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

  , CheckFn

  , PrepFn

  , MainFn

  , defaultOptions

  , oShowHelp

  , oShowVer

  , oNoDaemonize

  , oNoUserChecks

  , oDebug

  , oPort

  , oBindAddress

  , oSyslogUsage

  , parseArgs

  , parseAddress

  , cleanupSocket

  , describeError

  , genericMain

  ) where

import Control.Exception

import Control.Monad

import Data.Maybe (fromMaybe)

import Data.Word

import GHC.IO.Handle (hDuplicateTo)

import qualified Network.Socket as Socket

import System.Console.GetOpt

import System.Exit

import System.Environment

import System.IO

import System.IO.Error (isDoesNotExistError, modifyIOError, annotateIOError)

import System.Posix.Directory

import System.Posix.Files

import System.Posix.IO

import System.Posix.Process

import System.Posix.Types

import System.Posix.Signals

import Ganeti.Common as Common

import Ganeti.Logging

import Ganeti.Runtime

import Ganeti.BasicTypes

import Ganeti.Utils

import qualified Ganeti.Constants as C

import qualified Ganeti.Ssconf as Ssconf

-- * Constants

-- | \/dev\/null path.

devNull :: FilePath

devNull = "/dev/null"

-- | Error message prefix, used in two separate paths (when forking

-- and when not).

daemonStartupErr :: String -> String

daemonStartupErr = ("Error when starting the daemon process: " ++)

-- * Data types

-- | Command line options structure.

data DaemonOptions = DaemonOptions

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

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

  , optShowComp     :: Bool           -- ^ Just show the completion info

  , 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

  , optBindAddress  :: Maybe String   -- ^ Override for the bind address

  , optSyslogUsage  :: Maybe SyslogUsage -- ^ Override for Syslog usage

  }

-- | Default values for the command line options.

defaultOptions :: DaemonOptions

defaultOptions  = DaemonOptions

  { optShowHelp     = False

  , optShowVer      = False

  , optShowComp     = False

  , optDaemonize    = True

  , optPort         = Nothing

  , optDebug        = False

  , optNoUserChecks = False

  , optBindAddress  = Nothing

  , optSyslogUsage  = Nothing

  }

instance StandardOptions DaemonOptions where

  helpRequested = optShowHelp

  verRequested  = optShowVer

  compRequested = optShowComp

  requestHelp o = o { optShowHelp = True }

  requestVer  o = o { optShowVer  = True }

  requestComp o = o { optShowComp = True }

-- | Abrreviation for the option type.

type OptType = GenericOptType DaemonOptions

-- | Check function type.

type CheckFn a = DaemonOptions -> IO (Either ExitCode a)

-- | Prepare function type.

type PrepFn a b = DaemonOptions -> a -> IO b

-- | Main execution function type.

type MainFn a b = DaemonOptions -> a -> b -> IO ()

-- * Command line options

oNoDaemonize :: OptType

oNoDaemonize =

  (Option "f" ["foreground"]

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

   "Don't detach from the current terminal",

   OptComplNone)

oDebug :: OptType

oDebug =

  (Option "d" ["debug"]

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

   "Enable debug messages",

   OptComplNone)

oNoUserChecks :: OptType

oNoUserChecks =

  (Option "" ["no-user-checks"]

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

   "Ignore user checks",

   OptComplNone)

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 ++ ")"),

   OptComplInteger)

oBindAddress :: OptType

oBindAddress =

  (Option "b" ["bind"]

   (ReqArg (\addr opts -> Ok opts { optBindAddress = Just addr })

    "ADDR")

   "Bind address (default depends on cluster configuration)",

   OptComplInetAddr)

oSyslogUsage :: OptType

oSyslogUsage =

  (Option "" ["syslog"]

   (reqWithConversion syslogUsageFromRaw

    (\su opts -> Ok opts { optSyslogUsage = Just su })

    "SYSLOG")

   ("Enable logging to syslog (except debug \

    \messages); one of 'no', 'yes' or 'only' [" ++ C.syslogUsage ++

    "]"),

   OptComplChoices ["yes", "no", "only"])

-- | Generic options.

genericOpts :: [OptType]

genericOpts = [ oShowHelp

              , oShowVer

              , oShowComp

              ]

-- | Annotates and transforms IOErrors into a Result type. This can be

-- used in the error handler argument to 'catch', for example.

