automatically launch git repository repair

Added a RemoteChecker thread, that waits for problems to be reported with
remotes, and checks if their git repository is in need of repair.

Currently, only failures to sync with the remote cause a problem to be
reported. This seems enough, but we'll see.

Plugging in a removable drive with a repository on it that is corrupted
does automatically repair the repository, as long as the corruption causes
git push or git pull to fail. Some types of corruption do not, eg
missing/corrupt objects for blobs that git push doesn't need to look at.

So, this is not really a replacement for scheduled git repository fscking.
But it does make the assistant more robust.

This commit is sponsored by Fernando Jimenez.

Assistant.hs

@@ -23,6 +23,7 @@ import Assistant.Threads.TransferWatcher
 import Assistant.Threads.Transferrer
 import Assistant.Threads.SanityChecker
 import Assistant.Threads.Cronner
+import Assistant.Threads.RemoteChecker
 #ifdef WITH_CLIBS
 import Assistant.Threads.MountWatcher
 #endif
@@ -129,6 +130,7 @@ startDaemon assistant foreground startdelay listenhost startbrowser = do
 			, assist $ daemonStatusThread
 			, assist $ sanityCheckerDailyThread
 			, assist $ sanityCheckerHourlyThread
+			, assist $ remoteCheckerThread urlrenderer
 #ifdef WITH_CLIBS
 			, assist $ mountWatcherThread
 #endif

Assistant/Alert.hs

@@ -19,6 +19,7 @@ import Git.Remote (RemoteName)
 
 import Data.String
 import qualified Data.Text as T
+import qualified Control.Exception as E
 
 #ifdef WITH_WEBAPP
 import Assistant.Monad
@@ -174,6 +175,17 @@ fsckAlert button n = baseActivityAlert
 	, alertButton = Just button
 	}
 
+showFscking :: UrlRenderer -> Maybe RemoteName -> IO (Either E.SomeException a) -> Assistant a
+showFscking urlrenderer remotename a = do
+#ifdef WITH_WEBAPP
+	button <- mkAlertButton False (T.pack "Configure") urlrenderer ConfigFsckR
+	r <- alertDuring (fsckAlert button remotename) $
+		liftIO a
+	either (liftIO . E.throwIO) return r
+#else
+	a
+#endif
+
 brokenRepositoryAlert :: AlertButton -> Alert
 brokenRepositoryAlert = errorAlert "Serious problems have been detected with your repository. This needs your immediate attention!"
 

Assistant/Monad.hs

@@ -39,6 +39,7 @@ import Assistant.Types.Pushes
 import Assistant.Types.BranchChange
 import Assistant.Types.Commits
 import Assistant.Types.Changes
+import Assistant.Types.RemoteProblem
 import Assistant.Types.Buddies
 import Assistant.Types.NetMessager
 import Assistant.Types.ThreadName
@@ -63,6 +64,7 @@ data AssistantData = AssistantData
 	, failedPushMap :: FailedPushMap
 	, commitChan :: CommitChan
 	, changePool :: ChangePool
+	, remoteProblemChan :: RemoteProblemChan
 	, branchChangeHandle :: BranchChangeHandle
 	, buddyList :: BuddyList
 	, netMessager :: NetMessager
@@ -80,6 +82,7 @@ newAssistantData st dstatus = AssistantData
 	<*> newFailedPushMap
 	<*> newCommitChan
 	<*> newChangePool
+	<*> newRemoteProblemChan
 	<*> newBranchChangeHandle
 	<*> newBuddyList
 	<*> newNetMessager

Assistant/RemoteProblem.hs

@@ -0,0 +1,23 @@
+{- git-annex assistant remote problem handling
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Assistant.RemoteProblem where
+
+import Assistant.Common
+import Utility.TList
+
+import Control.Concurrent.STM
+
+{- Gets all remotes that have problems.
+ - Blocks until there is at least one. -}
+getRemoteProblems :: Assistant [Remote]
+getRemoteProblems = (atomically . getTList) <<~ remoteProblemChan
+
+{- Indicates that there was a problem accessing a remote, and the problem
+ - appears to not be a transient (eg network connection) problem. -}
+remoteHasProblem :: Remote -> Assistant ()
+remoteHasProblem r  = (atomically . flip consTList r) <<~ remoteProblemChan

