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{- higher-level inotify interface
-
- Copyright 2012 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
module Utility.DirWatcher.INotify where
import Common hiding (isDirectory)
import Utility.ThreadLock
import Utility.DirWatcher.Types
import System.INotify
import qualified System.Posix.Files as Files
import System.IO.Error
import Control.Exception (throw)
{- Watches for changes to files in a directory, and all its subdirectories
- that are not ignored, using inotify. This function returns after
- its initial scan is complete, leaving a thread running. Callbacks are
- made for different events.
-
- Inotify is weak at recursive directory watching; the whole directory
- tree must be scanned and watches set explicitly for each subdirectory.
-
- To notice newly created subdirectories, inotify is used, and
- watches are registered for those directories. There is a race there;
- things can be added to a directory before the watch gets registered.
-
- To close the inotify race, each time a new directory is found, it also
- recursively scans it, assuming all files in it were just added,
- and registering each subdirectory.
-
- Note: Due to the race amelioration, multiple add events may occur
- for the same file.
-
- Note: Moving a file will cause events deleting it from its old location
- and adding it to the new location.
-
- Note: It's assumed that when a file that was open for write is closed,
- it's finished being written to, and can be added.
-
- Note: inotify has a limit to the number of watches allowed,
- /proc/sys/fs/inotify/max_user_watches (default 8192).
- So this will fail if there are too many subdirectories. The
- errHook is called when this happens.
-}
watchDir :: INotify -> FilePath -> (FilePath -> Bool) -> Bool -> WatchHooks -> IO ()
watchDir i dir ignored scanevents hooks
| ignored dir = noop
| otherwise = do
-- Use a lock to make sure events generated during initial
-- scan come before real inotify events.
lock <- newLock
let handler event = withLock lock (void $ go event)
flip catchNonAsync failedwatch $ do
void (addWatch i watchevents dir handler)
`catchIO` failedaddwatch
withLock lock $
mapM_ scan =<< filter (not . dirCruft) <$>
getDirectoryContents dir
where
recurse d = watchDir i d ignored scanevents hooks
-- Select only inotify events required by the enabled
-- hooks, but always include Create so new directories can
-- be scanned.
watchevents = Create : addevents ++ delevents ++ modifyevents
addevents
| hashook addHook || hashook addSymlinkHook = [MoveIn, CloseWrite]
| otherwise = []
delevents
| hashook delHook || hashook delDirHook = [MoveOut, Delete]
| otherwise = []
modifyevents
| hashook modifyHook = [Modify]
| otherwise = []
scan f = unless (ignored f) $ do
ms <- getstatus f
case ms of
Nothing -> return ()
Just s
| Files.isDirectory s ->
recurse $ indir f
| Files.isSymbolicLink s ->
when scanevents $
runhook addSymlinkHook f ms
| Files.isRegularFile s ->
when scanevents $
runhook addHook f ms
| otherwise ->
noop
go (Created { isDirectory = isd, filePath = f })
| isd = recurse $ indir f
| otherwise = do
ms <- getstatus f
case ms of
Just s
| Files.isSymbolicLink s ->
when (hashook addSymlinkHook) $
runhook addSymlinkHook f ms
| Files.isRegularFile s ->
when (hashook addHook) $
runhook addHook f ms
_ -> noop
-- Closing a file is assumed to mean it's done being written,
-- so a new add event is sent.
go (Closed { isDirectory = False, maybeFilePath = Just f }) =
checkfiletype Files.isRegularFile addHook f
-- When a file or directory is moved in, scan it to add new
-- stuff.
go (MovedIn { filePath = f }) = scan f
go (MovedOut { isDirectory = isd, filePath = f })
| isd = runhook delDirHook f Nothing
| otherwise = runhook delHook f Nothing
-- Verify that the deleted item really doesn't exist,
-- since there can be spurious deletion events for items
-- in a directory that has been moved out, but is still
-- being watched.
go (Deleted { isDirectory = isd, filePath = f })
| isd = guarded $ runhook delDirHook f Nothing
| otherwise = guarded $ runhook delHook f Nothing
where
guarded = unlessM (filetype (const True) f)
go (Modified { isDirectory = isd, maybeFilePath = Just f })
| isd = noop
| otherwise = runhook modifyHook f Nothing
go _ = noop
hashook h = isJust $ h hooks
runhook h f s
| ignored f = noop
| otherwise = maybe noop (\a -> a (indir f) s) (h hooks)
indir f = dir </> f
getstatus f = catchMaybeIO $ getSymbolicLinkStatus $ indir f
checkfiletype check h f = do
ms <- getstatus f
case ms of
Just s
| check s -> runhook h f ms
_ -> noop
filetype t f = catchBoolIO $ t <$> getSymbolicLinkStatus (indir f)
failedaddwatch e
-- Inotify fails when there are too many watches with a
-- disk full error.
| isFullError e =
case errHook hooks of
Nothing -> error $ "failed to add inotify watch on directory " ++ dir ++ " (" ++ show e ++ ")"
Just hook -> tooManyWatches hook dir
-- The directory could have been deleted.
| isDoesNotExistError e = return ()
| otherwise = throw e
failedwatch e = hPutStrLn stderr $ "failed to add watch on directory " ++ dir ++ " (" ++ show e ++ ")"
tooManyWatches :: (String -> Maybe FileStatus -> IO ()) -> FilePath -> IO ()
tooManyWatches hook dir = do
sysctlval <- querySysctl [Param maxwatches] :: IO (Maybe Integer)
hook (unlines $ basewarning : maybe withoutsysctl withsysctl sysctlval) Nothing
where
maxwatches = "fs.inotify.max_user_watches"
basewarning = "Too many directories to watch! (Not watching " ++ dir ++")"
withoutsysctl = ["Increase the value in /proc/sys/fs/inotify/max_user_watches"]
withsysctl n = let new = n * 10 in
[ "Increase the limit permanently by running:"
, " echo " ++ maxwatches ++ "=" ++ show new ++
" | sudo tee -a /etc/sysctl.conf; sudo sysctl -p"
, "Or temporarily by running:"
, " sudo sysctl -w " ++ maxwatches ++ "=" ++ show new
]
querySysctl :: Read a => [CommandParam] -> IO (Maybe a)
querySysctl ps = getM go ["sysctl", "/sbin/sysctl", "/usr/sbin/sysctl"]
where
go p = do
v <- catchMaybeIO $ readProcess p (toCommand ps)
case v of
Nothing -> return Nothing
Just s -> return $ parsesysctl s
parsesysctl s = readish =<< lastMaybe (words s)
|
