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{-# LANGUAGE BangPatterns #-}

{-| Implementation of the Ganeti confd server 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.Confd.Server

  ( main

  ) where

import Control.Concurrent

import Control.Monad (forever)

import qualified Data.ByteString as B

import Data.IORef

import Data.List

import qualified Data.Map as M

import qualified Network.Socket as S

import System.Posix.Files

import System.Posix.Types

import System.Time

import qualified Text.JSON as J

import System.INotify

import Ganeti.Daemon

import Ganeti.HTools.JSON

import Ganeti.HTools.Types

import Ganeti.HTools.Utils

import Ganeti.Objects

import Ganeti.Confd

import Ganeti.Config

import Ganeti.Hash

import Ganeti.Logging

import qualified Ganeti.Constants as C

-- * Types and constants definitions

-- | What we store as configuration.

type CRef = IORef (Result (ConfigData, LinkIpMap))

-- | File stat identifier.

type FStat = (EpochTime, FileID, FileOffset)

-- | Null 'FStat' value.

nullFStat :: FStat

nullFStat = (-1, -1, -1)

-- | A small type alias for readability.

type StatusAnswer = (ConfdReplyStatus, J.JSValue)

-- | Reload model data type.

data ReloadModel = ReloadNotify      -- ^ We are using notifications

                 | ReloadPoll Int    -- ^ We are using polling

                   deriving (Eq, Show)

-- | Server state data type.

data ServerState = ServerState

  { reloadModel  :: ReloadModel

  , reloadTime   :: Integer

  , reloadFStat  :: FStat

  }

-- | Maximum no-reload poll rounds before reverting to inotify.

maxIdlePollRounds :: Int

maxIdlePollRounds = 2

-- | Reload timeout in microseconds.

configReloadTimeout :: Int

configReloadTimeout = C.confdConfigReloadTimeout * 1000000

-- | Ratelimit timeout in microseconds.

configReloadRatelimit :: Int

configReloadRatelimit = C.confdConfigReloadRatelimit * 1000000

-- | Initial poll round.

initialPoll :: ReloadModel

initialPoll = ReloadPoll 0

-- | Initial server state.

initialState :: ServerState

initialState = ServerState initialPoll 0 nullFStat

-- | Reload status data type.

data ConfigReload = ConfigToDate    -- ^ No need to reload

                  | ConfigReloaded  -- ^ Configuration reloaded

                  | ConfigIOError   -- ^ Error during configuration reload

-- | Unknown entry standard response.

queryUnknownEntry :: StatusAnswer

queryUnknownEntry = (ReplyStatusError, J.showJSON ConfdErrorUnknownEntry)

{- not used yet

-- | Internal error standard response.

queryInternalError :: StatusAnswer

queryInternalError = (ReplyStatusError, J.showJSON ConfdErrorInternal)

-}

-- | Argument error standard response.

queryArgumentError :: StatusAnswer

queryArgumentError = (ReplyStatusError, J.showJSON ConfdErrorArgument)

-- | Returns the current time.

getCurrentTime :: IO Integer

getCurrentTime = do

  TOD ctime _ <- getClockTime

  return ctime

-- * Confd base functionality

-- | Returns the HMAC key.

getClusterHmac :: IO HashKey

getClusterHmac = fmap B.unpack $ B.readFile C.confdHmacKey

-- | Computes the node role.

nodeRole :: ConfigData -> String -> Result ConfdNodeRole

nodeRole cfg name =

  let cmaster = clusterMasterNode . configCluster $ cfg

      mnode = M.lookup name . configNodes $ cfg

  in case mnode of

       Nothing -> Bad "Node not found"

       Just node | cmaster == name -> Ok NodeRoleMaster

                 | nodeDrained node -> Ok NodeRoleDrained

                 | nodeOffline node -> Ok NodeRoleOffline

                 | nodeMasterCandidate node -> Ok NodeRoleCandidate

       _ -> Ok NodeRoleRegular

-- | Does an instance ip -> instance -> primary node -> primary ip

-- transformation.

