daemons (empty) → 0.1.0
raw patch · 15 files changed
+1670/−0 lines, 15 filesdep +HUnitdep +basedep +bytestringsetup-changed
Dependencies added: HUnit, base, bytestring, cereal, containers, data-default, directory, filepath, ghc-prim, network, pipes, test-framework, test-framework-hunit, transformers, unix
Files
- AddOne.hs +15/−0
- Control/Pipe/C3.hs +40/−0
- Control/Pipe/Serialize.hs +48/−0
- Control/Pipe/Socket.hs +79/−0
- LICENSE +675/−0
- Makefile +25/−0
- Memo.hs +59/−0
- NEWS.md +0/−0
- PMTQ.hs +98/−0
- README.md +80/−0
- Setup.hs +2/−0
- System/Daemon.hs +156/−0
- System/Posix/Daemon.hs +191/−0
- Test/Daemon.hs +122/−0
- daemons.cabal +80/−0
+ AddOne.hs view
@@ -0,0 +1,15 @@+module Main where++import Data.Default ( def )+import System.Environment ( getArgs )+import System.Daemon++addOne :: Int -> IO Int+addOne n = return (n + 1)++main :: IO ()+main = do+ startDaemon "addOne" def addOne+ [n] <- getArgs+ res <- runClient "localhost" 5000 ((read n) :: Int)+ print (res :: Maybe Int)
+ Control/Pipe/C3.hs view
@@ -0,0 +1,40 @@+module Control.Pipe.C3 (+ -- * Pipes+ commandSender, commandReceiver+ ) where++import Control.Monad ( forever )+import Control.Monad.Trans.Class ( lift )+import Control.Pipe ( runPipe, await, yield, (<+<) )+import Control.Pipe.Serialize ( serializer, deserializer )+import Control.Pipe.Socket ( Handler )+import Data.Serialize ( Serialize )++-- | Send a single command over the outgoing pipe and wait for a+-- response. If the incoming pipe is closed before a response+-- arrives, returns @Nothing@.+commandSender :: (Serialize a, Serialize b) => a -> Handler (Maybe b)+commandSender command reader writer = do+ runPipe (writer <+< serializer <+< sendCommand)+ runPipe (receiveResponse+ <+< (deserializer >> return Nothing)+ <+< (reader >> return Nothing))+ where+ sendCommand = do+ yield command++ receiveResponse = do+ res <- await+ return (Just res)++-- | Wait for commands on the incoming pipe, handle them, and send the+-- reponses over the outgoing pipe.+commandReceiver :: (Serialize a, Serialize b) => (a -> IO b) -> Handler ()+commandReceiver executeCommand reader writer = do+ runPipe (writer <+< serializer+ <+< commandExecuter+ <+< deserializer <+< reader)+ where+ commandExecuter = forever $ do+ comm <- await+ yield =<< lift (executeCommand comm)
+ Control/Pipe/Serialize.hs view
@@ -0,0 +1,48 @@+-- | This module provides the 'deserializer' and 'serializer' pipes to+-- convert 'B.ByteString's off of pipes into typed values.+--+-- In order to use it, the types of the values need to have+-- 'Serialize' instances. These can be derived automatically using+-- "Ghc.Generics":+--+-- > {-# LANGUAGE DeriveGeneric #-}+-- >+-- > data Foo = Bar String | Baz Int+-- > deriving ( Generic )+-- >+-- > instance Serialize Foo+--+-- Note that in the above example: we use the @DeriveGeneric@+-- extension, derive a @Generic@ instance for our data-type, and write+-- an /empty/ @Serialize@ instance.+--+module Control.Pipe.Serialize (+ -- * Pipes+ serializer, deserializer+ ) where++import Data.ByteString.Char8 ( ByteString )+import Data.Serialize ( Serialize, get, encode+ , Result(..), runGetPartial )+import Control.Pipe ( Pipe, await, yield )+import Control.Monad ( forever )++-- | De-serialize data from strict 'ByteString's. Uses @cereal@'s+-- incremental 'Data.Serialize.Get' parser.+deserializer :: (Serialize a, Monad m) => Pipe ByteString a m ()+deserializer = loop Nothing Nothing+ where+ loop mk mbin = do+ bin <- maybe await return mbin+ case (maybe (runGetPartial get) id mk) bin of+ Fail reason -> fail reason+ Partial k -> loop (Just k) Nothing+ Done c bin' -> do+ yield c+ loop Nothing (Just bin')++-- | Serialize data into strict 'ByteString's.+serializer :: (Serialize a, Monad m) => Pipe a ByteString m ()+serializer = forever $ do+ x <- await+ yield (encode x)
+ Control/Pipe/Socket.hs view
