├── .envrc ├── .gitignore ├── .travis.yml ├── LICENSE ├── Makefile ├── NEWS.md ├── README.md ├── TODO.org ├── daemons.cabal ├── examples ├── AddOne.hs ├── Memo.hs ├── Memo.md ├── Name.hs └── Queue.hs ├── flake.lock ├── flake.nix ├── src ├── Control │ └── Pipe │ │ ├── C3.hs │ │ ├── Serialize.hs │ │ └── Socket.hs └── System │ ├── Daemon.hs │ └── Posix │ └── Daemon.hs ├── stack.yaml ├── stack.yaml.lock └── test └── Daemon.hs /.envrc: -------------------------------------------------------------------------------- 1 | use flake 2 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | dist/ 2 | dist-newstyle/ 3 | cabal-dev/ 4 | .direnv/ 5 | cabal.project.local 6 | cabal.project.local~ 7 | .stack-work/ 8 | Setup.hs 9 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: haskell 2 | ghc: 3 | - "8.4" 4 | - "8.6" 5 | - "8.8" 6 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | 676 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | CABAL := $(shell cabal-dev --version > /dev/null && echo cabal-dev || echo cabal) 2 | 3 | all: build test 4 | 5 | .PHONY: all build dist install clean doc p test ghci 6 | 7 | build: dist/setup-config 8 | grep -E "$ " examples/Memo.md | sed 's/$ //' > examples/Memo.hs 9 | $(CABAL) build 10 | 11 | dist: build 12 | cabal sdist 13 | 14 | install: build 15 | cabal install 16 | 17 | test: build 18 | $(CABAL) test 19 | 20 | clean: 21 | $(CABAL) clean 22 | rm -rf cabal-dev/ 23 | 24 | dist/setup-config: daemons.cabal 25 | # If you don't have all the necessary packages installed on the first 26 | # run, run `cabal-dev install`. 27 | $(CABAL) configure --enable-tests || $(CABAL) install --enable-tests 28 | 29 | doc: build 30 | $(CABAL) haddock 31 | 32 | p: 33 | permamake.sh $(shell find src/ -name '*.hs') \ 34 | $(shell find test/ -name '*.hs') \ 35 | *.cabal \ 36 | Makefile 37 | 38 | ghci: build 39 | cabal-dev ghci 40 | -------------------------------------------------------------------------------- /NEWS.md: -------------------------------------------------------------------------------- 1 | Changes 2 | ======= 3 | 4 | 0.4.0 (29 Sep 2023) 5 | ------------------- 6 | 7 | - update to work with ghc-9.6; thank you, @tfausak 8 | - bump min base version to 4.18 9 | 10 | 0.3.0 (03 Feb 2020) 11 | ------------------- 12 | 13 | - update to work with the new network library; thank you, @guibou 14 | 15 | 0.2.1 (03 Oct 2013) 16 | ------------------- 17 | 18 | - update to work with cereal-0.4.0; thank you, Henry Laxen 19 | 20 | 0.2.0 (15 Sep 2013) 21 | ------------------- 22 | 23 | - update to work with pipes-4.0.0; thank you, @gabriel439 24 | 25 | 0.1.2 (05 Apr 2013) 26 | ------------------- 27 | 28 | - add `System.Posix.Daemon.killAndWait`; thank you, @isturdy 29 | 30 | 0.1.1 (18 Aug 2012) 31 | ------------------- 32 | 33 | - do *not* use the `-threaded` runtime; 34 | 35 | - use of IPv4 to workaround unpredictable behaviours in different 36 | distros. 37 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | daemons 2 | ======= 3 | 4 | > Daemons in Haskell made fun and easy 5 | 6 | Example 7 | ------- 8 | 9 | Here's 10 | [AddOne](https://github.com/scvalex/daemons/blob/master/AddOne.hs), a 11 | simple daemon that waits for a number and responds with the 12 | incremented number. 13 | 14 | import Data.Default ( def ) 15 | import System.Environment ( getArgs ) 16 | import System.Daemon 17 | 18 | addOne :: Int -> IO Int 19 | addOne n = return (n + 1) 20 | 21 | main :: IO () 22 | main = do 23 | ensureDaemonRunning "addOne" def addOne 24 | [n] <- getArgs 25 | res <- runClient "localhost" 5000 ((read n) :: Int) 26 | print (res :: Maybe Int) 27 | 28 | Running it, we see: 29 | 30 | % addone 22 31 | Daemon started on port 5000 32 | Just 23 33 | % addone 41 34 | Just 42 35 | 36 | The two important functions above are `ensureDaemonRunning`, which 37 | checks if a daemon named `addOne` is already running, and starts it if 38 | not, and `runClient` which connects to the daemon running on 39 | `localhost:5000`, passes it a number, and waits for the response. 40 | 41 | What would I use this for? 42 | -------------------------- 43 | 44 | - You can use the `runDetached` from `System.Posix.Daemon` to turn 45 | your program into a daemon for Unix-like systems. You'd want to do 46 | this for practically every program that's meant to run as a server. 47 | 48 | - You can use the functions from `Control.Pipe.C3`, `Socket`, and 49 | `Serialize` to communicate with running Haskell program. At the 50 | simplest, you could query the program for its status, or instruct 51 | it to shutdown cleanly. A more complex use would be adding a full 52 | REPL into a running Haskell process (think `erl -remsh`). 53 | 54 | - You can use the helpers from `System.Daemon` to trivially do the 55 | above. Check out the following tutorials and examples for details. 56 | 57 | Tutorials and examples 58 | ---------------------- 59 | 60 | - [Memo](https://github.com/scvalex/daemons/blob/master/examples/Memo.md) - 61 | in which we write an in-memory key-value store, 62 | 63 | - [Queue](https://github.com/scvalex/daemons/blob/master/examples/Queue.hs) 64 | - a task queue using the streaming interface of `daemons`. 65 | 66 | Installation 67 | ------------ 68 | 69 | This package is on 70 | [Hackage](http://hackage.haskell.org/package/daemons). To install 71 | it, run: 72 | 73 | cabal update 74 | cabal install daemons 75 | 76 | Modules 77 | ------- 78 | 79 | - `Control.Pipe.C3` provides simple RPC-like wrappers for pipes. 80 | 81 | - `Control.Pipe.Serialize` provides pipes to serialize and 82 | deserialize streams of strict `ByteString`s using 83 | [cereal](http://hackage.haskell.org/package/cereal). 84 | 85 | - `Control.Pipe.Socket` provides functions to setup strict 86 | `ByteString` pipes around sockets. 87 | 88 | - `System.Daemon` provides a high-level interface to starting 89 | daemonized programs that are controlled through sockets. 90 | 91 | - `System.Posix.Daemon` provides a low-level interface to starting, 92 | and controlling detached jobs. 93 | 94 | See also 95 | -------- 96 | 97 | - `pipes` [The Pipes Tutorial](http://hackage.haskell.org/packages/archive/pipes/3.2.0/doc/html/Control-Proxy-Tutorial.html) 98 | 99 | - `C3` [Wikipedia](https://en.wikipedia.org/wiki/Command,_control,_and_communications#Command.2C_control_and_communications) 100 | -------------------------------------------------------------------------------- /TODO.org: -------------------------------------------------------------------------------- 1 | * TODO Update code to use new `Control.Proxy` namespace 2 | * TODO Get rid of IPv4-only hack when creating sockets 3 | -------------------------------------------------------------------------------- /daemons.cabal: -------------------------------------------------------------------------------- 1 | Name: daemons 2 | Version: 0.4.0 3 | Cabal-Version: 1.24 4 | License: GPL-3 5 | License-File: LICENSE 6 | Stability: experimental 7 | Author: Alexandru Scvortov 8 | Maintainer: scvalex@gmail.com 9 | Homepage: https://github.com/scvalex/daemons 10 | Category: System, Control, Network 11 | Synopsis: Daemons in Haskell made fun and easy 12 | Build-Type: Simple 13 | Description: 14 | "Control.Pipe.C3" provides simple RPC-like wrappers for pipes. 