getNodePipByInstanceIp :: ConfigData

                       -> LinkIpMap

                       -> String

                       -> String

                       -> StatusAnswer

getNodePipByInstanceIp cfg linkipmap link instip =

  case M.lookup instip (M.findWithDefault M.empty link linkipmap) of

    Nothing -> queryUnknownEntry

    Just instname ->

      case getInstPrimaryNode cfg instname of

        Bad _ -> queryUnknownEntry -- either instance or node not found

        Ok node -> (ReplyStatusOk, J.showJSON (nodePrimaryIp node))

-- | Builds the response to a given query.

buildResponse :: (ConfigData, LinkIpMap) -> ConfdRequest -> Result StatusAnswer

buildResponse (cfg, _) (ConfdRequest { confdRqType = ReqPing }) =

  return (ReplyStatusOk, J.showJSON (configVersion cfg))

buildResponse cdata req@(ConfdRequest { confdRqType = ReqClusterMaster }) =

  case confdRqQuery req of

    EmptyQuery -> return (ReplyStatusOk, J.showJSON master_name)

    PlainQuery _ -> return queryArgumentError

    DictQuery reqq -> do

      mnode <- getNode cfg master_name

      let fvals =map (\field -> case field of

                                  ReqFieldName -> master_name

                                  ReqFieldIp -> clusterMasterIp cluster

                                  ReqFieldMNodePip -> nodePrimaryIp mnode

                     ) (confdReqQFields reqq)

      return (ReplyStatusOk, J.showJSON fvals)

    where master_name = clusterMasterNode cluster

          cluster = configCluster cfg

          cfg = fst cdata

buildResponse cdata req@(ConfdRequest { confdRqType = ReqNodeRoleByName }) = do

  node_name <- case confdRqQuery req of

                 PlainQuery str -> return str

                 _ -> fail $ "Invalid query type " ++ show (confdRqQuery req)

  role <- nodeRole (fst cdata) node_name

  return (ReplyStatusOk, J.showJSON role)

buildResponse cdata (ConfdRequest { confdRqType = ReqNodePipList }) =

  -- note: we use foldlWithKey because that's present accross more

  -- versions of the library

  return (ReplyStatusOk, J.showJSON $

          M.foldlWithKey (\accu _ n -> nodePrimaryIp n:accu) []

          (configNodes (fst cdata)))

buildResponse cdata (ConfdRequest { confdRqType = ReqMcPipList }) =

  -- note: we use foldlWithKey because that's present accross more

  -- versions of the library

  return (ReplyStatusOk, J.showJSON $

          M.foldlWithKey (\accu _ n -> if nodeMasterCandidate n

                                         then nodePrimaryIp n:accu

                                         else accu) []

          (configNodes (fst cdata)))

buildResponse (cfg, linkipmap)

              req@(ConfdRequest { confdRqType = ReqInstIpsList }) = do

  link <- case confdRqQuery req of

            PlainQuery str -> return str

            EmptyQuery -> return (getDefaultNicLink cfg)

            _ -> fail "Invalid query type"

  return (ReplyStatusOk, J.showJSON $ getInstancesIpByLink linkipmap link)

buildResponse cdata (ConfdRequest { confdRqType = ReqNodePipByInstPip

                                  , confdRqQuery = DictQuery query}) =

  let (cfg, linkipmap) = cdata

      link = maybe (getDefaultNicLink cfg) id (confdReqQLink query)

  in case confdReqQIp query of

       Just ip -> return $ getNodePipByInstanceIp cfg linkipmap link ip

       Nothing -> return (ReplyStatusOk,

                          J.showJSON $

                           map (getNodePipByInstanceIp cfg linkipmap link)

                           (confdReqQIpList query))

buildResponse _ (ConfdRequest { confdRqType = ReqNodePipByInstPip }) =

  return queryArgumentError

-- | Parses a signed request.