@@ -0,0 +1,79 @@+{-# LANGUAGE ScopedTypeVariables #-}++-- Thank you:+-- <a href="https://github.com/pcapriotti/pipes-network">pipes-network</a>++module Control.Pipe.Socket (+ -- * Socket pipes+ socketReader, socketWriter,++ -- * Socket server/client+ Handler, runSocketServer, runSocketClient+ ) where++import Control.Concurrent ( forkIO )+import qualified Control.Exception as CE+import Control.Monad ( forever, unless )+import Control.Monad.IO.Class ( MonadIO(..) )+import Control.Monad.Trans.Class ( lift )+import Control.Pipe ( Consumer, Producer, await, yield )+import Data.ByteString.Char8 ( ByteString )+import qualified Data.ByteString.Char8 as B+import Network.Socket ( Socket )+import qualified Network.Socket as NS+import Network.Socket.ByteString ( sendAll, recv )++-- | Stream data from the socket.+socketReader :: (MonadIO m) => Socket -> Producer ByteString m ()+socketReader socket = do+ bin <- lift . liftIO $ recv socket 4096+ unless (B.null bin) $ do+ yield bin+ socketReader socket++-- | Stream data to the socket.+socketWriter :: (MonadIO m) => Socket -> Consumer ByteString m ()+socketWriter socket = forever $ do+ bin <- await+ lift . liftIO $ sendAll socket bin++-- | A simple handler: takes an incoming stream of 'ByteString's, an+-- stream of 'ByteString's, and ties them together somehow.+-- Conceptually, the simplest handler would be @identity@:+--+-- > import Control.Monad+-- > import Control.Pipe+-- > import Data.ByteString.Char8+-- >+-- > handler reader writer = do+-- > let identity = forever $ do+-- > x <- await+-- > yield x+-- > runPipe (writer <+< identity <+< reader)+--+-- See the @pipes@ tutorial for more examples of writing pipes.+--+-- Since 'ByteString's are fairly boring by themseleves, have a look+-- at "Control.Pipe.Serialize" which lets you deserialize/serialize+-- pipes of 'ByteString's easily.+type Handler r = Producer ByteString IO ()+ -> Consumer ByteString IO ()+ -> IO r++-- | Listen for connections on the given socket, and run 'Handler' on+-- each received connection. The socket should previously have been+-- bound to a port or to a file. Each handler is run in its own+-- thread. Even in case of an error, the handlers' sockets are+-- closed.+runSocketServer :: (MonadIO m) => Socket -> Handler () -> m ()+runSocketServer lsocket handler = liftIO $ forever $ do+ (socket, _addr) <- NS.accept lsocket+ _ <- forkIO $ CE.finally+ (handler (socketReader socket) (socketWriter socket))+ (NS.sClose socket)+ return ()++-- | Run 'Handler' on the given socket.+runSocketClient :: (MonadIO m) => Socket -> Handler r -> m r+runSocketClient socket handler = liftIO $ do+ handler (socketReader socket) (socketWriter socket)
+ LICENSE view
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Interpretation of Sections 15 and 16.++ If the disclaimer of warranty and limitation of liability provided+above cannot be given local legal effect according to their terms,+reviewing courts shall apply local law that most closely approximates+an absolute waiver of all civil liability in connection with the+Program, unless a warranty or assumption of liability accompanies a+copy of the Program in return for a fee.++ END OF TERMS AND CONDITIONS++ How to Apply These Terms to Your New Programs++ If you develop a new program, and you want it to be of the greatest+possible use to the public, the best way to achieve this is to make it+free software which everyone can redistribute and change under these terms.++ To do so, attach the following notices to the program. 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If not, see <http://www.gnu.org/licenses/>.++Also add information on how to contact you by electronic and paper mail.++ If the program does terminal interaction, make it output a short+notice like this when it starts in an interactive mode:++ <program> Copyright (C) <year> <name of author>+ This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.+ This is free software, and you are welcome to redistribute it+ under certain conditions; type `show c' for details.++The hypothetical commands `show w' and `show c' should show the appropriate+parts of the General Public License. Of course, your program's commands+might be different; for a GUI interface, you would use an "about box".