232 lines
11 KiB
Haskell
232 lines
11 KiB
Haskell
-- | Connect to a single server or a replica set of servers
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{-# LANGUAGE CPP, OverloadedStrings, ScopedTypeVariables, TupleSections #-}
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#if (__GLASGOW_HASKELL__ >= 706)
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{-# LANGUAGE RecursiveDo #-}
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#else
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{-# LANGUAGE DoRec #-}
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#endif
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module Database.MongoDB.Connection (
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-- * Util
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Secs,
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-- * Connection
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Pipe, close, isClosed,
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-- * Server
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Host(..), PortID(..), defaultPort, host, showHostPort, readHostPort,
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readHostPortM, globalConnectTimeout, connect, connect',
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-- * Replica Set
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ReplicaSetName, openReplicaSet, openReplicaSet',
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ReplicaSet, primary, secondaryOk, routedHost, closeReplicaSet, replSetName
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) where
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import Prelude hiding (lookup)
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import Data.IORef (IORef, newIORef, readIORef)
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import Data.List (intersect, partition, (\\), delete)
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#if !MIN_VERSION_base(4,8,0)
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import Control.Applicative ((<$>))
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#endif
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import Control.Monad (forM_, guard)
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import System.IO.Unsafe (unsafePerformIO)
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import System.Timeout (timeout)
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import Text.ParserCombinators.Parsec (parse, many1, letter, digit, char, anyChar, eof,
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spaces, try, (<|>))
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import qualified Data.List as List
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import Control.Monad.Identity (runIdentity)
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import Control.Monad.Except (throwError)
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import Control.Concurrent.MVar.Lifted (MVar, newMVar, withMVar, modifyMVar,
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readMVar)
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import Data.Bson (Document, at, (=:))
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import Data.Text (Text)
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import qualified Data.Bson as B
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import qualified Data.Text as T
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import Database.MongoDB.Internal.Network (HostName, PortID(..), connectTo)
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import Database.MongoDB.Internal.Protocol (Pipe, newPipe, close, isClosed)
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import Database.MongoDB.Internal.Util (untilSuccess, liftIOE,
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updateAssocs, shuffle, mergesortM)
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import Database.MongoDB.Query (Command, Failure(ConnectionFailure), access,
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slaveOk, runCommand, retrieveServerData)
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adminCommand :: Command -> Pipe -> IO Document
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-- ^ Run command against admin database on server connected to pipe. Fail if connection fails.
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adminCommand cmd pipe =
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liftIOE failureToIOError $ access pipe slaveOk "admin" $ runCommand cmd
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where
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failureToIOError (ConnectionFailure e) = e
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failureToIOError e = userError $ show e
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-- * Host
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data Host = Host HostName PortID deriving (Show, Eq, Ord)
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defaultPort :: PortID
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-- ^ Default MongoDB port = 27017
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defaultPort = PortNumber 27017
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host :: HostName -> Host
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-- ^ Host on 'defaultPort'
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host hostname = Host hostname defaultPort
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showHostPort :: Host -> String
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-- ^ Display host as \"host:port\"
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-- TODO: Distinguish Service port
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showHostPort (Host hostname (PortNumber port)) = hostname ++ ":" ++ show port
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#if !defined(mingw32_HOST_OS) && !defined(cygwin32_HOST_OS) && !defined(_WIN32)
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showHostPort (Host _ (UnixSocket path)) = "unix:" ++ path
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#endif
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readHostPortM :: (Monad m) => String -> m Host
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-- ^ Read string \"hostname:port\" as @Host hosthame (PortNumber port)@ or \"hostname\" as @host hostname@ (default port). Fail if string does not match either syntax.
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-- TODO: handle Service port
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readHostPortM = either (fail . show) return . parse parser "readHostPort" where
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hostname = many1 (letter <|> digit <|> char '-' <|> char '.')
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parser = do
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spaces
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h <- hostname
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try (spaces >> eof >> return (host h)) <|> do
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_ <- char ':'
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try ( do port :: Int <- read <$> many1 digit
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spaces >> eof
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return $ Host h (PortNumber $ fromIntegral port))
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#if !defined(mingw32_HOST_OS) && !defined(cygwin32_HOST_OS) && !defined(_WIN32)
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<|> do guard (h == "unix")
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p <- many1 anyChar
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eof
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return $ Host "" (UnixSocket p)
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#endif
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readHostPort :: String -> Host
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-- ^ Read string \"hostname:port\" as @Host hostname (PortNumber port)@ or \"hostname\" as @host hostname@ (default port). Error if string does not match either syntax.
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readHostPort = runIdentity . readHostPortM
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type Secs = Double
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globalConnectTimeout :: IORef Secs
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-- ^ 'connect' (and 'openReplicaSet') fails if it can't connect within this many seconds (default is 6 seconds). Use 'connect\'' (and 'openReplicaSet\'') if you want to ignore this global and specify your own timeout. Note, this timeout only applies to initial connection establishment, not when reading/writing to the connection.
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globalConnectTimeout = unsafePerformIO (newIORef 6)
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{-# NOINLINE globalConnectTimeout #-}
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connect :: Host -> IO Pipe
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-- ^ Connect to Host returning pipelined TCP connection. Throw IOError if connection refused or no response within 'globalConnectTimeout'.
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connect h = readIORef globalConnectTimeout >>= flip connect' h
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connect' :: Secs -> Host -> IO Pipe
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-- ^ Connect to Host returning pipelined TCP connection. Throw IOError if connection refused or no response within given number of seconds.