Assistant/Repair.hs

@@ -33,24 +33,21 @@ import Control.Concurrent.Async
 
 {- When the FsckResults require a repair, tries to do a non-destructive
  - repair. If that fails, pops up an alert. -}
-repairWhenNecessary :: UrlRenderer -> UUID -> Maybe Remote -> FsckResults -> Assistant ()
+repairWhenNecessary :: UrlRenderer -> UUID -> Maybe Remote -> FsckResults -> Assistant Bool
 repairWhenNecessary urlrenderer u mrmt fsckresults
 	| foundBroken fsckresults = do
 		liftAnnex $ writeFsckResults u fsckresults
 		repodesc <- liftAnnex $ Remote.prettyUUID u
-		handle =<< alertDuring (repairingAlert repodesc)
+		ok <- alertWhile (repairingAlert repodesc)
 			(runRepair u mrmt False)
-	| otherwise = noop
-  where
-	handle True = return ()
-	handle False = do
 #ifdef WITH_WEBAPP
-		button <- mkAlertButton True (T.pack "Click Here") urlrenderer $
-			RepairRepositoryR u
-		void $ addAlert $ brokenRepositoryAlert button
-#else
-		return ()
+		unless ok $ do
+			button <- mkAlertButton True (T.pack "Click Here") urlrenderer $
+				RepairRepositoryR u
+			void $ addAlert $ brokenRepositoryAlert button
+		return ok
 #endif
+	| otherwise = return False
 
 runRepair :: UUID -> Maybe Remote -> Bool -> Assistant Bool
 runRepair u mrmt destructiverepair = do

Assistant/Sync.hs

@@ -33,6 +33,7 @@ import Assistant.NamedThread
 import Assistant.Threads.Watcher (watchThread, WatcherControl(..))
 import Assistant.TransferSlots
 import Assistant.TransferQueue
+import Assistant.RemoteProblem
 import Logs.Transfer
 
 import Data.Time.Clock
@@ -59,11 +60,14 @@ import Control.Concurrent
 reconnectRemotes :: Bool -> [Remote] -> Assistant ()
 reconnectRemotes _ [] = noop
 reconnectRemotes notifypushes rs = void $ do
-	rs' <- filterM (checkavailable . Remote.repo) rs
+	rs' <- liftIO $ filterM (Remote.checkAvailable True) rs
 	unless (null rs') $ do
 		modifyDaemonStatus_ $ \s -> s
 			{ desynced = S.union (S.fromList $ map Remote.uuid xmppremotes) (desynced s) }
 		failedrs <- syncAction rs' (const go)
+		forM_ failedrs $ \r ->
+			whenM (liftIO $ Remote.checkAvailable False r) $
+				remoteHasProblem r
 		mapM_ signal $ filter (`notElem` failedrs) rs'
   where
 	gitremotes = filter (notspecialremote . Remote.repo) rs
@@ -90,10 +94,6 @@ reconnectRemotes notifypushes rs = void $ do
 	signal r = liftIO . mapM_ (flip tryPutMVar ())
 		=<< fromMaybe [] . M.lookup (Remote.uuid r) . connectRemoteNotifiers
 			<$> getDaemonStatus
-	checkavailable r
-		| Git.repoIsLocal r || Git.repoIsLocalUnknown r =
-			liftIO $ doesDirectoryExist $ Git.repoPath r
-		| otherwise = return True
 
 {- Updates the local sync branch, then pushes it to all remotes, in
  - parallel, along with the git-annex branch. This is the same

Assistant/Threads/Cronner.hs

@@ -5,7 +5,7 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
-{-# LANGUAGE DeriveDataTypeable, CPP #-}
+{-# LANGUAGE DeriveDataTypeable #-}
 
 module Assistant.Threads.Cronner (
 	cronnerThread
@@ -29,10 +29,6 @@ import Assistant.Types.UrlRenderer
 import Assistant.Alert
 import Remote
 import qualified Types.Remote as Remote
-#ifdef WITH_WEBAPP
-import Assistant.WebApp.Types
-#endif
-import Git.Remote (RemoteName)
 import qualified Git.Fsck
 import Assistant.Repair
 import qualified Git
@@ -43,8 +39,6 @@ import Data.Time.LocalTime
 import Data.Time.Clock
 import qualified Data.Map as M
 import qualified Data.Set as S
-import qualified Control.Exception as E
-import qualified Data.Text as T
 