++ You should also get your employer (if you work as a programmer) or school,+if any, to sign a "copyright disclaimer" for the program, if necessary.+For more information on this, and how to apply and follow the GNU GPL, see+<http://www.gnu.org/licenses/>.++ The GNU General Public License does not permit incorporating your program+into proprietary programs. If your program is a subroutine library, you+may consider it more useful to permit linking proprietary applications with+the library. If this is what you want to do, use the GNU Lesser General+Public License instead of this License. But first, please read+<http://www.gnu.org/philosophy/why-not-lgpl.html>.+
+ Makefile view
@@ -0,0 +1,25 @@+.PHONY: all build dist install test clean doc++all: build test++build: dist/setup-config+ grep -E "$ " Memo.md | sed 's/$ //' > Memo.hs+ cabal build++dist: test+ cabal sdist++install: build+ cabal install++test: build+ cabal test++clean:+ cabal clean++dist/setup-config: daemons.cabal+ cabal configure --enable-tests++doc: build+ cabal haddock
+ Memo.hs view
@@ -0,0 +1,59 @@+{-# LANGUAGE DeriveGeneric, OverloadedStrings #-}++module Main where++import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar )+import Data.ByteString.Char8 ( ByteString )+import Data.Default ( def )+import Data.Serialize ( Serialize )+import Data.String ( fromString )+import qualified Data.Map as M+import GHC.Generics+import System.Environment ( getArgs )+import System.Daemon++data Command = Put ByteString ByteString+ | Get ByteString+ deriving ( Generic, Show )++instance Serialize Command++data Response = Failed String+ | Value ByteString+ deriving ( Generic, Show )++instance Serialize Response++type Book = M.Map ByteString ByteString++handleCommand :: MVar Book -> Command -> IO Response+handleCommand bookVar comm = modifyMVar bookVar $ \book -> return $+ case comm of+ Get key -> ( book+ , maybe (Failed "not found") Value (M.lookup key book) )+ Put key value -> ( M.insert key value book+ , Value "ok" )++main :: IO ()+main = do+ bookVar <- newMVar M.empty+ let options = def { daemonPort = 7856 }+ startDaemon "memo" options (handleCommand bookVar)+ args <- getArgs+ let args' = map fromString args+ res <- case args' of+ ["get", key] -> runClient "localhost" 7856 (Get key)+ ["put", key, value] -> runClient "localhost" 7856 (Put key value)+ _ -> error "invalid command"+ print (res :: Maybe Response)++{-+% dist/build/memo/memo get apples+Just (Failed "not found")++% dist/build/memo/memo put apples 23+Just (Value "ok")++% dist/build/memo/memo get apples+Just (Value "23")+-}
+ NEWS.md view
+ PMTQ.hs view
@@ -0,0 +1,98 @@+{-# LANGUAGE DeriveGeneric, OverloadedStrings #-}++module Main where++import Control.Concurrent.Chan ( Chan, newChan, readChan, writeChan )+import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar )+import Control.Monad ( forever )+import Control.Monad.Trans.Class ( lift )+import Control.Pipe ( runPipe, (<+<), await, yield )+import Control.Pipe.Serialize ( serializer, deserializer )+import Control.Pipe.Socket ( Handler )+import Data.ByteString.Char8 ( ByteString )+import qualified Data.ByteString.Char8 as B+import Data.Char ( toLower )+import Data.Default ( def )+import Data.Serialize ( Serialize )+import Data.String ( fromString )+import qualified Data.Map as M+import GHC.Generics+import Network.Socket ( withSocketsDo )+import System.Environment ( getArgs )+import System.Daemon+import System.IO ( hPutStrLn, stderr )++data Command = Push ByteString ByteString+ | Pop ByteString+ | Consume ByteString+ deriving ( Generic, Show )++instance Serialize Command++data Response = Value ByteString+ deriving ( Generic, Show )++instance Serialize Response++type Registry = M.Map ByteString (Chan ByteString)++handleCommands :: MVar Registry -> Handler ()+handleCommands registryVar reader writer = do+ runPipe (writer <+< serializer+ <+< commandExecuter+ <+< deserializer <+< reader)+ where+ commandExecuter = forever $ do+ comm <- await+ case comm of+ Pop topic -> do+ ch <- lift $ getCreateChan topic+ transferToPipeFromChan ch+ Consume topic -> do+ ch <- lift $ getCreateChan topic+ forever $ transferToPipeFromChan ch+ Push topic val -> do+ ch <- lift $ getCreateChan topic+ lift $ writeChan ch val+ yield (Value "ok")++ -- Transfer a value from the given channel to the pipe.