15 | . 16 | "Control.Pipe.Serialize" provides serialization and 17 | incremental deserialization pipes. 18 | . 19 | "Control.Pipe.Socket" provides functions to setup pipes around 20 | sockets. 21 | . 22 | "System.Daemon" provides a high-level interface to starting 23 | daemonized programs that are controlled through sockets. 24 | . 25 | "System.Posix.Daemon" provides a low-level interface to 26 | starting, and controlling detached jobs. 27 | . 28 | See the @README.md@ file and the homepage for details. 29 | 30 | Extra-Source-Files: Makefile 31 | 32 | Data-Files: README.md, NEWS.md, LICENSE, examples/Memo.md 33 | 34 | Source-repository head 35 | Type: git 36 | Location: git://github.com/scvalex/daemons.git 37 | 38 | Library 39 | Hs-Source-Dirs: src 40 | Build-depends: base >= 4.18 && < 5, 41 | bytestring >= 0.11 && < 0.12, 42 | cereal >= 0.4 && < 0.6, 43 | data-default >= 0.7 && < 0.8, 44 | directory >= 1.3 && < 1.4, 45 | filepath >= 1.4 && < 1.5, 46 | ghc-prim >= 0.10 && < 0.11, 47 | network >= 3.1 && < 3.2, 48 | pipes >= 4.0 && < 4.4, 49 | transformers >= 0.6 && < 0.7, 50 | unix >= 2.8 && < 2.9 51 | Ghc-options: -Wall 52 | Exposed-modules: Control.Pipe.C3, 53 | Control.Pipe.Serialize, 54 | Control.Pipe.Socket, 55 | System.Daemon, 56 | System.Posix.Daemon 57 | Other-modules: 58 | Default-language: Haskell2010 59 | 60 | Executable memo 61 | Build-depends: base >= 4.18 && < 5, 62 | bytestring >= 0.11 && < 0.12, 63 | cereal >= 0.4 && < 0.6, 64 | containers >= 0.6 && < 0.7, 65 | daemons, 66 | data-default >= 0.7 && < 0.8, 67 | ghc-prim >= 0.10.0 && < 0.11 68 | Main-Is: examples/Memo.hs 69 | Ghc-options: -Wall 70 | Default-language: Haskell2010 71 | 72 | Executable addone 73 | Build-depends: base >= 4.18 && < 5, daemons, 74 | data-default >= 0.7 && < 0.8, 75 | ghc-prim >= 0.10 && < 0.11 76 | Main-Is: examples/AddOne.hs 77 | Ghc-options: -Wall 78 | Default-language: Haskell2010 79 | 80 | Executable queue 81 | Build-depends: base >= 4.18 && < 5, 82 | bytestring >= 0.11 && < 0.12, 83 | cereal >= 0.4 && < 0.6, 84 | containers >= 0.6 && < 0.7, 85 | daemons, 86 | data-default >= 0.7 && < 0.8, 87 | ghc-prim >= 0.10 && < 0.11, 88 | network >= 3.1 && < 3.2, 89 | pipes >= 4.0 && < 4.4, 90 | transformers >= 0.6 && < 0.7 91 | Main-Is: examples/Queue.hs 92 | Ghc-options: -Wall 93 | Default-language: Haskell2010 94 | 95 | Executable name 96 | Build-depends: base >= 4.18 && < 5, 97 | bytestring >= 0.11 && < 0.12, 98 | cereal >= 0.4 && < 0.6, 99 | containers >= 0.6 && < 0.7, 100 | daemons, 101 | data-default >= 0.7 && < 0.8, 102 | ghc-prim >= 0.10.0 && < 0.11 103 | Main-Is: examples/Name.hs 104 | Ghc-options: -Wall 105 | Default-language: Haskell2010 106 | 107 | Test-suite daemon 108 | Hs-Source-Dirs: test 109 | Main-Is: Daemon.hs 110 | Type: exitcode-stdio-1.0 111 | Build-Depends: base >= 4.18 && < 5, daemons, 112 | data-default >= 0.7 && < 0.8, 113 | directory >= 1.3 && < 1.4, 114 | ghc-prim >= 0.10 && < 0.11, 115 | HUnit, test-framework, test-framework-hunit, 116 | unix >= 2.8 && < 2.9 117 | Ghc-Options: -Wall 118 | Default-language: Haskell2010 119 | -------------------------------------------------------------------------------- /examples/AddOne.hs: -------------------------------------------------------------------------------- 1 | module Main where 2 | 3 | import Data.Default ( def ) 4 | import System.Environment ( getArgs ) 5 | import System.Daemon 6 | 7 | addOne :: Int -> IO Int 8 | addOne n = return (n + 1) 9 | 10 | main :: IO () 11 | main = do 12 | ensureDaemonRunning "addOne" def addOne 13 | [n] <- getArgs 14 | res <- runClient "localhost" 5000 ((read n) :: Int) 15 | print (res :: Maybe Int) 16 | -------------------------------------------------------------------------------- /examples/Memo.hs: -------------------------------------------------------------------------------- 1 | {-# LANGUAGE DeriveGeneric, OverloadedStrings #-} 2 | 3 | module Main where 4 | 5 | import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar ) 6 | import Data.ByteString.Char8 ( ByteString ) 7 | import Data.Default ( def ) 8 | import Data.Serialize ( Serialize ) 9 | import Data.String ( fromString ) 10 | import qualified Data.Map as M 11 | import GHC.Generics 12 | import System.Environment ( getArgs ) 13 | import System.Daemon 14 | 15 | data Command = Put ByteString ByteString 16 | | Get ByteString 17 | deriving ( Generic, Show ) 18 | 19 | instance Serialize Command 20 | 21 | data Response = Failed String 22 | | Value ByteString 23 | deriving ( Generic, Show ) 24 | 25 | instance Serialize Response 26 | 27 | type Book = M.Map ByteString ByteString 28 | 29 | handleCommand :: MVar Book -> Command -> IO Response 30 | handleCommand bookVar comm = modifyMVar bookVar $ \book -> return $ 31 | case comm of 32 | Get key -> ( book 33 | , maybe (Failed "not found") Value (M.lookup key book) ) 34 | Put key value -> ( M.insert key value book 35 | , Value "ok" ) 36 | 37 | main :: IO () 38 | main = do 39 | bookVar <- newMVar M.empty 40 | let options = def { daemonPort = 7856 } 41 | ensureDaemonRunning "memo" options (handleCommand bookVar) 42 | args <- getArgs 43 | let args' = map fromString args 44 | res <- case args' of 45 | ["get", key] -> runClient "localhost" 7856 (Get key) 46 | ["put", key, value] -> runClient "localhost" 7856 (Put key value) 47 | _ -> error "invalid command" 48 | print (res :: Maybe Response) 49 | 50 | {- 51 | % dist/build/memo/memo get apples 52 | Daemon started on port 7856 53 | Just (Failed "not found") 54 | 55 | % dist/build/memo/memo put apples 23 56 | Just (Value "ok") 57 | 58 | % dist/build/memo/memo get apples 59 | Just (Value "23") 60 | -} 61 | -------------------------------------------------------------------------------- /examples/Memo.md: -------------------------------------------------------------------------------- 1 | Memo 2 | ==== 3 | 4 | > A simple in-memory key-value store 5 | 6 | Welcome to the first `daemons` tutorial, in which we walk through 7 | writing an in-memory key-value store with an RPC-like interface. The 8 | code for this tutorial is 9 | [Memo.hs](https://github.com/scvalex/daemons/blob/master/examples/Memo.hs). 10 | 11 | Concretely, we want a program such that: 12 | 13 | - `memo put x 42` associates the value `42` with the key `x`, and 14 | 15 | - `memo get x` returns the value `42`. 16 | 17 | First of all, the extensions and imports: 18 | 19 | {-# LANGUAGE DeriveGeneric, OverloadedStrings #-} 20 | 21 | 22 | We need `DeriveGenerics` for 23 | [cereal](http://hackage.haskell.org/package/cereal) to generate 24 | serializers and deserializers automatically, and we enable 25 | `OverloadedStrings` because it makes working with `ByteString`s much 26 | nicer. 27 | 28 | module Main where 29 | 30 | import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar ) 31 | import Data.ByteString.Char8 ( ByteString ) 32 | import Data.Default ( def ) 33 | import Data.Serialize ( Serialize ) 34 | import Data.String ( fromString ) 35 | import qualified Data.Map as M 36 | import GHC.Generics 37 | import System.Environment ( getArgs ) 38 | import System.Daemon 39 | 40 | 41 | Our key-value store will be a `Map ByteString ByteString` and we'll 42 | store it in an `MVar` to synchronize concurrent accesses. Instead of 43 | handcrafting a binary protocol for our daemon, we take the easy road 44 | and generate it automatically with `Data.Serialize` and 45 | [GHC.Generics](http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/generic-programming.html). 