git-annex/Assistant/Threads/Merger.hs
Joey Hess c7c2015435 add ConfigMonitor thread
Monitors git-annex branch for changes, which are noticed by the Merger
thread whenever the branch ref is changed (either due to an incoming push,
or a local change), and refreshes cached config values for modified config
files.

Rate limited to run no more often than once per minute. This is important
because frequent git-annex branch changes happen when files are being
added, or transferred, etc.

A primary use case is that, when preferred content changes are made,
and get pushed to remotes, the remotes start honoring those settings.
Other use cases include propigating repository description and trust
changes to remotes, and learning when a remote has added a new special
remote, so the webapp can present the GUI to enable that special remote
locally.

Also added a uuid.log cache. All other config files already had caches.
2012-10-20 16:43:35 -04:00

107 lines
3.4 KiB
Haskell

{- git-annex assistant git merge thread
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.Threads.Merger where
import Assistant.Common
import Assistant.ThreadedMonad
import Assistant.DaemonStatus
import Assistant.TransferQueue
import Assistant.BranchChange
import Utility.DirWatcher
import Utility.Types.DirWatcher
import qualified Annex.Branch
import qualified Git
import qualified Git.Merge
import qualified Git.Branch
thisThread :: ThreadName
thisThread = "Merger"
{- This thread watches for changes to .git/refs/, and handles incoming
- pushes. -}
mergeThread :: ThreadState -> DaemonStatusHandle -> TransferQueue -> BranchChangeHandle -> NamedThread
mergeThread st dstatus transferqueue branchchange = thread $ do
g <- runThreadState st gitRepo
let dir = Git.localGitDir g </> "refs"
createDirectoryIfMissing True dir
let hook a = Just $ runHandler st dstatus transferqueue branchchange a
let hooks = mkWatchHooks
{ addHook = hook onAdd
, errHook = hook onErr
}
void $ watchDir dir (const False) hooks id
debug thisThread ["watching", dir]
where
thread = NamedThread thisThread
type Handler = ThreadState -> DaemonStatusHandle -> TransferQueue -> BranchChangeHandle -> FilePath -> Maybe FileStatus -> IO ()
{- Runs an action handler.
-
- Exceptions are ignored, otherwise a whole thread could be crashed.
-}
runHandler :: ThreadState -> DaemonStatusHandle -> TransferQueue -> BranchChangeHandle -> Handler -> FilePath -> Maybe FileStatus -> IO ()
runHandler st dstatus transferqueue branchchange handler file filestatus = void $
either print (const noop) =<< tryIO go
where
go = handler st dstatus transferqueue branchchange file filestatus
{- Called when there's an error with inotify. -}
onErr :: Handler
onErr _ _ _ _ msg _ = error msg
{- Called when a new branch ref is written.
-
- This relies on git's atomic method of updating branch ref files,
- which is to first write the new file to .lock, and then rename it
- over the old file. So, ignore .lock files, and the rename ensures
- the watcher sees a new file being added on each update.
-
- At startup, synthetic add events fire, causing this to run, but that's
- ok; it ensures that any changes pushed since the last time the assistant
- ran are merged in.
-}
onAdd :: Handler
onAdd st dstatus transferqueue branchchange file _
| ".lock" `isSuffixOf` file = noop
| isAnnexBranch file = do
branchChanged branchchange
runThreadState st $
whenM Annex.Branch.forceUpdate $
queueDeferredDownloads Later transferqueue dstatus
| "/synced/" `isInfixOf` file = runThreadState st $ do
mergecurrent =<< inRepo Git.Branch.current
| otherwise = noop
where
changedbranch = fileToBranch file
mergecurrent (Just current)
| equivBranches changedbranch current = do
liftIO $ debug thisThread
[ "merging"
, show changedbranch
, "into"
, show current
]
void $ inRepo $
Git.Merge.mergeNonInteractive changedbranch
mergecurrent _ = noop
equivBranches :: Git.Ref -> Git.Ref -> Bool
equivBranches x y = base x == base y
where
base = takeFileName . show
isAnnexBranch :: FilePath -> Bool
isAnnexBranch f = n `isSuffixOf` f
where
n = "/" ++ show Annex.Branch.name
fileToBranch :: FilePath -> Git.Ref
fileToBranch f = Git.Ref $ "refs" </> base
where
base = Prelude.last $ split "/refs/" f