+ transferToPipeFromChan ch = do+ val <- lift $ readChan ch+ yield (Value val)++ -- Get the channel for the given topic, and create it if it does+ -- not already exist.+ getCreateChan topic = modifyMVar registryVar $ \registry -> do+ case M.lookup topic registry of+ Nothing -> do+ ch <- newChan+ return (M.insert topic ch registry, ch)+ Just ch -> do+ return (registry, ch)++main :: IO ()+main = withSocketsDo $ do+ registryVar <- newMVar M.empty+ let options = def { daemonPort = 7857 }+ startDaemonWithHandler "pmtq" options (handleCommands registryVar)+ args <- getArgs+ let args' = map (fromString . map toLower) args+ case args' of+ ["pop", key] -> do+ res <- runClient "localhost" 7857 (Pop key)+ printResult res+ ["push", key, value] -> do+ res <- runClient "localhost" 7857 (Push key value)+ printResult res+ ["consume", key] -> do+ runClientWithHandler "localhost" 7857 $ \reader writer -> do+ runPipe (writer <+< serializer <+< yield (Consume key))+ runPipe ((forever $ await >>= \res -> lift (printResult (Just res)))+ <+< deserializer <+< reader)+ _ -> do+ error "invalid command"+ where+ printResult :: Maybe Response -> IO ()+ printResult Nothing = hPutStrLn stderr "no response"+ printResult (Just (Value val)) = B.putStrLn val
+ README.md view
@@ -0,0 +1,80 @@+daemons+=======++> Daemons in Haskell made fun and easy++Example+-------++Here's+[AddOne](https://github.com/scvalex/daemons/blob/master/AddOne.hs), a+simple daemon that waits for a number and responds with the+incremented number.++ import Data.Default ( def )+ import System.Environment ( getArgs )+ import System.Daemon++ addOne :: Int -> IO Int+ addOne n = return (n + 1)++ main :: IO ()+ main = do+ startDaemon "addOne" def addOne+ [n] <- getArgs+ res <- runClient "localhost" 5000 ((read n) :: Int)+ print (res :: Maybe Int)++Running it, we see:++ % addone 22+ Just 23+ % addone 41+ Just 42++The two important functions above are `startDaemon`, which checks if a+daemon named `addOne` is already running, and starts it if not, and+`runClient` which connects to the daemon running on `localhost:5000`,+passes it a number, and waits for the response.++For a less trivial example, see the in-memory key-value store,+[Memo](https://github.com/scvalex/daemons/blob/master/Memo.md).++For an example that uses the streaming interface of `daemons`, see+[PMTQ](https://github.com/scvalex/daemons/blob/master/PMTQ.hs) (Poor+Man's Task Queue).++Installation+------------++This package is on+[Hackage](http://hackage.haskell.org/package/daemons). To install+it, run:++ cabal update+ cabal install daemons++Modules+-------++ - `Control.Pipe.C3` provides simple RPC-like wrappers for pipes.++ - `Control.Pipe.Serialize` provides pipes to serialize and+ deserialize streams of strict `ByteString`s using+ [cereal](http://hackage.haskell.org/package/cereal).++ - `Control.Pipe.Socket` provides functions to setup strict+ `ByteString` pipes around sockets.++ - `System.Daemon` provides a high-level interface to starting+ daemonized programs that are controlled through sockets.++ - `System.Posix.Daemon` provides a low-level interface to starting,+ and controlling detached jobs.++See also+--------++ - `pipes` [The Pipes Tutorial](http://hackage.haskell.org/packages/archive/pipes/latest/doc/html/Control-Pipe-Tutorial.html)++ - `C3` [Wikipedia](https://en.wikipedia.org/wiki/Command,_control,_and_communications#Command.2C_control_and_communications)
+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain
+ System/Daemon.hs view