46 | 47 | We import `System.Daemon` which is the high-level interface to the 48 | `daemons` library. The daemons' configuration is an instance of 49 | [Data.Default](http://hackage.haskell.org/package/data-default), so 50 | we'll be able to use the defaults. 51 | 52 | data Command = Put ByteString ByteString 53 | | Get ByteString 54 | deriving ( Generic, Show ) 55 | 56 | instance Serialize Command 57 | 58 | 59 | We define a datatype for the `put ` and `get ` 60 | commands. We let GHC derive the `Generics` instance, which gives us a 61 | pure Haskell representation of the type; this is used by the 62 | `Serialize` instance to generate all the necessary binary 63 | serialization and deserialization code. 64 | 65 | data Response = Failed String 66 | | Value ByteString 67 | deriving ( Generic, Show ) 68 | 69 | instance Serialize Response 70 | 71 | 72 | Similarly, we define a datatype for the possible responses. These can 73 | either be values requested by `get `, or failure messages. 74 | 75 | type Book = M.Map ByteString ByteString 76 | 77 | handleCommand :: MVar Book -> Command -> IO Response 78 | handleCommand bookVar comm = modifyMVar bookVar $ \book -> return $ 79 | 80 | Our "book" is just a map of `ByteString`s; our command handler takes 81 | this map and a command, and returns a response. 82 | 83 | Whenever the daemon receives a command, it spawns a new thread and 84 | runs the command handler. We want to share the book between these 85 | concurrent calls to the handler, so we stick it in an 86 | [MVar](http://www.haskell.org/ghc/docs/7.4.2/html/libraries/base/Control-Concurrent-MVar.html). 87 | 88 | An `MVar` is basically a thread-safe box which holds at most *one* 89 | item. We use `modifyMVar` which takes the book out of the `MVar`, 90 | runs our function with it, and puts the returned book back in the 91 | `MVar`. 92 | 93 | case comm of 94 | Get key -> ( book 95 | , maybe (Failed "not found") Value (M.lookup key book) ) 96 | 97 | A `get ` command does not change the book, so we just return it. 98 | We look up the key and return its value or a failure message. 99 | 100 | Put key value -> ( M.insert key value book 101 | , Value "ok" ) 102 | 103 | 104 | A `put ` command inserts the key-value pair into the 105 | book, and returns a confirmation message. 106 | 107 | main :: IO () 108 | main = do 109 | bookVar <- newMVar M.empty 110 | let options = def { daemonPort = 7856 } 111 | ensureDaemonRunning "memo" options (handleCommand bookVar) 112 | 113 | Before doing anything else, we need to ensure that the daemon is 114 | running: we create an empty book, customize the daemon's default 115 | options, and finally start it. Note that `ensureDaemonRunning` checks 116 | if the daemon is running and starts it otherwise; so, the daemon will 117 | be started the first time the program is run, and all later runs will 118 | use the initial daemon. 119 | 120 | args <- getArgs 121 | let args' = map fromString args 122 | 123 | Now it's time to handle the user input. First, we convert all the 124 | arguments to `ByteString`s for ease of use. 125 | 126 | res <- case args' of 127 | ["get", key] -> runClient "localhost" 7856 (Get key) 128 | ["put", key, value] -> runClient "localhost" 7856 (Put key value) 129 | _ -> error "invalid command" 130 | 131 | Next, we parse the arguments into a command and send it to the daemon. 132 | We call `runClient` with the port we gave earlier to 133 | `ensureDaemonRunning` and with the parsed command. 134 | 135 | print (res :: Maybe Response) 136 | 137 | 138 | Finally, we print the returned response. Note that `runClient` is 139 | polymorphic in its return so we *need* to specify the type of the 140 | response. 141 | 142 | Now let's see it in action: 143 | 144 | {- 145 | % dist/build/memo/memo get apples 146 | Daemon started on port 7856 147 | Just (Failed "not found") 148 | 149 | % dist/build/memo/memo put apples 23 150 | Just (Value "ok") 151 | 152 | % dist/build/memo/memo get apples 153 | Just (Value "23") 154 | -} 155 | 156 | To recap, we: 157 | 158 | - wrote data-types for commands and responses and gave them 159 | `Serialize` instances, 160 | 161 | - wrote a handler that takes a command and returns a response, 162 | 163 | - ensured that our daemon is running with `ensureDaemonRunning`, and 164 | 165 | - sent commands and received responses with `runClient`. 166 | 167 | This tutorial illustrates the basic concepts behind `daemons`, but 168 | hides a powerful feature: the interface is *streaming*. See the 169 | [Queue](https://github.com/scvalex/daemons/blob/master/examples/Queue.hs) 170 | (Poor Man's Task Queue) tutorial for an example use of the streaming 171 | interface. 172 | -------------------------------------------------------------------------------- /examples/Name.hs: -------------------------------------------------------------------------------- 1 | {-# LANGUAGE DeriveGeneric, OverloadedStrings, MultiParamTypeClasses, FunctionalDependencies #-} 2 | 3 | module Main where 4 | 5 | import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar ) 6 | import Data.ByteString.Char8 ( ByteString, unpack ) 7 | import Data.Default ( def ) 8 | import Data.Serialize ( Serialize ) 9 | import Data.String ( fromString ) 10 | import qualified Data.Map as M 11 | import GHC.Generics 12 | import System.Environment ( getArgs ) 13 | import System.Daemon 14 | 15 | data CommandV0 = Register ByteString Port 16 | | WhereIs ByteString 17 | deriving ( Generic, Show ) 18 | 19 | instance Serialize CommandV0 20 | 21 | data Command = CommandV0 CommandV0 22 | deriving ( Generic, Show ) 23 | 24 | instance Serialize Command 25 | 26 | data ResponseV0 = Ok 27 | | NotFound ByteString 28 | | AtPort ByteString Port 29 | deriving ( Generic, Show ) 30 | 31 | instance Serialize ResponseV0 32 | 33 | data Response = ResponseV0 ResponseV0 34 | deriving ( Generic, Show ) 35 | 36 | instance Serialize Response 37 | 38 | type Registry = M.Map ByteString Port 39 | 40 | class VersionOf a b | a -> b where 41 | toLatest :: a -> b 42 | fromLatest :: b -> a 43 | 44 | instance VersionOf Command CommandV0 where 45 | toLatest (CommandV0 v0) = v0 46 | fromLatest v0 = CommandV0 v0 47 | 48 | instance VersionOf Response ResponseV0 where 49 | toLatest (ResponseV0 v0) = v0 50 | fromLatest v0 = ResponseV0 v0 51 | 52 | namePort :: Port 53 | namePort = 4370 54 | 55 | handleCommand :: MVar Registry -> CommandV0 -> IO ResponseV0 56 | handleCommand registryVar cmd = modifyMVar registryVar $ \registry -> return $ 57 | case cmd of 58 | WhereIs name -> ( registry 59 | , maybe (NotFound name) (AtPort name) (M.lookup name registry) ) 60 | Register name port -> ( M.insert name port registry 61 | , Ok ) 62 | 63 | wrapVersion :: (CommandV0 -> IO ResponseV0) -> Command -> IO Response 64 | wrapVersion f cmd = do 65 | rsp <- f (toLatest cmd) 66 | return (fromLatest rsp) 67 | 