ioErrorToResult :: String -> IOError -> IO (Result a)

ioErrorToResult description exc =

  return . Bad $ description ++ ": " ++ show exc

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

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

parseArgs cmd options = do

  cmd_args <- getArgs

  parseOpts defaultOptions cmd_args cmd (options ++ genericOpts) []

-- * 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

-- | Helper function to ensure a socket doesn't exist. Should only be

-- called once we have locked the pid file successfully.

cleanupSocket :: FilePath -> IO ()

cleanupSocket socketPath =

  catchJust (guard . isDoesNotExistError) (removeLink socketPath)

            (const $ return ())

-- | Sets up a daemon's environment.

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

setupDaemonEnv cwd umask = do

  changeWorkingDirectory cwd

  _ <- setFileCreationMask umask

  _ <- createSession

  return ()

-- | Signal handler for reopening log files.

handleSigHup :: FilePath -> IO ()

handleSigHup path = do

  setupDaemonFDs (Just path)

  logInfo "Reopening log files after receiving SIGHUP"

-- | Sets up a daemon's standard file descriptors.

setupDaemonFDs :: Maybe FilePath -> IO ()

setupDaemonFDs logfile = do

  null_in_handle <- openFile devNull ReadMode

  null_out_handle <- openFile (fromMaybe devNull logfile) AppendMode

  hDuplicateTo null_in_handle stdin

  hDuplicateTo null_out_handle stdout

  hDuplicateTo null_out_handle stderr

  hClose null_in_handle

  hClose null_out_handle

-- | Computes the default bind address for a given family.

defaultBindAddr :: Int                  -- ^ The port we want

                -> Socket.Family        -- ^ The cluster IP family

                -> Result (Socket.Family, Socket.SockAddr)

defaultBindAddr port Socket.AF_INET =

  Ok (Socket.AF_INET,

      Socket.SockAddrInet (fromIntegral port) Socket.iNADDR_ANY)

defaultBindAddr port Socket.AF_INET6 =

  Ok (Socket.AF_INET6,

      Socket.SockAddrInet6 (fromIntegral port) 0 Socket.iN6ADDR_ANY 0)

defaultBindAddr _ fam = Bad $ "Unsupported address family: " ++ show fam

-- | Default hints for the resolver

resolveAddrHints :: Maybe Socket.AddrInfo

resolveAddrHints =

  Just Socket.defaultHints { Socket.addrFlags = [Socket.AI_NUMERICHOST,

                                                 Socket.AI_NUMERICSERV] }

-- | Resolves a numeric address.

resolveAddr :: Int -> String -> IO (Result (Socket.Family, Socket.SockAddr))

resolveAddr port str = do

  resolved <- Socket.getAddrInfo resolveAddrHints (Just str) (Just (show port))

  return $ case resolved of

             [] -> Bad "Invalid results from lookup?"

             best:_ -> Ok (Socket.addrFamily best, Socket.addrAddress best)

-- | Based on the options, compute the socket address to use for the

-- daemon.

parseAddress :: DaemonOptions      -- ^ Command line options

             -> Int                -- ^ Default port for this daemon

             -> IO (Result (Socket.Family, Socket.SockAddr))

parseAddress opts defport = do

  let port = maybe defport fromIntegral $ optPort opts

  def_family <- Ssconf.getPrimaryIPFamily Nothing

  case optBindAddress opts of

    Nothing -> return (def_family >>= defaultBindAddr port)

    Just saddr -> Control.Exception.catch

                    (resolveAddr port saddr)

                    (ioErrorToResult $ "Invalid address " ++ saddr)

-- | Run an I\/O action that might throw an I\/O error, under a

-- handler that will simply annotate and re-throw the exception.

describeError :: String -> Maybe Handle -> Maybe FilePath -> IO a -> IO a

describeError descr hndl fpath =

  modifyIOError (\e -> annotateIOError e descr hndl fpath)

-- | 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).