@@ -0,0 +1,156 @@+module System.Daemon (+ -- * Daemons+ startDaemon, startDaemonWithHandler,++ -- * Clients,+ runClient, runClientWithHandler,++ -- * Types+ DaemonOptions(..), PidFile(..), HostName, Port,++ -- * Helpers+ bindPort, getSocket+ ) where++import Control.Concurrent ( threadDelay )+import qualified Control.Exception as CE+import Control.Monad ( when )+import Control.Pipe.C3 ( commandSender, commandReceiver )+import Control.Pipe.Socket ( Handler, runSocketServer, runSocketClient )+import Data.Default ( Default(..) )+import Data.Serialize ( Serialize )+import Data.String ( IsString(..) )+import Network.Socket ( Socket, SockAddr(..), Family(..), SocketType(..)+ , SocketOption(..), setSocketOption+ , socket, sClose, connect, bindSocket, listen+ , getAddrInfo, addrAddress+ , defaultProtocol, iNADDR_ANY, maxListenQueue )+import System.Directory ( getHomeDirectory )+import System.FilePath ( (</>), (<.>) )+import System.Posix.Daemon ( runDetached, isRunning )++type Port = Int+type HostName = String++-- | The configuration options of a daemon. See 'startDaemon' for a+-- description of each.+data DaemonOptions = DaemonOptions+ { daemonPort :: Port+ , daemonPidFile :: PidFile+ } deriving ( Show )++instance Default DaemonOptions where+ def = DaemonOptions { daemonPort = 5000+ , daemonPidFile = InHome+ }++-- | The location of the daemon's pidfile.+data PidFile = InHome+ | PidFile FilePath+ deriving ( Show )++instance IsString PidFile where+ fromString = PidFile++-- | Simple wrapper around 'startDaemonWithHandler' which uses a+-- simple function to respond to commands and doesn't deal with pipes.+--+-- The @handler@ is just a function that takes a command and returns a+-- response.+startDaemon :: (Serialize a, Serialize b)+ => String -- ^ name+ -> DaemonOptions -- ^ options+ -> (a -> IO b) -- ^ handler+ -> IO ()+startDaemon name options executeCommand = do+ startDaemonWithHandler name options (commandReceiver executeCommand)++-- | Start a daemon running on the given port, using the given handler+-- to respond to events. If the daemon is already running, just+-- return.+--+-- The pidfile @PidFile options@ will be created and locked. This+-- function checks the pidfile to see if the daemon is already+-- running.+--+-- The daemon will listen for incoming connections on all interfaces+-- on @daemonPort options@.+--+-- The @handler@ is a function that takes the reader and writer+-- 'ByteString' pipes and does something with them. See+-- 'commandReceiver' for an example handler.+startDaemonWithHandler :: String -- ^ name+ -> DaemonOptions -- ^ options+ -> Handler () -- ^ handler+ -> IO ()+startDaemonWithHandler name options handler = do+ home <- getHomeDirectory+ let pidfile = case daemonPidFile options of+ InHome -> home </> ("." ++ name) <.> "pid"+ PidFile path -> path+ running <- isRunning pidfile+ when (not running) $ do+ runDetached (Just pidfile) def $ do+ CE.bracket+ (bindPort (daemonPort options))+ sClose+ (\lsocket ->+ runSocketServer lsocket handler)+ threadDelay 1000000++-- | Send a command to the daemon running at the given network address+-- and wait for a response.+--+-- This is a simple wrapper around 'runClientWithHandler' that sends a+-- single command and waits for a single response.+--+-- If the connection is closed before receiving a response, return+-- 'Nothing'.+runClient :: (Serialize a, Serialize b)+ => HostName -- ^ hostname+ -> Port -- ^ port+ -> a -- ^ command+ -> IO (Maybe b)+runClient hostname port comm =+ runClientWithHandler hostname port (commandSender comm)++-- | Connect to the given network address and run the handler on the+-- reader and wrier pipes for the socket.+--+-- The @handler@ is a function that takes the reader and writer+-- 'ByteString' pipes and does something with them. For an example+-- handler, see 'commandSender', which sends a command and waits for a+-- response.+runClientWithHandler :: HostName -- ^ hostname+ -> Port -- ^ port+ -> Handler a -- ^ command+ -> IO a+runClientWithHandler hostname port handler = do+ CE.bracket+ (getSocket hostname port)+ sClose+ (\s -> runSocketClient s handler)++-- | Create a socket and bind it to the given port.+bindPort :: Port -> IO Socket+bindPort port = do+ CE.bracketOnError+ (socket AF_INET Stream defaultProtocol)+ sClose+ (\s -> do+ setSocketOption s ReuseAddr 1+ bindSocket s (SockAddrInet (fromIntegral port)+ iNADDR_ANY)+ listen s maxListenQueue+ return s)++-- | Create a socket connected to the given network address.+getSocket :: HostName -> Port -> IO Socket+getSocket hostname port = do+ addrInfos <- getAddrInfo Nothing (Just hostname) (Just $ show port)+ CE.bracketOnError+ (socket AF_INET Stream defaultProtocol)+ sClose+ (\s -> do+ connect s (addrAddress $ head addrInfos)+ return s)