parseRequest :: HashKey -> String -> Result (String, String, ConfdRequest)

parseRequest key str = do

  (SignedMessage hmac msg salt) <- fromJResult "parsing request" $ J.decode str

  req <- if verifyMac key (Just salt) msg hmac

           then fromJResult "parsing message" $ J.decode msg

           else Bad "HMAC verification failed"

  return (salt, msg, req)

-- | Creates a ConfdReply from a given answer.

serializeResponse :: Result StatusAnswer -> ConfdReply

serializeResponse r =

    let (status, result) = case r of

                    Bad err -> (ReplyStatusError, J.showJSON err)

                    Ok (code, val) -> (code, val)

    in ConfdReply { confdReplyProtocol = 1

                  , confdReplyStatus   = status

                  , confdReplyAnswer   = result

                  , confdReplySerial   = 0 }

-- | Signs a message with a given key and salt.

signMessage :: HashKey -> String -> String -> SignedMessage

signMessage key salt msg =

  SignedMessage { signedMsgMsg  = msg

                , signedMsgSalt = salt

                , signedMsgHmac = hmac

                }

    where hmac = computeMac key (Just salt) msg

-- * Configuration handling

-- ** Helper functions

-- | Helper function for logging transition into polling mode.

moveToPolling :: String -> INotify -> FilePath -> CRef -> MVar ServerState

              -> IO ReloadModel

moveToPolling msg inotify path cref mstate = do

  logInfo $ "Moving to polling mode: " ++ msg

  let inotiaction = addNotifier inotify path cref mstate

  _ <- forkIO $ onReloadTimer inotiaction path cref mstate

  return initialPoll

-- | Helper function for logging transition into inotify mode.

moveToNotify :: IO ReloadModel

moveToNotify = do

  logInfo "Moving to inotify mode"

  return ReloadNotify

-- ** Configuration loading

-- | (Re)loads the configuration.

updateConfig :: FilePath -> CRef -> IO ()

updateConfig path r = do

  newcfg <- loadConfig path

  let !newdata = case newcfg of

                   Ok !cfg -> Ok (cfg, buildLinkIpInstnameMap cfg)

                   Bad _ -> Bad "Cannot load configuration"

  writeIORef r newdata

  case newcfg of

    Ok cfg -> logInfo ("Loaded new config, serial " ++

                       show (configSerial cfg))

    Bad msg -> logError $ "Failed to load config: " ++ msg

  return ()

-- | Wrapper over 'updateConfig' that handles IO errors.

safeUpdateConfig :: FilePath -> FStat -> CRef -> IO (FStat, ConfigReload)

safeUpdateConfig path oldfstat cref = do

  catch (do

          nt <- needsReload oldfstat path

          case nt of

            Nothing -> return (oldfstat, ConfigToDate)

            Just nt' -> do

                    updateConfig path cref

                    return (nt', ConfigReloaded)

        ) (\e -> do

             let msg = "Failure during configuration update: " ++ show e

             writeIORef cref (Bad msg)

             return (nullFStat, ConfigIOError)

          )

-- | Computes the file cache data from a FileStatus structure.

buildFileStatus :: FileStatus -> FStat

buildFileStatus ofs =

    let modt = modificationTime ofs

        inum = fileID ofs

        fsize = fileSize ofs

    in (modt, inum, fsize)

-- | Wrapper over 'buildFileStatus'. This reads the data from the

-- filesystem and then builds our cache structure.

getFStat :: FilePath -> IO FStat

getFStat p = getFileStatus p >>= (return . buildFileStatus)

-- | Check if the file needs reloading

needsReload :: FStat -> FilePath -> IO (Maybe FStat)

needsReload oldstat path = do

  newstat <- getFStat path

  return $ if newstat /= oldstat

             then Just newstat

             else Nothing

-- ** Watcher threads

-- $watcher

-- We have three threads/functions that can mutate the server state:

--

-- 1. the long-interval watcher ('onTimeoutTimer')

--

-- 2. the polling watcher ('onReloadTimer')

--

-- 3. the inotify event handler ('onInotify')

--

-- All of these will mutate the server state under 'modifyMVar' or

-- 'modifyMVar_', so that server transitions are more or less

-- atomic. The inotify handler remains active during polling mode, but

-- checks for polling mode and doesn't do anything in this case (this

-- check is needed even if we would unregister the event handler due

-- to how events are serialised).