68 | main :: IO () 69 | main = do 70 | registryVar <- newMVar M.empty 71 | let options = def { daemonPort = namePort } 72 | ensureDaemonRunning "name" options (wrapVersion (handleCommand registryVar)) 73 | args <- getArgs 74 | let args' = map fromString args 75 | res <- case args' of 76 | ["where-is", key] -> 77 | runClient "localhost" namePort (CommandV0 (WhereIs key)) 78 | ["register", name, port] -> 79 | let portNum = read (unpack port) in 80 | runClient "localhost" namePort (CommandV0 (Register name portNum)) 81 | _ -> 82 | error "invalid command" 83 | print (fmap toLatest (res :: Maybe Response)) 84 | -------------------------------------------------------------------------------- /examples/Queue.hs: -------------------------------------------------------------------------------- 1 | {-# LANGUAGE DeriveGeneric, OverloadedStrings #-} 2 | 3 | module Main where 4 | 5 | import Control.Concurrent.Chan ( Chan, newChan, readChan, writeChan ) 6 | import Control.Concurrent.MVar ( MVar, newMVar, modifyMVar ) 7 | import Control.Monad ( forever ) 8 | import Control.Monad.Trans.Class ( lift ) 9 | import Control.Pipe.Serialize ( serializer, deserializer ) 10 | import Control.Pipe.Socket ( Handler ) 11 | import Data.ByteString.Char8 ( ByteString ) 12 | import qualified Data.ByteString.Char8 as B 13 | import Data.Char ( toLower ) 14 | import Data.Default ( def ) 15 | import Data.Serialize ( Serialize ) 16 | import Data.String ( fromString ) 17 | import qualified Data.Map as M 18 | import GHC.Generics 19 | import Network.Socket ( withSocketsDo ) 20 | import Pipes ( runEffect, (<-<), await, yield ) 21 | import System.Environment ( getArgs ) 22 | import System.Daemon 23 | import System.IO ( hPutStrLn, stderr ) 24 | 25 | data Command = Push ByteString ByteString 26 | | Pop ByteString 27 | | Consume ByteString 28 | deriving ( Generic, Show ) 29 | 30 | instance Serialize Command 31 | 32 | data Response = Value ByteString 33 | deriving ( Generic, Show ) 34 | 35 | instance Serialize Response 36 | 37 | type Registry = M.Map ByteString (Chan ByteString) 38 | 39 | handleCommands :: MVar Registry -> Handler () 40 | handleCommands registryVar reader writer = runEffect $ 41 | writer <-< serializer <-< commandExecuter <-< deserializer <-< reader 42 | where 43 | commandExecuter = forever $ do 44 | comm <- await 45 | case comm of 46 | Pop topic -> do 47 | ch <- lift $ getCreateChan topic 48 | transferToPipeFromChan ch 49 | Consume topic -> do 50 | ch <- lift $ getCreateChan topic 51 | forever $ transferToPipeFromChan ch 52 | Push topic val -> do 53 | ch <- lift $ getCreateChan topic 54 | lift $ writeChan ch val 55 | yield (Value "ok") 56 | 57 | -- Transfer a value from the given channel to the pipe. 58 | transferToPipeFromChan ch = do 59 | val <- lift $ readChan ch 60 | yield (Value val) 61 | 62 | -- Get the channel for the given topic, and create it if it does 63 | -- not already exist. 64 | getCreateChan topic = modifyMVar registryVar $ \registry -> do 65 | case M.lookup topic registry of 66 | Nothing -> do 67 | ch <- newChan 68 | return (M.insert topic ch registry, ch) 69 | Just ch -> do 70 | return (registry, ch) 71 | 72 | main :: IO () 73 | main = withSocketsDo $ do 74 | registryVar <- newMVar M.empty 75 | let options = def { daemonPort = 7857 } 76 | ensureDaemonWithHandlerRunning "queue" options (handleCommands registryVar) 77 | args <- getArgs 78 | let args' = map (fromString . map toLower) args 79 | case args' of 80 | ["pop", key] -> do 81 | res <- runClient "localhost" 7857 (Pop key) 82 | printResult res 83 | ["push", key, value] -> do 84 | res <- runClient "localhost" 7857 (Push key value) 85 | printResult res 86 | ["consume", key] -> do 87 | runClientWithHandler "localhost" 7857 $ \reader writer -> 88 | runEffect $ do 89 | writer <-< serializer <-< yield (Consume key) 90 | (forever $ await >>= \res -> lift (printResult (Just res))) 91 | <-< deserializer <-< reader 92 | _ -> do 93 | error "invalid command" 94 | where 95 | printResult :: Maybe Response -> IO () 96 | printResult Nothing = hPutStrLn stderr "no response" 97 | printResult (Just (Value val)) = B.putStrLn val 98 | -------------------------------------------------------------------------------- /flake.lock: -------------------------------------------------------------------------------- 1 | { 2 | "nodes": { 3 | "flake-compat": { 4 | "flake": false, 5 | "locked": { 6 | "lastModified": 1673956053, 7 | "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=", 8 | "owner": "edolstra", 9 | "repo": "flake-compat", 10 | "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9", 11 | "type": "github" 12 | }, 13 | "original": { 14 | "owner": "edolstra", 15 | "repo": "flake-compat", 16 | "type": "github" 17 | } 18 | }, 19 | "nixpkgs": { 20 | "locked": { 21 | "lastModified": 1695825837, 22 | "narHash": "sha256-4Ne11kNRnQsmSJCRSSNkFRSnHC4Y5gPDBIQGjjPfJiU=", 23 | "owner": "NixOS", 24 | "repo": "nixpkgs", 25 | "rev": "5cfafa12d57374f48bcc36fda3274ada276cf69e", 26 | "type": "github" 27 | }, 28 | "original": { 29 | "owner": "NixOS", 30 | "ref": "nixos-23.05", 31 | "repo": "nixpkgs", 32 | "type": "github" 33 | } 34 | }, 35 | "root": { 36 | "inputs": { 37 | "flake-compat": "flake-compat", 38 | "nixpkgs": "nixpkgs", 39 | "utils": "utils" 40 | } 41 | }, 42 | "systems": { 43 | "locked": { 44 | "lastModified": 1681028828, 45 | "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=", 46 | "owner": "nix-systems", 47 | "repo": "default", 48 | "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e", 49 | "type": "github" 50 | }, 51 | "original": { 52 | "owner": "nix-systems", 53 | "repo": "default", 54 | "type": "github" 55 | } 56 | }, 57 | "utils": { 58 | "inputs": { 59 | "systems": "systems" 60 | }, 61 | "locked": { 62 | "lastModified": 1694529238, 63 | "narHash": "sha256-zsNZZGTGnMOf9YpHKJqMSsa0dXbfmxeoJ7xHlrt+xmY=", 64 | "owner": "numtide", 65 | "repo": "flake-utils", 66 | "rev": "ff7b65b44d01cf9ba6a71320833626af21126384", 67 | "type": "github" 68 | }, 69 | "original": { 70 | "owner": "numtide", 71 | "repo": "flake-utils", 72 | "type": "github" 73 | } 74 | } 75 | }, 76 | "root": "root", 77 | "version": 7 78 | } 79 | -------------------------------------------------------------------------------- /flake.nix: -------------------------------------------------------------------------------- 1 | { 2 | inputs = { 3 | nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.05"; 4 | utils.url = "github:numtide/flake-utils"; 5 | flake-compat = { 6 | url = github:edolstra/flake-compat; 7 | flake = false; 8 | }; 9 | }; 10 | 11 | outputs = { self, nixpkgs, utils, ... }: 12 | utils.lib.eachDefaultSystem (system: 13 | let 14 | pkgs = import nixpkgs { inherit system; }; 15 | in 16 | { 17 | devShell = with pkgs; mkShell { 18 | buildInputs = [ 19 | cabal-install 20 | tokei 21 | 22 | haskell.compiler.ghc96 23 | haskellPackages.pipes 24 | ]; 25 | GIT_EXTERNAL_DIFF = "${difftastic}/bin/difft"; 26 | }; 27 | }); 28 | } 29 | -------------------------------------------------------------------------------- /src/Control/Pipe/C3.hs: -------------------------------------------------------------------------------- 1 | module Control.Pipe.C3 ( 2 | -- * Pipes 3 | commandSender, commandReceiver 4 | ) where 5 | 6 | import Control.Monad ( forever ) 7 | import Control.Monad.Trans.Class ( lift ) 8 | import Control.Pipe.Serialize ( serializer, deserializer ) 9 | import Control.Pipe.Socket ( Handler ) 10 | import Data.Serialize ( Serialize ) 11 | import Pipes ( runEffect, await, yield, (<-<) ) 12 | 13 | -- | Send a single command over the outgoing pipe and wait for a 14 | -- response. If the incoming pipe is closed before a response 15 | -- arrives, returns @Nothing@. 