 {- Loads schedules for this repository, and fires off one thread for each 
  - scheduled event that runs on this repository. Each thread sleeps until
@@ -191,7 +185,7 @@ runActivity' urlrenderer (ScheduledSelfFsck _ d) = do
 		void $ batchCommand program (Param "fsck" : annexFsckParams d)
 		Git.Fsck.findBroken True g
 	u <- liftAnnex getUUID
-	repairWhenNecessary urlrenderer u Nothing fsckresults
+	void $ repairWhenNecessary urlrenderer u Nothing fsckresults
 	mapM_ reget =<< liftAnnex (dirKeys gitAnnexBadDir)
   where
 	reget k = queueTransfers "fsck found bad file; redownloading" Next k Nothing Download
@@ -220,18 +214,7 @@ runActivity' urlrenderer (ScheduledRemoteFsck u s d) = handle =<< liftAnnex (rem
 			if Git.repoIsLocal r && not (Git.repoIsLocalUnknown r)
 				then Just <$> Git.Fsck.findBroken True r
 				else pure Nothing
-		maybe noop (repairWhenNecessary urlrenderer u (Just rmt)) fsckresults
-
-showFscking :: UrlRenderer -> Maybe RemoteName -> IO (Either E.SomeException a) -> Assistant a
-showFscking urlrenderer remotename a = do
-#ifdef WITH_WEBAPP
-	button <- mkAlertButton False (T.pack "Configure") urlrenderer ConfigFsckR
-	r <- alertDuring (fsckAlert button remotename) $
-		liftIO a
-	either (liftIO . E.throwIO) return r
-#else
-	a
-#endif
+		maybe noop (void . repairWhenNecessary urlrenderer u (Just rmt)) fsckresults
 
 annexFsckParams :: Duration -> [CommandParam]
 annexFsckParams d =

Assistant/Threads/Pusher.hs

@@ -13,6 +13,7 @@ import Assistant.Pushes
 import Assistant.DaemonStatus
 import Assistant.Sync
 import Utility.ThreadScheduler
+import qualified Remote
 import qualified Types.Remote as Remote
 
 {- This thread retries pushes that failed before. -}
@@ -42,7 +43,7 @@ pushThread = namedThread "Pusher" $ runEvery (Seconds 2) <~> do
  - to avoid ugly messages when a removable drive is not attached.
  -}
 pushTargets :: Assistant [Remote]
-pushTargets = liftIO . filterM available =<< candidates <$> getDaemonStatus
+pushTargets = liftIO . filterM (Remote.checkAvailable True)
+	=<< candidates <$> getDaemonStatus
   where
 	candidates = filter (not . Remote.readonly) . syncGitRemotes
-	available = maybe (return True) doesDirectoryExist . Remote.localpath

Assistant/Threads/RemoteChecker.hs

@@ -0,0 +1,46 @@
+{- git-annex assistant remote checker thread
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Assistant.Threads.RemoteChecker (
+	remoteCheckerThread
+) where
+
+import Assistant.Common
+import Utility.ThreadScheduler
+import Assistant.Types.UrlRenderer
+import Assistant.Alert
+import Remote
+import qualified Types.Remote as Remote
+import qualified Git.Fsck
+import Assistant.Repair
+import qualified Git
+import Assistant.RemoteProblem
+import Assistant.Sync
+
+import Data.Function
+
+{- Waits for problems with remotes, and tries to fsck the remote and repair
+ - the problem. -}
+remoteCheckerThread :: UrlRenderer -> NamedThread
+remoteCheckerThread urlrenderer = namedThread "RemoteChecker" $ forever $ do
+	mapM_ (handleProblem urlrenderer)
+		=<< liftIO . filterM (checkAvailable True)
+		=<< nubremotes <$> getRemoteProblems
+	liftIO $ threadDelaySeconds (Seconds 60)
+  where
+	nubremotes = nubBy ((==) `on` Remote.uuid)
+
+handleProblem :: UrlRenderer -> Remote -> Assistant ()
+handleProblem urlrenderer rmt
+	| Git.repoIsLocal r && not (Git.repoIsLocalUnknown r) = do
+		fsckresults <- showFscking urlrenderer (Just $ Remote.name rmt) $ tryNonAsync $
+			Git.Fsck.findBroken True r
+		whenM (repairWhenNecessary urlrenderer (Remote.uuid rmt) (Just rmt) fsckresults) $
+			syncRemote rmt
+	| otherwise = noop
+  where
+	r = Remote.repo rmt

Assistant/Types/RemoteProblem.hs

@@ -0,0 +1,18 @@
+{- git-annex assistant remote problem detection
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Assistant.Types.RemoteProblem where
+
+import Types
+import Utility.TList
+
+import Control.Concurrent.STM
+
+type RemoteProblemChan = TList Remote
+
+newRemoteProblemChan :: IO RemoteProblemChan
+newRemoteProblemChan = atomically newTList

Remote.hs

@@ -39,7 +39,8 @@ module Remote (
 	showTriedRemotes,
 	showLocations,
 	forceTrust,
-	logStatus
+	logStatus,
+	checkAvailable
 ) where
 
 import qualified Data.Map as M
@@ -274,3 +275,7 @@ byCost = map snd . sortBy (comparing fst) . M.toList . costmap
   where
 	costmap = M.fromListWith (++) . map costpair
 	costpair r = (cost r, [r])
+
+checkAvailable :: Bool -> Remote -> IO Bool
+checkAvailable assumenetworkavailable = 
+	maybe (return assumenetworkavailable) doesDirectoryExist . localpath