-- | Long-interval reload watcher.

--

-- This is on top of the inotify-based triggered reload.

onTimeoutTimer :: IO Bool -> FilePath -> CRef -> MVar ServerState -> IO ()

onTimeoutTimer inotiaction path cref state = do

  threadDelay configReloadTimeout

  modifyMVar_ state (onTimeoutInner path cref)

  _ <- inotiaction

  onTimeoutTimer inotiaction path cref state

-- | Inner onTimeout handler.

--

-- This mutates the server state under a modifyMVar_ call. It never

-- changes the reload model, just does a safety reload and tried to

-- re-establish the inotify watcher.

onTimeoutInner :: FilePath -> CRef -> ServerState -> IO ServerState

onTimeoutInner path cref state  = do

  (newfstat, _) <- safeUpdateConfig path (reloadFStat state) cref

  return state { reloadFStat = newfstat }

-- | Short-interval (polling) reload watcher.

--

-- This is only active when we're in polling mode; it will

-- automatically exit when it detects that the state has changed to

-- notification.

onReloadTimer :: IO Bool -> FilePath -> CRef -> MVar ServerState -> IO ()

onReloadTimer inotiaction path cref state = do

  continue <- modifyMVar state (onReloadInner inotiaction path cref)

  if continue

    then do

      threadDelay configReloadRatelimit

      onReloadTimer inotiaction path cref state

    else -- the inotify watch has been re-established, we can exit

      return ()

-- | Inner onReload handler.

--

-- This again mutates the state under a modifyMVar call, and also

-- returns whether the thread should continue or not.

onReloadInner :: IO Bool -> FilePath -> CRef -> ServerState

              -> IO (ServerState, Bool)

onReloadInner _ _ _ state@(ServerState { reloadModel = ReloadNotify } ) =

  return (state, False)

onReloadInner inotiaction path cref

              state@(ServerState { reloadModel = ReloadPoll pround } ) = do

  (newfstat, reload) <- safeUpdateConfig path (reloadFStat state) cref

  let state' = state { reloadFStat = newfstat }

  -- compute new poll model based on reload data; however, failure to

  -- re-establish the inotifier means we stay on polling

  newmode <- case reload of

               ConfigToDate ->

                 if pround >= maxIdlePollRounds

                   then do -- try to switch to notify

                     result <- inotiaction

                     if result

                       then moveToNotify

                       else return initialPoll

                   else return (ReloadPoll (pround + 1))

               _ -> return initialPoll

  let continue = case newmode of

                   ReloadNotify -> False

                   _            -> True

  return (state' { reloadModel = newmode }, continue)

-- | Setup inotify watcher.

--

-- This tries to setup the watch descriptor; in case of any IO errors,

-- it will return False.

addNotifier :: INotify -> FilePath -> CRef -> MVar ServerState -> IO Bool

addNotifier inotify path cref mstate = do

  catch (addWatch inotify [CloseWrite] path

                    (onInotify inotify path cref mstate) >> return True)

        (const $ return False)

-- | Inotify event handler.