16 | commandSender :: (Serialize a, Serialize b) => a -> Handler (Maybe b) 17 | commandSender command reader writer = runEffect $ do 18 | writer <-< serializer <-< sendCommand 19 | receiveResponse 20 | <-< (deserializer >> return Nothing) 21 | <-< (reader >> return Nothing) 22 | where 23 | sendCommand = do 24 | yield command 25 | 26 | receiveResponse = do 27 | res <- await 28 | return (Just res) 29 | 30 | -- | Wait for commands on the incoming pipe, handle them, and send the 31 | -- reponses over the outgoing pipe. 32 | commandReceiver :: (Serialize a, Serialize b) => (a -> IO b) -> Handler () 33 | commandReceiver executeCommand reader writer = runEffect $ 34 | writer <-< serializer <-< commandExecuter <-< deserializer <-< reader 35 | where 36 | commandExecuter = forever $ do 37 | comm <- await 38 | yield =<< lift (executeCommand comm) 39 | -------------------------------------------------------------------------------- /src/Control/Pipe/Serialize.hs: -------------------------------------------------------------------------------- 1 | -- | This module provides the 'deserializer' and 'serializer' pipes to 2 | -- convert 'B.ByteString's off of pipes into typed values. 3 | -- 4 | -- In order to use it, the types of the values need to have 5 | -- 'Serialize' instances. These can be derived automatically using 6 | -- "Ghc.Generics": 7 | -- 8 | -- > {-# LANGUAGE DeriveGeneric #-} 9 | -- > 10 | -- > data Foo = Bar String | Baz Int 11 | -- > deriving ( Generic ) 12 | -- > 13 | -- > instance Serialize Foo 14 | -- 15 | -- Note that in the above example: we use the @DeriveGeneric@ 16 | -- extension, derive a @Generic@ instance for our data-type, and write 17 | -- an /empty/ @Serialize@ instance. 18 | -- 19 | module Control.Pipe.Serialize ( 20 | -- * Pipes 21 | serializer, deserializer 22 | ) where 23 | 24 | import Data.ByteString.Char8 ( ByteString ) 25 | import Data.Serialize ( Serialize, get, encode 26 | , Result(..), runGetPartial ) 27 | import Pipes ( Pipe, await, yield ) 28 | import Control.Monad ( forever ) 29 | 30 | -- | De-serialize data from strict 'ByteString's. Uses @cereal@'s 31 | -- incremental 'Data.Serialize.Get' parser. 32 | deserializer :: (Serialize a, Monad m, MonadFail m) => Pipe ByteString a m () 33 | deserializer = loop Nothing Nothing 34 | where 35 | loop mk mbin = do 36 | bin <- maybe await return mbin 37 | case (maybe (runGetPartial get) id mk) bin of 38 | Fail reason _leftover -> 39 | fail reason 40 | Partial k -> 41 | loop (Just k) Nothing 42 | Done c bin' -> do 43 | yield c 44 | loop Nothing (Just bin') 45 | 46 | -- | Serialize data into strict 'ByteString's. 47 | serializer :: (Serialize a, Monad m) => Pipe a ByteString m () 48 | serializer = forever $ do 49 | x <- await 50 | yield (encode x) 51 | -------------------------------------------------------------------------------- /src/Control/Pipe/Socket.hs: -------------------------------------------------------------------------------- 1 | {-# LANGUAGE ScopedTypeVariables #-} 2 | 3 | -- Thank you: 4 | -- pipes-network 5 | 6 | module Control.Pipe.Socket ( 7 | -- * Socket pipes 8 | socketReader, socketWriter, 9 | 10 | -- * Socket server/client 11 | Handler, runSocketServer, runSocketClient 12 | ) where 13 | 14 | import Control.Concurrent ( forkIO ) 15 | import qualified Control.Exception as CE 16 | import Control.Monad ( forever, unless ) 17 | import Control.Monad.IO.Class ( MonadIO(..) ) 18 | import Control.Monad.Trans.Class ( lift ) 19 | import Data.ByteString.Char8 ( ByteString ) 20 | import qualified Data.ByteString.Char8 as B 21 | import Network.Socket ( Socket ) 22 | import qualified Network.Socket as NS 23 | import Network.Socket.ByteString ( sendAll, recv ) 24 | import Pipes ( Consumer, Producer, await, yield ) 25 | 26 | -- | Stream data from the socket. 27 | socketReader :: (MonadIO m) => Socket -> Producer ByteString m () 28 | socketReader socket = do 29 | bin <- lift . liftIO $ recv socket 4096 30 | unless (B.null bin) $ do 31 | yield bin 32 | socketReader socket 33 | 34 | -- | Stream data to the socket. 35 | socketWriter :: (MonadIO m) => Socket -> Consumer ByteString m () 36 | socketWriter socket = forever $ do 37 | bin <- await 38 | lift . liftIO $ sendAll socket bin 39 | 40 | -- | A simple handler: takes an incoming stream of 'ByteString's, an 41 | -- stream of 'ByteString's, and ties them together somehow. 42 | -- Conceptually, the simplest handler would be @identity@: 43 | -- 44 | -- > import Control.Monad 45 | -- > import Control.Pipe 46 | -- > import Data.ByteString.Char8 47 | -- > 48 | -- > handler reader writer = do 49 | -- > let identity = forever $ do 50 | -- > x <- await 51 | -- > yield x 52 | -- > runPipe (writer <+< identity <+< reader) 53 | -- 54 | -- See the @pipes@ tutorial for more examples of writing pipes. 55 | -- 56 | -- Since 'ByteString's are fairly boring by themseleves, have a look 57 | -- at "Control.Pipe.Serialize" which lets you deserialize/serialize 58 | -- pipes of 'ByteString's easily. 59 | type Handler r = Producer ByteString IO () 60 | -> Consumer ByteString IO () 61 | -> IO r 62 | 63 | -- | Listen for connections on the given socket, and run 'Handler' on 64 | -- each received connection. The socket should previously have been 65 | -- bound to a port or to a file. Each handler is run in its own 66 | -- thread. Even in case of an error, the handlers' sockets are 67 | -- closed. 68 | runSocketServer :: (MonadIO m) => Socket -> Handler () -> m () 69 | runSocketServer lsocket handler = liftIO $ forever $ do 70 | (socket, _addr) <- NS.accept lsocket 71 | _ <- forkIO $ CE.finally 72 | (handler (socketReader socket) (socketWriter socket)) 73 | (NS.close socket) 74 | return () 75 | 76 | -- | Run 'Handler' on the given socket. 77 | runSocketClient :: (MonadIO m) => Socket -> Handler r -> m r 78 | runSocketClient socket handler = liftIO $ do 79 | handler (socketReader socket) (socketWriter socket) 80 | -------------------------------------------------------------------------------- /src/System/Daemon.hs: -------------------------------------------------------------------------------- 1 | -- | An RPC-like interface for daemons is provided by 2 | -- 'ensureDaemonRunning' and 'runClient'. 3 | -- 4 | -- A more versatile interface that lets you supply your own `Handler` 5 | -- is provided by `ensureDaemonWithHandlerRunning` and 6 | -- `runClientWithHandler`. These are useful if, for instance, you 7 | -- need streaming requests or replies, or if you need to change your 8 | -- event handler at runtime. 9 | -- 10 | -- The event handling loop is provided by `runInForeground`. You may 11 | -- want to use this for debugging purposes or if you want to handle 12 | -- daemonization manually. 