+ System/Posix/Daemon.hs view
@@ -0,0 +1,191 @@+-- | This module provides a simple interface to creating, checking the+-- status of, and stopping background jobs.+--+-- Use 'runDetached' to start a background job. For instance, here is+-- a daemon that peridically hits a webserver:+--+-- > import Control.Concurrent+-- > import Control.Monad+-- > import Data.Default+-- > import Data.Maybe+-- > import Network.BSD+-- > import Network.HTTP+-- > import Network.URI+-- > import System.Posix.Daemon+-- >+-- > main :: IO ()+-- > main = runDetached (Just "diydns.pid") def $ forever $ do+-- > hostname <- getHostName+-- > _ <- simpleHTTP+-- > (Request { rqURI = fromJust (parseURI "http://foo.com/dns")+-- > , rqMethod = GET+-- > , rqHeaders = []+-- > , rqBody = hostname })+-- > threadDelay (600 * 1000 * 1000)+--+-- To check if the above job is running, use 'isRunning' with the same+-- pidfile:+--+-- > isRunning "diydns.pid"+--+-- Finally, to stop the above job (maybe because we're rolling a new+-- version of it), use 'kill':+--+-- > kill "diydns.pid"+--+-- As a side note, the code above is a script that the author uses as+-- a sort of homebrew dynamic DNS: the remote address is a CGI script+-- that records the IP addresses of all incoming requests in separate+-- files named after the contents of the requests; the addresses are+-- then viewable with any browser.+module System.Posix.Daemon (+ -- * Starting+ runDetached, Redirection(..),++ -- * Status+ isRunning,++ -- * Stopping+ kill, brutalKill+ ) where++import Prelude hiding ( FilePath )++import Control.Monad ( when )+import Data.Default ( Default(..) )+import System.Directory ( doesFileExist )+import System.FilePath ( FilePath )+import System.IO ( SeekMode(..), hFlush, stdout )+import System.Posix.Files ( stdFileMode )+import System.Posix.IO ( openFd, OpenMode(..), defaultFileFlags, closeFd+ , dupTo, stdInput, stdOutput, stdError, getLock+ , createFile+ , LockRequest (..), setLock, fdWrite, fdRead )+import System.Posix.Process ( getProcessID, forkProcess, createSession )+import System.Posix.Signals ( Signal, signalProcess, sigQUIT, sigKILL )++-- | Where should the output (and input) of a daemon be redirected to?+-- (we can't just leave it to the current terminal, because it may be+-- closed, and that would kill the daemon).+--+-- When in doubt, just use 'def', the default value.+--+-- 'DevNull' causes the output to be redirected to @\/dev\/null@. This+-- is safe and is what you want in most cases.+--+-- If you don't want to lose the output (maybe because you're using it+-- for logging), use 'ToFile', instead.+data Redirection = DevNull+ | ToFile FilePath+ deriving ( Show )++instance Default Redirection where+ def = DevNull++-- | Run the given action detached from the current terminal; this+-- creates an entirely new process. This function returns+-- immediately. Uses the double-fork technique to create a well+-- behaved daemon. If @pidfile@ is given, check/write it; if we+-- cannot obtain a lock on the file, another process is already using+-- it, so fail. The @redirection@ parameter controls what to do with+-- the standard channels (@stdin@, @stderr@, and @stdout@).+--+-- See: <http://www.enderunix.org/docs/eng/daemon.php>+--+-- Note: All unnecessary fds should be close before calling this.+-- Otherwise, you get an fd leak.