daemonize :: FilePath -> (Maybe Fd -> IO ()) -> IO ()

daemonize logfile action = do

  (rpipe, wpipe) <- createPipe

  -- first fork

  _ <- forkProcess $ do

    -- in the child

    closeFd rpipe

    setupDaemonEnv "/" (unionFileModes groupModes otherModes)

    setupDaemonFDs $ Just logfile

    _ <- installHandler lostConnection (Catch (handleSigHup logfile)) Nothing

    -- second fork, launches the actual child code; standard

    -- double-fork technique

    _ <- forkProcess (action (Just wpipe))

    exitImmediately ExitSuccess

  closeFd wpipe

  hndl <- fdToHandle rpipe

  errors <- hGetContents hndl

  ecode <- if null errors

             then return ExitSuccess

             else do

               hPutStrLn stderr $ daemonStartupErr errors

               return $ ExitFailure C.exitFailure

  exitImmediately ecode

-- | Generic daemon startup.

genericMain :: GanetiDaemon -- ^ The daemon we're running

            -> [OptType]    -- ^ The available options

            -> CheckFn a    -- ^ Check function

            -> PrepFn  a b  -- ^ Prepare function

            -> MainFn  a b  -- ^ Execution function

            -> IO ()

genericMain daemon options check_fn prep_fn exec_fn = do

  let progname = daemonName daemon

  (opts, args) <- parseArgs progname options

  exitUnless (null args) "This program doesn't take any arguments"

  unless (optNoUserChecks opts) $ do

    runtimeEnts <- getEnts

    ents <- exitIfBad "Can't find required user/groups" runtimeEnts

    verifyDaemonUser daemon ents

  syslog <- case optSyslogUsage opts of

              Nothing -> exitIfBad "Invalid cluster syslog setting" $

                         syslogUsageFromRaw C.syslogUsage

              Just v -> return v

  -- run the check function and optionally exit if it returns an exit code

  check_result <- check_fn opts

  check_result' <- case check_result of

                     Left code -> exitWith code

                     Right v -> return v

  let processFn = if optDaemonize opts

                    then daemonize (daemonLogFile daemon)

                    else \action -> action Nothing

  processFn $ innerMain daemon opts syslog check_result' prep_fn exec_fn

-- | Full prepare function.

--

-- This is executed after daemonization, and sets up both the log

-- files (a generic functionality) and the custom prepare function of

-- the daemon.

fullPrep :: GanetiDaemon  -- ^ The daemon we're running

         -> DaemonOptions -- ^ The options structure, filled from the cmdline

         -> SyslogUsage   -- ^ Syslog mode

         -> a             -- ^ Check results

         -> PrepFn a b    -- ^ Prepare function

         -> IO b

fullPrep daemon opts syslog check_result prep_fn = do

  let logfile = if optDaemonize opts

                  then Nothing

                  else Just $ daemonLogFile daemon

      pidfile = daemonPidFile daemon

      dname = daemonName daemon

  setupLogging logfile dname (optDebug opts) True False syslog

  _ <- describeError "writing PID file; already locked?"

         Nothing (Just pidfile) $ writePidFile pidfile

  logNotice $ dname ++ " daemon startup"

  prep_fn opts check_result

-- | Inner daemon function.

--

-- This is executed after daemonization.

innerMain :: GanetiDaemon  -- ^ The daemon we're running

          -> DaemonOptions -- ^ The options structure, filled from the cmdline

          -> SyslogUsage   -- ^ Syslog mode

          -> a             -- ^ Check results

          -> PrepFn a b    -- ^ Prepare function

          -> MainFn a b    -- ^ Execution function

          -> Maybe Fd      -- ^ Error reporting function

          -> IO ()

innerMain daemon opts syslog check_result prep_fn exec_fn fd = do

  prep_result <- fullPrep daemon opts syslog check_result prep_fn

                 `Control.Exception.catch` handlePrepErr fd

  -- no error reported, we should now close the fd

  maybeCloseFd fd

  exec_fn opts check_result prep_result

-- | Daemon prepare error handling function.

handlePrepErr :: Maybe Fd -> IOError -> IO a

handlePrepErr fd err = do

  let msg = show err

  case fd of

    -- explicitly writing to the fd directly, since when forking it's

    -- better (safer) than trying to convert this into a full handle

    Just fd' -> fdWrite fd' msg >> return ()

    Nothing  -> hPutStrLn stderr (daemonStartupErr msg)

  logError msg

  exitWith $ ExitFailure 1

-- | Close a file descriptor.

maybeCloseFd :: Maybe Fd -> IO ()

maybeCloseFd Nothing   = return ()

maybeCloseFd (Just fd) = closeFd fd