git-annex/Assistant/Threads/PushNotifier.hs

{- git-annex assistant push notification thread, using XMPP
 -
 - This handles both sending outgoing push notifications, and receiving
 - incoming push notifications.
 -
 - Copyright 2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Assistant.Threads.PushNotifier where

import Assistant.Common
import Assistant.XMPP
import Assistant.DaemonStatus
import Assistant.Pushes
import Assistant.Sync
import qualified Remote
import Utility.ThreadScheduler

import Network.Protocol.XMPP
import Control.Concurrent
import qualified Data.Set as S
import qualified Git.Branch
import Data.Time.Clock

pushNotifierThread :: NamedThread
pushNotifierThread = NamedThread "PushNotifier" $ do
	iodebug <- asIO debug
	iopull <- asIO pull
	iowaitpush <- asIO $ const waitPush
	ioclient <- asIO2 $ xmppClient $ iowaitpush ()
	forever $ do
		tid <- liftIO $ forkIO $ ioclient iodebug iopull
		waitRestart
		liftIO $ killThread tid

xmppClient :: (IO [UUID]) -> ([String] -> IO ()) -> ([UUID] -> IO ()) -> Assistant ()
xmppClient iowaitpush iodebug iopull = do
	v <- liftAnnex getXMPPCreds
	case v of
		Nothing -> noop
		Just c -> liftIO $ loop c =<< getCurrentTime
  where
	loop c starttime = do
		void $ connectXMPP c $ \jid -> do
			fulljid <- bindJID jid
			liftIO $ iodebug ["XMPP connected", show fulljid]
			putStanza $ gitAnnexPresence gitAnnexSignature
			s <- getSession
			_ <- liftIO $ forkIO $ void $ runXMPP s $
				receivenotifications
			sendnotifications
		now <- getCurrentTime
		if diffUTCTime now starttime > 300
			then do
				iodebug ["XMPP connection lost; reconnecting"]
				loop c now
			else do
				iodebug ["XMPP connection failed; will retry"]
				threadDelaySeconds (Seconds 300)
				loop c =<< getCurrentTime
	sendnotifications = forever $ do
		us <- liftIO iowaitpush
		putStanza $ gitAnnexPresence $ encodePushNotification us
	receivenotifications = forever $ do
		s <- getStanza
		liftIO $ iodebug ["received XMPP:", show s]
		case s of
			ReceivedPresence p@(Presence { presenceType = PresenceAvailable }) ->
				liftIO $ iopull $ concat $ catMaybes $
					map decodePushNotification $
						presencePayloads p
			_ -> noop

{- We only pull from one remote out of the set listed in the push
 - notification, as an optimisation.
 -
 - Note that it might be possible (though very unlikely) for the push
 - notification to take a while to be sent, and multiple pushes happen
 - before it is sent, so it includes multiple remotes that were pushed
 - to at different times. 
 -
 - It could then be the case that the remote we choose had the earlier
 - push sent to it, but then failed to get the later push, and so is not
 - fully up-to-date. If that happens, the pushRetryThread will come along
 - and retry the push, and we'll get another notification once it succeeds,
 - and pull again. -}
pull :: [UUID] -> Assistant ()
pull [] = noop
pull us = do
	rs <- filter matching . syncRemotes <$> daemonStatus
	debug $ "push notification for" : map (fromUUID . Remote.uuid ) rs
	pullone rs =<< liftAnnex (inRepo Git.Branch.current)
  where
	matching r = Remote.uuid r `S.member` s
	s = S.fromList us

	pullone [] _ = noop
	pullone (r:rs) branch =
		unlessM (all id . fst <$> manualPull branch [r]) $
			pullone rs branch