Synnefo » snf-ganeti

{-| Implementation of the generic daemon functionality.

-}

{-

Copyright (C) 2011, 2012 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Daemon

  ( DaemonOptions(..)

  , OptType

  , defaultOptions

  , oShowHelp

  , oShowVer

  , oNoDaemonize

  , oNoUserChecks

  , oDebug

  , oPort

  , parseArgs

  , writePidFile

  , genericMain

  ) where

import Control.Monad

import qualified Data.Version

import Data.Word

import System.Console.GetOpt

import System.Exit

import System.Environment

import System.Info

import System.IO

import System.Posix.Directory

import System.Posix.Files

import System.Posix.IO

import System.Posix.Process

import System.Posix.Types

import Text.Printf

import Ganeti.Logging

import Ganeti.Runtime

import Ganeti.BasicTypes

import Ganeti.HTools.Utils

import qualified Ganeti.HTools.Version as Version(version)

import qualified Ganeti.Constants as C

-- * Data types

-- | Command line options structure.

data DaemonOptions = DaemonOptions

  { optShowHelp     :: Bool           -- ^ Just show the help

  , optShowVer      :: Bool           -- ^ Just show the program version

  , optDaemonize    :: Bool           -- ^ Whether to daemonize or not

  , optPort         :: Maybe Word16   -- ^ Override for the network port

  , optDebug        :: Bool           -- ^ Enable debug messages

  , optNoUserChecks :: Bool           -- ^ Ignore user checks

  }

-- | Default values for the command line options.

defaultOptions :: DaemonOptions

defaultOptions  = DaemonOptions

  { optShowHelp     = False

  , optShowVer      = False

  , optDaemonize    = True

  , optPort         = Nothing

  , optDebug        = False

  , optNoUserChecks = False

  }

-- | Abrreviation for the option type.

type OptType = OptDescr (DaemonOptions -> Result DaemonOptions)

-- | Helper function for required arguments which need to be converted

-- as opposed to stored just as string.

reqWithConversion :: (String -> Result a)

                  -> (a -> DaemonOptions -> Result DaemonOptions)

                  -> String

                  -> ArgDescr (DaemonOptions -> Result DaemonOptions)

reqWithConversion conversion_fn updater_fn metavar =

  ReqArg (\string_opt opts -> do

            parsed_value <- conversion_fn string_opt

            updater_fn parsed_value opts) metavar

-- * Command line options

oShowHelp :: OptType

oShowHelp = Option "h" ["help"]

            (NoArg (\ opts -> Ok opts { optShowHelp = True}))

            "Show the help message and exit"

oShowVer :: OptType

oShowVer = Option "V" ["version"]

           (NoArg (\ opts -> Ok opts { optShowVer = True}))

           "Show the version of the program and exit"

oNoDaemonize :: OptType

oNoDaemonize = Option "f" ["foreground"]

               (NoArg (\ opts -> Ok opts { optDaemonize = False}))

               "Don't detach from the current terminal"

oDebug :: OptType

oDebug = Option "d" ["debug"]

         (NoArg (\ opts -> Ok opts { optDebug = True }))

         "Enable debug messages"

oNoUserChecks :: OptType

oNoUserChecks = Option "" ["no-user-checks"]

         (NoArg (\ opts -> Ok opts { optNoUserChecks = True }))

         "Ignore user checks"

oPort :: Int -> OptType

oPort def = Option "p" ["--port"]

            (reqWithConversion (tryRead "reading port")

             (\port opts -> Ok opts { optPort = Just port }) "PORT")

            ("Network port (default: " ++ show def ++ ")")

-- | Usage info.

usageHelp :: String -> [OptType] -> String

usageHelp progname =

  usageInfo (printf "%s %s\nUsage: %s [OPTION...]"

             progname Version.version progname)

-- | Command line parser, using the 'Options' structure.

parseOpts :: [String]               -- ^ The command line arguments

          -> String                 -- ^ The program name

          -> [OptType]              -- ^ The supported command line options

          -> IO (DaemonOptions, [String]) -- ^ The resulting options

                                          -- and leftover arguments

parseOpts argv progname options =

  case getOpt Permute options argv of

    (opt_list, args, []) ->

      do

        parsed_opts <-

          case foldM (flip id) defaultOptions opt_list of

            Bad msg -> do

              hPutStrLn stderr "Error while parsing command\

                               \line arguments:"

              hPutStrLn stderr msg

              exitWith $ ExitFailure 1

            Ok val -> return val

        return (parsed_opts, args)