onInotify :: INotify -> String -> CRef -> MVar ServerState -> Event -> IO ()

onInotify inotify path cref mstate Ignored = do

  logInfo "File lost, trying to re-establish notifier"

  modifyMVar_ mstate $ \state -> do

    result <- addNotifier inotify path cref mstate

    (newfstat, _) <- safeUpdateConfig path (reloadFStat state) cref

    let state' = state { reloadFStat = newfstat }

    if result

      then return state' -- keep notify

      else do

        mode <- moveToPolling "cannot re-establish inotify watch" inotify

                  path cref mstate

        return state' { reloadModel = mode }

onInotify inotify path cref mstate _ = do

  modifyMVar_ mstate $ \state ->

    if (reloadModel state == ReloadNotify)

       then do

         ctime <- getCurrentTime

         (newfstat, _) <- safeUpdateConfig path (reloadFStat state) cref

         let state' = state { reloadFStat = newfstat, reloadTime = ctime }

         if abs (reloadTime state - ctime) <

            fromIntegral C.confdConfigReloadRatelimit

           then do

             mode <- moveToPolling "too many reloads" inotify path cref mstate

             return state' { reloadModel = mode }

           else return state'

      else return state

-- ** Client input/output handlers

-- | Main loop for a given client.

responder :: CRef -> S.Socket -> HashKey -> String -> S.SockAddr -> IO ()

responder cfgref socket hmac msg peer = do

  ctime <- getCurrentTime

  case parseMessage hmac msg ctime of

    Ok (origmsg, rq) -> do

              logDebug $ "Processing request: " ++ origmsg

              mcfg <- readIORef cfgref

              let response = respondInner mcfg hmac rq

              _ <- S.sendTo socket response peer

              return ()

    Bad err -> logInfo $ "Failed to parse incoming message: " ++ err

  return ()

-- | Mesage parsing. This can either result in a good, valid message,

-- or fail in the Result monad.

parseMessage :: HashKey -> String -> Integer

             -> Result (String, ConfdRequest)

parseMessage hmac msg curtime = do

  (salt, origmsg, request) <- parseRequest hmac msg

  ts <- tryRead "Parsing timestamp" salt::Result Integer

  if (abs (ts - curtime) > (fromIntegral C.confdMaxClockSkew))

    then fail "Too old/too new timestamp or clock skew"

    else return (origmsg, request)

-- | Inner helper function for a given client. This generates the

-- final encoded message (as a string), ready to be sent out to the

-- client.

respondInner :: Result (ConfigData, LinkIpMap) -> HashKey

             -> ConfdRequest -> String

respondInner cfg hmac rq =

  let rsalt = confdRqRsalt rq

      innermsg = serializeResponse (cfg >>= flip buildResponse rq)

      innerserialised = J.encodeStrict innermsg

      outermsg = signMessage hmac rsalt innerserialised

      outerserialised = confdMagicFourcc ++ J.encodeStrict outermsg

  in outerserialised

-- | Main listener loop.

listener :: S.Socket -> HashKey

         -> (S.Socket -> HashKey -> String -> S.SockAddr -> IO ())

         -> IO ()

listener s hmac resp = do

  (msg, _, peer) <- S.recvFrom s 4096

  if confdMagicFourcc `isPrefixOf` msg

    then (forkIO $ resp s hmac (drop 4 msg) peer) >> return ()

    else logDebug "Invalid magic code!" >> return ()

  return ()

-- | Main function.

main :: DaemonOptions -> IO ()

main opts = do

  parseresult <- parseAddress opts C.defaultConfdPort

  (af_family, bindaddr) <- exitIfBad "parsing bind address" parseresult

  s <- S.socket af_family S.Datagram S.defaultProtocol

  S.bindSocket s bindaddr

  cref <- newIORef (Bad "Configuration not yet loaded")

  statemvar <- newMVar initialState

  hmac <- getClusterHmac

  -- Inotify setup

  inotify <- initINotify

  let inotiaction = addNotifier inotify C.clusterConfFile cref statemvar

  -- fork the timeout timer

  _ <- forkIO $ onTimeoutTimer inotiaction C.clusterConfFile cref statemvar

  -- fork the polling timer

  _ <- forkIO $ onReloadTimer inotiaction C.clusterConfFile cref statemvar

  -- and finally enter the responder loop

  forever $ listener s hmac (responder cref)