</> showLcDirection direction
 	</> fromUUID u
-
-{- The directory holding remote uuids that have been scanned for transfers. -}
-transferScannedDir :: Git.Repo -> FilePath
-transferScannedDir r = gitAnnexTransferDir r </> "scanned"
-
-{- The file indicating whether a remote uuid has been scanned. -}
-transferScannedFile :: UUID -> Git.Repo -> FilePath
-transferScannedFile u r = transferScannedDir r </> fromUUID u 
-
-{- Checks if a given remote UUID has been scanned for transfers. -}
-checkTransferScanned :: UUID -> Git.Repo -> IO Bool
-checkTransferScanned u r = doesFileExist $ transferScannedFile u r
-
-{- Records that a scan has taken place. -}
-transferScanned :: UUID -> Git.Repo -> IO ()
-transferScanned u r = do
-	createDirectoryIfMissing True (parentDir f)
-	writeFile f ""
-	where
-		f = transferScannedFile u r