    (_, _, errs) -> do

      hPutStrLn stderr $ "Command line error: "  ++ concat errs

      hPutStrLn stderr $ usageHelp progname options

      exitWith $ ExitFailure 2

-- | Small wrapper over getArgs and 'parseOpts'.

parseArgs :: String -> [OptType] -> IO (DaemonOptions, [String])

parseArgs cmd options = do

  cmd_args <- getArgs

  parseOpts cmd_args cmd options

-- * Daemon-related functions

-- | PID file mode.

pidFileMode :: FileMode

pidFileMode = unionFileModes ownerReadMode ownerWriteMode

-- | Writes a PID file and locks it.

_writePidFile :: FilePath -> IO Fd

_writePidFile path = do

  fd <- createFile path pidFileMode

  setLock fd (WriteLock, AbsoluteSeek, 0, 0)

  my_pid <- getProcessID

  _ <- fdWrite fd (show my_pid ++ "\n")

  return fd

-- | Wrapper over '_writePidFile' that transforms IO exceptions into a

-- 'Bad' value.

writePidFile :: FilePath -> IO (Result Fd)

writePidFile path = do

  catch (fmap Ok $ _writePidFile path) (return . Bad . show)

-- | Sets up a daemon's environment.

setupDaemonEnv :: FilePath -> FileMode -> IO ()

setupDaemonEnv cwd umask = do

  changeWorkingDirectory cwd

  _ <- setFileCreationMask umask

  _ <- createSession

  return ()

-- | Run an I/O action as a daemon.

--

-- WARNING: this only works in single-threaded mode (either using the

-- single-threaded runtime, or using the multi-threaded one but with

-- only one OS thread, i.e. -N1).

--

-- FIXME: this doesn't support error reporting and the prepfn

-- functionality.

daemonize :: IO () -> IO ()

daemonize action = do

  -- first fork

  _ <- forkProcess $ do

    -- in the child

    setupDaemonEnv "/" (unionFileModes groupModes otherModes)

    _ <- forkProcess action

    exitImmediately ExitSuccess

  exitImmediately ExitSuccess

-- | Generic daemon startup.

genericMain :: GanetiDaemon -> [OptType] -> (DaemonOptions -> IO ()) -> IO ()

genericMain daemon options main = do

  let progname = daemonName daemon

  (opts, args) <- parseArgs progname options

  when (optShowHelp opts) $ do

    putStr $ usageHelp progname options

    exitWith ExitSuccess

  when (optShowVer opts) $ do

    printf "%s %s\ncompiled with %s %s\nrunning on %s %s\n"

           progname Version.version

           compilerName (Data.Version.showVersion compilerVersion)

           os arch :: IO ()

    exitWith ExitSuccess

  unless (null args) $ do

         hPutStrLn stderr "This program doesn't take any arguments"

         exitWith $ ExitFailure C.exitFailure

  unless (optNoUserChecks opts) $ do

    runtimeEnts <- getEnts

    case runtimeEnts of

      Bad msg -> do

        hPutStrLn stderr $ "Can't find required user/groups: " ++ msg

        exitWith $ ExitFailure C.exitFailure

      Ok ents -> verifyDaemonUser daemon ents

  let processFn = if optDaemonize opts then daemonize else id

  processFn $ innerMain daemon opts (main opts)

-- | Inner daemon function.

--

-- This is executed after daemonization.

innerMain :: GanetiDaemon -> DaemonOptions -> IO () -> IO ()

innerMain daemon opts main = do

  setupLogging (daemonLogFile daemon) (daemonName daemon) (optDebug opts)

                 (not (optDaemonize opts)) False

  pid_fd <- writePidFile (daemonPidFile daemon)

  case pid_fd of

    Bad msg -> do

         hPutStrLn stderr $ "Cannot write PID file; already locked? Error: " ++

                   msg

         exitWith $ ExitFailure 1

    _ -> return ()

  logNotice "starting"

  main