13 | module System.Daemon ( 14 | -- * Daemons 15 | ensureDaemonRunning, ensureDaemonWithHandlerRunning, 16 | 17 | -- * Clients, 18 | runClient, runClientWithHandler, 19 | 20 | -- * Types 21 | DaemonOptions(..), PidFile(..), HostName, Port, 22 | 23 | -- * Helpers 24 | runInForeground, bindPort, getSocket 25 | ) where 26 | 27 | import Control.Concurrent ( threadDelay ) 28 | import qualified Control.Exception as CE 29 | import Control.Monad ( when ) 30 | import Control.Pipe.C3 ( commandSender, commandReceiver ) 31 | import Control.Pipe.Socket ( Handler, runSocketServer, runSocketClient ) 32 | import Data.Default ( Default(..) ) 33 | import Data.Serialize ( Serialize ) 34 | import Data.String ( IsString(..) ) 35 | import Network.Socket ( Socket, SockAddr(..), Family(..), SocketType(..) 36 | , SocketOption(..), setSocketOption 37 | , socket, close, connect, bind, listen 38 | , AddrInfo(..), getAddrInfo, addrAddress, defaultHints 39 | , defaultProtocol, tupleToHostAddress, maxListenQueue ) 40 | import System.Directory ( getHomeDirectory ) 41 | import System.FilePath ( (), (<.>) ) 42 | import System.Posix.Daemon ( runDetached, isRunning ) 43 | import Text.Printf ( printf ) 44 | 45 | type Port = Int 46 | type HostName = String 47 | 48 | -- | The configuration options of a daemon. See 'ensureDaemonRunning' 49 | -- for a description of each. 50 | data DaemonOptions = DaemonOptions 51 | { daemonPort :: Port 52 | , daemonPidFile :: PidFile 53 | , printOnDaemonStarted :: Bool 54 | } deriving ( Show ) 55 | 56 | instance Default DaemonOptions where 57 | def = DaemonOptions { daemonPort = 5000 58 | , daemonPidFile = InHome 59 | , printOnDaemonStarted = True 60 | } 61 | 62 | -- | The location of the daemon's pidfile. 63 | data PidFile = InHome 64 | | PidFile FilePath 65 | deriving ( Show ) 66 | 67 | instance IsString PidFile where 68 | fromString = PidFile 69 | 70 | -- | Simple wrapper around 'ensureDaemonWithHandlerRunning' which uses 71 | -- a simple function to respond to commands and doesn't deal with 72 | -- pipes. 73 | -- 74 | -- The @handler@ is just a function that takes a command and returns a 75 | -- response. 76 | ensureDaemonRunning :: (Serialize a, Serialize b) 77 | => String -- ^ name 78 | -> DaemonOptions -- ^ options 79 | -> (a -> IO b) -- ^ handler 80 | -> IO () 81 | ensureDaemonRunning name options executeCommand = do 82 | ensureDaemonWithHandlerRunning name options (commandReceiver executeCommand) 83 | 84 | -- FIXME Add set-up and tear-down action. The reason the threaded 85 | -- runtime wouldn't work was because we were creating the mvar in a 86 | -- different thread! 87 | 88 | -- | Start a daemon running on the given port, using the given handler 89 | -- to respond to events. If the daemon is already running, don't do 90 | -- anything. Returns immediately. 91 | -- 92 | -- The pidfile @PidFile options@ will be created and locked. This 93 | -- function checks the pidfile to see if the daemon is already 94 | -- running. 95 | -- 96 | -- The daemon will listen for incoming connections on all interfaces 97 | -- on @daemonPort options@. 98 | -- 99 | -- The @handler@ is a function that takes the reader and writer 100 | -- 'ByteString' pipes and does something with them. See 101 | -- 'commandReceiver' for an example handler. 102 | ensureDaemonWithHandlerRunning :: String -- ^ name 103 | -> DaemonOptions -- ^ options 104 | -> Handler () -- ^ handler 105 | -> IO () 106 | ensureDaemonWithHandlerRunning name options handler = do 107 | home <- getHomeDirectory 108 | let pidfile = case daemonPidFile options of 109 | InHome -> home ("." ++ name) <.> "pid" 110 | PidFile path -> path 111 | running <- isRunning pidfile 112 | when (not running) $ do 113 | runDetached (Just pidfile) def 114 | (runInForeground (daemonPort options) handler) 115 | when (printOnDaemonStarted options) 116 | (printf "Daemon started on port %d\n" (daemonPort options)) 117 | threadDelay (1 * 1000 * 1000) -- 1s delay 118 | 119 | -- | Start the given handler in the foreground. It will listen and 120 | -- respond to events on the given port. 121 | -- 122 | -- This is the function that 'ensureDaemonWithHandlerRunning' runs on 123 | -- the daemon thread. 124 | runInForeground :: Port -> Handler () -> IO () 125 | runInForeground port handler = do 126 | CE.bracket 127 | (bindPort port) 128 | close 129 | (\lsocket -> 130 | runSocketServer lsocket handler) 131 | 132 | -- | Send a command to the daemon running at the given network address 133 | -- and wait for a response. 134 | -- 135 | -- This is a simple wrapper around 'runClientWithHandler' that sends a 136 | -- single command and waits for a single response. 137 | -- 138 | -- If the connection is closed before receiving a response, return 139 | -- 'Nothing'. 140 | runClient :: (Serialize a, Serialize b) 141 | => HostName -- ^ hostname 142 | -> Port -- ^ port 143 | -> a -- ^ command 144 | -> IO (Maybe b) 145 | runClient hostname port comm = 146 | runClientWithHandler hostname port (commandSender comm) 147 | 148 | -- | Connect to the given network address and run the handler on the 149 | -- reader and wrier pipes for the socket. 150 | -- 151 | -- The @handler@ is a function that takes the reader and writer 152 | -- 'ByteString' pipes and does something with them. For an example 153 | -- handler, see 'commandSender', which sends a command and waits for a 154 | -- response. 155 | runClientWithHandler :: HostName -- ^ hostname 156 | -> Port -- ^ port 157 | -> Handler a -- ^ command 158 | -> IO a 159 | runClientWithHandler hostname port handler = do 160 | CE.bracket 161 | (getSocket hostname port) 162 | close 163 | (\s -> runSocketClient s handler) 164 | 165 | -- | Create a socket and bind it to the given port. 166 | bindPort :: Port -> IO Socket 167 | bindPort port = do 168 | CE.bracketOnError 169 | (socket AF_INET Stream defaultProtocol) 170 | close 171 | (\s -> do 172 | -- FIXME See the examples at the end of Network.Socket.ByteString 173 | setSocketOption s ReuseAddr 1 174 | bind s (SockAddrInet (fromIntegral port) (tupleToHostAddress (0, 0, 0, 0))) 175 | listen s maxListenQueue 176 | return s) 177 | 178 | -- | Create a socket connected to the given network address. 