+runDetached :: Maybe FilePath -- ^ pidfile+ -> Redirection -- ^ redirection+ -> IO () -- ^ program+ -> IO ()+runDetached maybePidFile redirection program = do+ -- check if the pidfile exists; fail if it does+ checkPidFile+ -- fork first child+ ignore $ forkProcess $ do+ -- create a new session and make this process its leader; see+ -- setsid(2)+ ignore $ createSession+ -- fork second child+ ignore $ forkProcess $ do+ -- create the pidfile+ writePidFile+ -- remap standard fds+ remapFds+ -- run the daemon+ program+ where+ ignore act = act >> return ()++ -- Remap the standard channels based on the @redirection@+ -- parameter.+ remapFds = do+ devnull <- openFd "/dev/null" ReadOnly Nothing defaultFileFlags+ ignore (dupTo devnull stdInput)+ closeFd devnull++ let file = case redirection of+ DevNull -> "/dev/null"+ ToFile filepath -> filepath+ fd <- openFd file ReadWrite (Just stdFileMode) defaultFileFlags+ hFlush stdout+ mapM_ (dupTo fd) [stdOutput, stdError]+ closeFd fd++ -- Convert the 'FilePath' @pidfile@ to a regular 'String' and run+ -- the action with it.+ withPidFile act =+ case maybePidFile of+ Nothing -> return ()+ Just pidFile -> act pidFile++ -- Check if the pidfile exists; fail if it does, and create it, otherwise+ checkPidFile = withPidFile $ \pidFile -> do+ running <- isRunning pidFile+ when running $ fail "already running"++ writePidFile = withPidFile $ \pidFile -> do+ fd <- createFile pidFile stdFileMode+ setLock fd (WriteLock, AbsoluteSeek, 0, 0)+ pid <- getProcessID+ ignore $ fdWrite fd (show pid)+ -- note that we do not close the fd; doing so would release+ -- the lock++-- | Return 'True' if the given file is locked by a process. In our+-- case, returns 'True' when the daemon that created the file is still+-- alive.+isRunning :: FilePath -> IO Bool+isRunning pidFile = do+ dfe <- doesFileExist pidFile+ if dfe+ then do+ fd <- openFd pidFile ReadWrite Nothing defaultFileFlags+ -- is there an *incompatible* lock on the pidfile?+ ml <- getLock fd (WriteLock, AbsoluteSeek, 0, 0)+ (pid, _) <- fdRead fd 100+ closeFd fd+ case ml of+ Nothing -> do+ pid' <- getProcessID+ return (read pid == pid')+ Just _ -> do+ return True+ else do+ return False++-- | Send 'sigQUIT' to the process recorded in the pidfile. This+-- gives the process a chance to close cleanly.+kill :: FilePath -> IO ()+kill = signalProcessByFilePath sigQUIT++-- | Send 'sigKILL' to the process recorded in the pidfile. This+-- immediately kills the process.+brutalKill :: FilePath -> IO ()+brutalKill = signalProcessByFilePath sigKILL++-- | Send a signal to a process whose pid is recorded in a file.+signalProcessByFilePath :: Signal -> FilePath -> IO ()+signalProcessByFilePath signal pidFile = do+ pid <- readFile pidFile+ signalProcess signal (read pid)
+ Test/Daemon.hs view
@@ -0,0 +1,122 @@+{-# LANGUAGE OverloadedStrings, ScopedTypeVariables #-}++module Main where++import Control.Concurrent+import Control.Exception+import Control.Monad+import Data.Default+import Data.Monoid+import System.Directory+import System.Posix.Daemon+import System.Posix.Process++import Test.Framework+import Test.Framework.Providers.HUnit+import Test.HUnit++main :: IO ()+main = defaultMainWithOpts+ [ testCase "firstRun" testFirst+ , testCase "withPid" testWithPid+ , testCase "isRunning" testIsRunning+ , testCase "exclusion" testExclusion+ , testCase "release" testRelease+ , testCase "redirection" testRedirection+ ] mempty++ensureRemoved :: [FilePath] -> IO ()+ensureRemoved filepaths = forM_ filepaths $ \filepath -> do+ exists <- doesFileExist filepath+ when exists $ do+ removeFile filepath++-- Wait the given number of ms.+sleep :: Int -> IO ()+sleep n = threadDelay (n * 1000)++testFirst :: Assertion+testFirst = flip finally (ensureRemoved ["tmp"]) $ do+ let txtExp = "42"+ runDetached Nothing def $ do+ writeFile "tmp" txtExp+ sleep 500+ txt <- readFile "tmp"+ txt @?= txtExp++testWithPid :: Assertion+testWithPid = flip finally (ensureRemoved ["pid", "tmp"]) $ do+ let txtExp = "42"+ runDetached (Just "pid") def $ do+ pid <- getProcessID+ pid' <- readFile "pid"+ if show pid == pid'+ then writeFile "tmp" txtExp+ else writeFile "tmp" "wrong pid recorded"+ sleep 500+ txt <- readFile "tmp"+ txt @?