1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
{- Waiting for changed git refs
-
- Copyright 2014-216 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Annex.ChangedRefs
( ChangedRefs(..)
, ChangedRefsHandle
, waitChangedRefs
, drainChangedRefs
, stopWatchingChangedRefs
, watchChangedRefs
) where
import Annex.Common
import Utility.DirWatcher
import Utility.DirWatcher.Types
import qualified Git
import Git.Sha
import qualified Utility.SimpleProtocol as Proto
import Control.Concurrent
import Control.Concurrent.STM
import Control.Concurrent.STM.TBMChan
newtype ChangedRefs = ChangedRefs [Git.Ref]
deriving (Show)
instance Proto.Serializable ChangedRefs where
serialize (ChangedRefs l) = unwords $ map Git.fromRef l
deserialize = Just . ChangedRefs . map Git.Ref . words
data ChangedRefsHandle = ChangedRefsHandle DirWatcherHandle (TBMChan Git.Sha)
-- | Wait for one or more git refs to change.
--
-- When possible, coalesce ref writes that occur closely together
-- in time. Delay up to 0.05 seconds to get more ref writes.
waitChangedRefs :: ChangedRefsHandle -> IO ChangedRefs
waitChangedRefs (ChangedRefsHandle _ chan) =
atomically (readTBMChan chan) >>= \case
Nothing -> return $ ChangedRefs []
Just r -> do
threadDelay 50000
rs <- atomically $ loop []
return $ ChangedRefs (r:rs)
where
loop rs = tryReadTBMChan chan >>= \case
Just (Just r) -> loop (r:rs)
_ -> return rs
-- | Remove any changes that might be buffered in the channel,
-- without waiting for any new changes.
drainChangedRefs :: ChangedRefsHandle -> IO ()
drainChangedRefs (ChangedRefsHandle _ chan) = atomically go
where
go = tryReadTBMChan chan >>= \case
Just (Just _) -> go
_ -> return ()
stopWatchingChangedRefs :: ChangedRefsHandle -> IO ()
stopWatchingChangedRefs h@(ChangedRefsHandle wh chan) = do
stopWatchDir wh
atomically $ closeTBMChan chan
drainChangedRefs h
watchChangedRefs :: Annex (Maybe ChangedRefsHandle)
watchChangedRefs = do
-- This channel is used to accumulate notifications,
-- because the DirWatcher might have multiple threads that find
-- changes at the same time. It is bounded to allow a watcher
-- to be started once and reused, without too many changes being
-- buffered in memory.
chan <- liftIO $ newTBMChanIO 100
g <- gitRepo
let refdir = Git.localGitDir g </> "refs"
liftIO $ createDirectoryIfMissing True refdir
let notifyhook = Just $ notifyHook chan
let hooks = mkWatchHooks
{ addHook = notifyhook
, modifyHook = notifyhook
}
if canWatch
then do
h <- liftIO $ watchDir refdir (const False) True hooks id
return $ Just $ ChangedRefsHandle h chan
else return Nothing
notifyHook :: TBMChan Git.Sha -> FilePath -> Maybe FileStatus -> IO ()
notifyHook chan reffile _
| ".lock" `isSuffixOf` reffile = noop
| otherwise = void $ do
sha <- catchDefaultIO Nothing $
extractSha <$> readFile reffile
-- When the channel is full, there is probably no reader
-- running, or ref changes have been occuring very fast,
-- so it's ok to not write the change to it.
maybe noop (void . atomically . tryWriteTBMChan chan) sha
|