179 | getSocket :: HostName -> Port -> IO Socket 180 | getSocket hostname port = do 181 | addrInfos <- getAddrInfo (Just (defaultHints { addrFamily = AF_INET })) 182 | (Just hostname) 183 | (Just $ show port) 184 | CE.bracketOnError 185 | (socket AF_INET Stream defaultProtocol) 186 | close 187 | (\s -> do 188 | connect s (addrAddress $ head addrInfos) 189 | return s) 190 | -------------------------------------------------------------------------------- /src/System/Posix/Daemon.hs: -------------------------------------------------------------------------------- 1 | -- | This module provides a simple interface to creating, checking the 2 | -- status of, and stopping background jobs. 3 | -- 4 | -- Use 'runDetached' to start a background job. For instance, here is 5 | -- a daemon that peridically hits a webserver: 6 | -- 7 | -- > import Control.Concurrent 8 | -- > import Control.Monad 9 | -- > import Data.Default 10 | -- > import Data.Maybe 11 | -- > import Network.BSD 12 | -- > import Network.HTTP 13 | -- > import Network.URI 14 | -- > import System.Posix.Daemon 15 | -- > 16 | -- > main :: IO () 17 | -- > main = runDetached (Just "diydns.pid") def $ forever $ do 18 | -- > hostname <- getHostName 19 | -- > _ <- simpleHTTP 20 | -- > (Request { rqURI = fromJust (parseURI "http://foo.com/dns") 21 | -- > , rqMethod = GET 22 | -- > , rqHeaders = [] 23 | -- > , rqBody = hostname }) 24 | -- > threadDelay (600 * 1000 * 1000) 25 | -- 26 | -- To check if the above job is running, use 'isRunning' with the same 27 | -- pidfile: 28 | -- 29 | -- > isRunning "diydns.pid" 30 | -- 31 | -- Finally, to stop the above job (maybe because we're rolling a new 32 | -- version of it), use 'kill': 33 | -- 34 | -- > kill "diydns.pid" 35 | -- 36 | -- To stop a job and wait for it to close (and release its pidfile), use 37 | -- 'killAndWait': 38 | -- 39 | -- > killAndWait "diydns.pid" >> doSomething 40 | -- 41 | -- As a side note, the code above is a script that the author uses as 42 | -- a sort of homebrew dynamic DNS: the remote address is a CGI script 43 | -- that records the IP addresses of all incoming requests in separate 44 | -- files named after the contents of the requests; the addresses are 45 | -- then viewable with any browser. 46 | module System.Posix.Daemon ( 47 | -- * Starting 48 | runDetached, Redirection(..), 49 | 50 | -- * Status 51 | isRunning, 52 | 53 | -- * Stopping 54 | kill, killAndWait, brutalKill 55 | ) where 56 | 57 | import Prelude hiding ( FilePath ) 58 | 59 | import Control.Monad ( when ) 60 | import Data.ByteString.Char8 ( unpack ) 61 | import Data.Default ( Default(..) ) 62 | import System.Directory ( doesFileExist ) 63 | import System.FilePath ( FilePath ) 64 | import System.IO ( SeekMode(..), hFlush, stdout ) 65 | import System.Posix.Files ( stdFileMode ) 66 | import System.Posix.IO ( openFd, OpenMode(..), defaultFileFlags, closeFd 67 | , dupTo, stdInput, stdOutput, stdError, getLock 68 | , createFile, fdWrite 69 | , LockRequest (..), setLock, waitToSetLock, creat ) 70 | import System.Posix.IO.ByteString ( fdRead ) 71 | import System.Posix.Process ( getProcessID, forkProcess, createSession ) 72 | import System.Posix.Signals ( Signal, signalProcess, sigQUIT, sigKILL ) 73 | 74 | -- | Where should the output (and input) of a daemon be redirected to? 75 | -- (we can't just leave it to the current terminal, because it may be 76 | -- closed, and that would kill the daemon). 77 | -- 78 | -- When in doubt, just use 'def', the default value. 79 | -- 80 | -- 'DevNull' causes the output to be redirected to @\/dev\/null@. This 81 | -- is safe and is what you want in most cases. 82 | -- 83 | -- If you don't want to lose the output (maybe because you're using it 84 | -- for logging), use 'ToFile', instead. 85 | data Redirection = DevNull 86 | | ToFile FilePath 87 | deriving ( Show ) 88 | 89 | instance Default Redirection where 90 | def = DevNull 91 | 92 | -- | Run the given action detached from the current terminal; this 93 | -- creates an entirely new process. This function returns 94 | -- immediately. Uses the double-fork technique to create a well 95 | -- behaved daemon. If @pidfile@ is given, check/write it; if we 96 | -- cannot obtain a lock on the file, another process is already using 97 | -- it, so fail. The @redirection@ parameter controls what to do with 98 | -- the standard channels (@stdin@, @stderr@, and @stdout@). 99 | -- 100 | -- See: 101 | -- 102 | -- Note: All unnecessary fds should be close before calling this. 103 | -- Otherwise, you get an fd leak. 104 | runDetached :: Maybe FilePath -- ^ pidfile 105 | -> Redirection -- ^ redirection 106 | -> IO () -- ^ program 107 | -> IO () 108 | runDetached maybePidFile redirection program = do 109 | -- check if the pidfile exists; fail if it does 110 | checkPidFile 111 | -- fork first child 112 | ignore $ forkProcess $ do 113 | -- create a new session and make this process its leader; see 114 | -- setsid(2) 115 | ignore $ createSession 116 | -- fork second child 117 | ignore $ forkProcess $ do 118 | -- create the pidfile 119 | writePidFile 120 | -- remap standard fds 121 | remapFds 122 | -- run the daemon 123 | program 124 | where 125 | ignore act = act >> return () 126 | 127 | -- Remap the standard channels based on the @redirection@ 128 | -- parameter. 129 | remapFds = do 130 | devnull <- openFd "/dev/null" ReadOnly defaultFileFlags 131 | ignore (dupTo devnull stdInput) 132 | closeFd devnull 133 | 134 | let file = case redirection of 135 | DevNull -> "/dev/null" 136 | ToFile filepath -> filepath 137 | fd <- openFd file ReadWrite defaultFileFlags { creat = Just stdFileMode } 138 | hFlush stdout 139 | mapM_ (dupTo fd) [stdOutput, stdError] 140 | closeFd fd 141 | 142 | -- Convert the 'FilePath' @pidfile@ to a regular 'String' and run 143 | -- the action with it. 144 | withPidFile act = 145 | case maybePidFile of 146 | Nothing -> return () 147 | Just pidFile -> act pidFile 148 | 149 | -- Check if the pidfile exists; fail if it does, and create it, otherwise 150 | checkPidFile = withPidFile $ \pidFile -> do 151 | running <- isRunning pidFile 152 | when running $ fail "already running" 153 | 154 | writePidFile = withPidFile $ \pidFile -> do 155 | fd <- createFile pidFile stdFileMode 156 | setLock fd (WriteLock, AbsoluteSeek, 0, 0) 157 | pid <- getProcessID 158 | ignore $ fdWrite fd (show pid) 159 | -- note that we do not close the fd; doing so would release 160 | -- the lock 161 | 162 | -- | Return 'True' if the given file is locked by a process. In our 163 | -- case, returns 'True' when the daemon that created the file is still 164 | -- alive. 165 | isRunning :: FilePath -> IO Bool 166 | isRunning pidFile = do 167 | dfe <- doesFileExist pidFile 168 | if dfe 169 | then do 170 | fd <- openFd pidFile ReadWrite defaultFileFlags 171 | -- is there an *incompatible* lock on the pidfile? 172 | ml <- getLock fd (WriteLock, AbsoluteSeek, 0, 0) 173 | pid <- fdRead fd 100 >>= \x -> return (unpack x) 174 | closeFd fd 175 | case ml of 176 | Nothing -> do 177 | pid' <- getProcessID 178 | return (read pid == pid') 179 | Just _ -> do 180 | return True 181 | else do 182 | return False 183 | 184 | -- | Send 'sigQUIT' to the process recorded in the pidfile. This 185 | -- gives the process a chance to close cleanly. 186 | kill :: FilePath -> IO () 187 | kill = signalProcessByFilePath sigQUIT 188 | 189 | -- | Kill a process and wait for it to release its pidfile 190 | killAndWait :: FilePath -> IO () 191 | killAndWait pidFile = do 192 | signalProcessByFilePath sigQUIT pidFile 193 | fd <- openFd pidFile ReadWrite defaultFileFlags 194 | waitToSetLock fd (WriteLock, AbsoluteSeek, 0, 0) 195 | closeFd fd 196 | 197 | -- | Send 'sigKILL' to the process recorded in the pidfile. This 198 | -- immediately kills the process. 