= txtExp+ pid <- readFile "pid"+ null pid @?= False++testIsRunning :: Assertion+testIsRunning = flip finally (ensureRemoved ["pid", "tmp"]) $ do+ runDetached (Just "pid") def $ do+ running <- isRunning "pid"+ writeFile "tmp" (show running)+ sleep 10000+ sleep 500++-- FIXME There's some weird behaviour when the process that has locked+-- the file (or its ancestors, or its descendents) use 'isRunning'.+--+-- The semantics of 'fnctl' are "try to aquire the requested lock; if+-- there is an incompatible lock in place, return it". Of course,+-- this means that the process that acquired the lock sees it as+-- unlocked.+--+-- We mitigated the obvious part of the problem (same process) by+-- checking the pid in the pidfile. Now, we're left with the case+-- where an ancestor of the process thinks it can set the lock.++ -- running <- isRunning "pid"+ -- running @?= True+ txt <- readFile "tmp"+ txt @?= "True"++testExclusion :: Assertion+testExclusion = flip finally (ensureRemoved ["pid", "tmp"]) $ do+ let txtExp = "ok"+ runDetached (Just "pid") def $ do+ sleep 1000+ sleep 500+ handle (\(_ :: SomeException) -> writeFile "tmp" txtExp)+ (runDetached (Just "pid") def $ do+ writeFile "tmp" "failed")+ sleep 500+ txt <- readFile "tmp"+ txt @?= txtExp++testRelease :: Assertion+testRelease = flip finally (ensureRemoved ["pid", "tmp"]) $ do+ let txtExp = "ok"+ runDetached (Just "pid") def $ do+ writeFile "tmp" txtExp+ sleep 500+ txt <- readFile "tmp"+ txt @?= txtExp+ let txtExp' = "ok"+ runDetached (Just "pid") def $ do+ writeFile "tmp" txtExp'+ sleep 500+ txt' <- readFile "tmp"+ txt' @?= txtExp'++testRedirection :: Assertion+testRedirection = flip finally (ensureRemoved ["tmp"]) $ do+ let txtExp = "ok"+ runDetached Nothing (ToFile "tmp") $ do+ putStr "ok"+ sleep 500+ txt <- readFile "tmp"+ txt @?= txtExp
+ daemons.cabal view
@@ -0,0 +1,80 @@+Name: daemons+Version: 0.1.0+Cabal-Version: >= 1.8+License: GPL-3+License-File: LICENSE+Stability: experimental+Author: Alexandru Scvortov <scvalex@gmail.com>+Maintainer: scvalex@gmail.com+Homepage: https://github.com/scvalex/daemons+Category: Text+Synopsis: Daemons in Haskell made fun and easy+Build-Type: Simple+Description:+ "Control.Pipe.C3" provides simple RPC-like wrappers for pipes.+ .+ "Control.Pipe.Serialize" provides serialization and+ incremental deserialization pipes.+ .+ "Control.Pipe.Socket" provides functions to setup pipes around+ sockets.+ .+ "System.Daemon" provides a high-level interface to starting+ daemonized programs that are controlled through sockets.+ .+ "System.Posix.Daemon" provides a low-level interface to+ starting, and controlling detached jobs.+ .+ See the @README.md@ file and the homepage for details.++Extra-Source-Files: Makefile++Data-Files: README.md, NEWS.md, LICENSE++Source-repository head+ Type: git+ Location: git://github.com/scvalex/daemons.git++Library+ Build-depends: base >= 4 && < 5, bytestring, cereal,+ data-default, directory, filepath, network, pipes,+ transformers, unix+ Ghc-options: -Wall -threaded+ Exposed-modules: Control.Pipe.C3,+ Control.Pipe.Serialize,+ Control.Pipe.Socket,+ System.Daemon,+ System.Posix.Daemon+ Other-modules:++Executable memo+ Build-depends: base >= 4 && < 5, bytestring, cereal,+ containers, data-default, directory, filepath,+ ghc-prim, pipes, transformers, network, unix+ Main-Is: Memo.hs+ Ghc-options: -Wall++Executable addone+ Build-depends: base >= 4 && < 5, bytestring, cereal,+ containers, data-default, directory, filepath,+ ghc-prim, pipes, transformers, network, unix+ Main-Is: AddOne.hs+ Ghc-options: -Wall++Executable queue+ Build-depends: base >= 4 && < 5, bytestring, cereal,+ containers, data-default, directory, filepath,+ ghc-prim, pipes, transformers, network, unix+ Main-Is: PMTQ.hs+ Ghc-options: -Wall++Test-suite daemon+ Hs-Source-Dirs: Test, .+ Main-Is: Daemon.hs+ Type: exitcode-stdio-1.0++ Build-Depends: base >= 4 && < 5, data-default, directory,+ filepath, unix+ Ghc-Options: -Wall++ Build-Depends: test-framework, test-framework-hunit, HUnit