199 | brutalKill :: FilePath -> IO () 200 | brutalKill = signalProcessByFilePath sigKILL 201 | 202 | -- | Send a signal to a process whose pid is recorded in a file. 203 | signalProcessByFilePath :: Signal -> FilePath -> IO () 204 | signalProcessByFilePath signal pidFile = do 205 | pid <- readFile pidFile 206 | signalProcess signal (read pid) 207 | -------------------------------------------------------------------------------- /stack.yaml: -------------------------------------------------------------------------------- 1 | # This file was automatically generated by 'stack init' 2 | # 3 | # Some commonly used options have been documented as comments in this file. 4 | # For advanced use and comprehensive documentation of the format, please see: 5 | # https://docs.haskellstack.org/en/stable/yaml_configuration/ 6 | 7 | # Resolver to choose a 'specific' stackage snapshot or a compiler version. 8 | # A snapshot resolver dictates the compiler version and the set of packages 9 | # to be used for project dependencies. For example: 10 | # 11 | # resolver: lts-3.5 12 | # resolver: nightly-2015-09-21 13 | # resolver: ghc-7.10.2 14 | # 15 | # The location of a snapshot can be provided as a file or url. Stack assumes 16 | # a snapshot provided as a file might change, whereas a url resource does not. 17 | # 18 | # resolver: ./custom-snapshot.yaml 19 | # resolver: https://example.com/snapshots/2018-01-01.yaml 20 | resolver: lts-14.22 21 | 22 | # User packages to be built. 23 | # Various formats can be used as shown in the example below. 24 | # 25 | # packages: 26 | # - some-directory 27 | # - https://example.com/foo/bar/baz-0.0.2.tar.gz 28 | # subdirs: 29 | # - auto-update 30 | # - wai 31 | packages: 32 | - . 33 | # Dependency packages to be pulled from upstream that are not in the resolver. 34 | # These entries can reference officially published versions as well as 35 | # forks / in-progress versions pinned to a git hash. For example: 36 | # 37 | # extra-deps: 38 | # - acme-missiles-0.3 39 | # - git: https://github.com/commercialhaskell/stack.git 40 | # commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a 41 | # 42 | # extra-deps: [] 43 | 44 | # Override default flag values for local packages and extra-deps 45 | # flags: {} 46 | 47 | # Extra package databases containing global packages 48 | # extra-package-dbs: [] 49 | 50 | # Control whether we use the GHC we find on the path 51 | # system-ghc: true 52 | # 53 | # Require a specific version of stack, using version ranges 54 | # require-stack-version: -any # Default 55 | # require-stack-version: ">=2.1" 56 | # 57 | # Override the architecture used by stack, especially useful on Windows 58 | # arch: i386 59 | # arch: x86_64 60 | # 61 | # Extra directories used by stack for building 62 | # extra-include-dirs: [/path/to/dir] 63 | # extra-lib-dirs: [/path/to/dir] 64 | # 65 | # Allow a newer minor version of GHC than the snapshot specifies 66 | # compiler-check: newer-minor 67 | -------------------------------------------------------------------------------- /stack.yaml.lock: -------------------------------------------------------------------------------- 1 | # This file was autogenerated by Stack. 2 | # You should not edit this file by hand. 3 | # For more information, please see the documentation at: 4 | # https://docs.haskellstack.org/en/stable/lock_files 5 | 6 | packages: [] 7 | snapshots: 8 | - completed: 9 | size: 524164 10 | url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/14/22.yaml 11 | sha256: 7ad8f33179b32d204165a3a662c6269464a47a7e65a30abc38d01b5a38ec42c0 12 | original: lts-14.22 13 | -------------------------------------------------------------------------------- /test/Daemon.hs: -------------------------------------------------------------------------------- 1 | {-# LANGUAGE OverloadedStrings, ScopedTypeVariables #-} 2 | 3 | module Main where 4 | 5 | import Control.Concurrent 6 | import Control.Exception 7 | import Control.Monad 8 | import Data.Default 9 | import System.Directory 10 | import System.Posix.Daemon 11 | import System.Posix.Process 12 | 13 | import Test.Framework 14 | import Test.Framework.Providers.HUnit 15 | import Test.HUnit 16 | 17 | main :: IO () 18 | main = defaultMainWithOpts 19 | [ testCase "firstRun" testFirst 20 | , testCase "withPid" testWithPid 21 | , testCase "isRunning" testIsRunning 22 | , testCase "exclusion" testExclusion 23 | , testCase "release" testRelease 24 | , testCase "redirection" testRedirection 25 | ] mempty 26 | 27 | ensureRemoved :: [FilePath] -> IO () 28 | ensureRemoved filepaths = forM_ filepaths $ \filepath -> do 29 | exists <- doesFileExist filepath 30 | when exists $ do 31 | removeFile filepath 32 | 33 | -- Wait the given number of ms. 34 | sleep :: Int -> IO () 35 | sleep n = threadDelay (n * 1000) 36 | 37 | testFirst :: Assertion 38 | testFirst = flip finally (ensureRemoved ["tmp"]) $ do 39 | let txtExp = "42" 40 | runDetached Nothing def $ do 41 | writeFile "tmp" txtExp 42 | sleep 500 43 | txt <- readFile "tmp" 44 | txt @?= txtExp 45 | 46 | testWithPid :: Assertion 47 | testWithPid = flip finally (ensureRemoved ["pid", "tmp"]) $ do 48 | let txtExp = "42" 49 | runDetached (Just "pid") def $ do 50 | pid <- getProcessID 51 | pid' <- readFile "pid" 52 | if show pid == pid' 53 | then writeFile "tmp" txtExp 54 | else writeFile "tmp" "wrong pid recorded" 55 | sleep 500 56 | txt <- readFile "tmp" 57 | txt @?= txtExp 58 | pid <- readFile "pid" 59 | null pid @?= False 60 | 61 | testIsRunning :: Assertion 62 | testIsRunning = flip finally (ensureRemoved ["pid", "tmp"]) $ do 63 | runDetached (Just "pid") def $ do 64 | running <- isRunning "pid" 65 | writeFile "tmp" (show running) 66 | sleep 10000 67 | sleep 500 68 | 69 | -- FIXME There's some weird behaviour when the process that has locked 70 | -- the file (or its ancestors, or its descendents) use 'isRunning'. 71 | -- 72 | -- The semantics of 'fnctl' are "try to aquire the requested lock; if 73 | -- there is an incompatible lock in place, return it". Of course, 74 | -- this means that the process that acquired the lock sees it as 75 | -- unlocked. 76 | -- 77 | -- We mitigated the obvious part of the problem (same process) by 78 | -- checking the pid in the pidfile. Now, we're left with the case 79 | -- where an ancestor of the process thinks it can set the lock. 80 | 81 | -- running <- isRunning "pid" 82 | -- running @?= True 83 | txt <- readFile "tmp" 84 | txt @?= "True" 85 | 86 | testExclusion :: Assertion 87 | testExclusion = flip finally (ensureRemoved ["pid", "tmp"]) $ do 88 | let txtExp = "ok" 89 | runDetached (Just "pid") def $ do 90 | sleep 1000 91 | sleep 500 92 | handle (\(_ :: SomeException) -> writeFile "tmp" txtExp) 93 | (runDetached (Just "pid") def $ do 94 | writeFile "tmp" "failed") 95 | sleep 500 96 | txt <- readFile "tmp" 97 | txt @?= txtExp 98 | 99 | testRelease :: Assertion 100 | testRelease = flip finally (ensureRemoved ["pid", "tmp"]) $ do 101 | let txtExp = "ok" 102 | runDetached (Just "pid") def $ do 103 | writeFile "tmp" txtExp 104 | sleep 500 105 | txt <- readFile "tmp" 106 | txt @?= txtExp 107 | let txtExp' = "ok" 108 | runDetached (Just "pid") def $ do 109 | writeFile "tmp" txtExp' 110 | sleep 500 111 | txt' <- readFile "tmp" 112 | txt' @?= txtExp' 113 | 114 | testRedirection :: Assertion 115 | testRedirection = flip finally (ensureRemoved ["tmp"]) $ do 116 | let txtExp = "ok" 117 | runDetached Nothing (ToFile "tmp") $ do 118 | putStr "ok" 119 | sleep 500 120 | txt <- readFile "tmp" 121 | txt @?= txtExp 122 | --------------------------------------------------------------------------------