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connect' timeoutSecs (Host hostname port) = do
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mh <- timeout (round $ timeoutSecs * 1000000) (connectTo hostname port)
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handle <- maybe (ioError $ userError "connect timed out") return mh
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rec
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p <- newPipe sd handle
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sd <- access p slaveOk "admin" retrieveServerData
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return p
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-- * Replica Set
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type ReplicaSetName = Text
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-- | Maintains a connection (created on demand) to each server in the named replica set
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data ReplicaSet = ReplicaSet ReplicaSetName (MVar [(Host, Maybe Pipe)]) Secs
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replSetName :: ReplicaSet -> Text
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-- ^ name of connected replica set
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replSetName (ReplicaSet rsName _ _) = rsName
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openReplicaSet :: (ReplicaSetName, [Host]) -> IO ReplicaSet
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-- ^ Open connections (on demand) to servers in replica set. Supplied hosts is seed list. At least one of them must be a live member of the named replica set, otherwise fail. The value of 'globalConnectTimeout' at the time of this call is the timeout used for future member connect attempts. To use your own value call 'openReplicaSet\'' instead.
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openReplicaSet rsSeed = readIORef globalConnectTimeout >>= flip openReplicaSet' rsSeed
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openReplicaSet' :: Secs -> (ReplicaSetName, [Host]) -> IO ReplicaSet
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-- ^ Open connections (on demand) to servers in replica set. Supplied hosts is seed list. At least one of them must be a live member of the named replica set, otherwise fail. Supplied seconds timeout is used for connect attempts to members.
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openReplicaSet' timeoutSecs (rsName, seedList) = do
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vMembers <- newMVar (map (, Nothing) seedList)
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let rs = ReplicaSet rsName vMembers timeoutSecs
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_ <- updateMembers rs
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return rs
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closeReplicaSet :: ReplicaSet -> IO ()
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-- ^ Close all connections to replica set
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closeReplicaSet (ReplicaSet _ vMembers _) = withMVar vMembers $ mapM_ (maybe (return ()) close . snd)
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primary :: ReplicaSet -> IO Pipe
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-- ^ Return connection to current primary of replica set. Fail if no primary available.
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primary rs@(ReplicaSet rsName _ _) = do
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mHost <- statedPrimary <$> updateMembers rs
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case mHost of
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Just host' -> connection rs Nothing host'
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Nothing -> throwError $ userError $ "replica set " ++ T.unpack rsName ++ " has no primary"
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secondaryOk :: ReplicaSet -> IO Pipe
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-- ^ Return connection to a random secondary, or primary if no secondaries available.
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secondaryOk rs = do
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info <- updateMembers rs
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hosts <- shuffle (possibleHosts info)
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let hosts' = maybe hosts (\p -> delete p hosts ++ [p]) (statedPrimary info)
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untilSuccess (connection rs Nothing) hosts'
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routedHost :: ((Host, Bool) -> (Host, Bool) -> IO Ordering) -> ReplicaSet -> IO Pipe
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-- ^ Return a connection to a host using a user-supplied sorting function, which sorts based on a tuple containing the host and a boolean indicating whether the host is primary.
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routedHost f rs = do
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info <- updateMembers rs
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hosts <- shuffle (possibleHosts info)
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let addIsPrimary h = (h, if Just h == statedPrimary info then True else False)
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hosts' <- mergesortM (\a b -> f (addIsPrimary a) (addIsPrimary b)) hosts
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untilSuccess (connection rs Nothing) hosts'
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type ReplicaInfo = (Host, Document)
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-- ^ Result of isMaster command on host in replica set. Returned fields are: setName, ismaster, secondary, hosts, [primary]. primary only present when ismaster = false
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statedPrimary :: ReplicaInfo -> Maybe Host
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-- ^ Primary of replica set or Nothing if there isn't one
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statedPrimary (host', info) = if (at "ismaster" info) then Just host' else readHostPort <$> B.lookup "primary" info
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possibleHosts :: ReplicaInfo -> [Host]
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-- ^ Non-arbiter, non-hidden members of replica set
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possibleHosts (_, info) = map readHostPort $ at "hosts" info
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updateMembers :: ReplicaSet -> IO ReplicaInfo
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-- ^ Fetch replica info from any server and update members accordingly
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updateMembers rs@(ReplicaSet _ vMembers _) = do
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(host', info) <- untilSuccess (fetchReplicaInfo rs) =<< readMVar vMembers
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modifyMVar vMembers $ \members -> do
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let ((members', old), new) = intersection (map readHostPort $ at "hosts" info) members
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forM_ old $ \(_, mPipe) -> maybe (return ()) close mPipe
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return (members' ++ map (, Nothing) new, (host', info))
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where
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intersection :: (Eq k) => [k] -> [(k, v)] -> (([(k, v)], [(k, v)]), [k])
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intersection keys assocs = (partition (flip elem inKeys . fst) assocs, keys \\ inKeys) where
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assocKeys = map fst assocs
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inKeys = intersect keys assocKeys
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fetchReplicaInfo :: ReplicaSet -> (Host, Maybe Pipe) -> IO ReplicaInfo
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-- Connect to host and fetch replica info from host creating new connection if missing or closed (previously failed). Fail if not member of named replica set.
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fetchReplicaInfo rs@(ReplicaSet rsName _ _) (host', mPipe) = do
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pipe <- connection rs mPipe host'
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info <- adminCommand ["isMaster" =: (1 :: Int)] pipe
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case B.lookup "setName" info of
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Nothing -> throwError $ userError $ show host' ++ " not a member of any replica set, including " ++ T.unpack rsName ++ ": " ++ show info
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Just setName | setName /= rsName -> throwError $ userError $ show host' ++ " not a member of replica set " ++ T.unpack rsName ++ ": " ++ show info
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Just _ -> return (host', info)
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connection :: ReplicaSet -> Maybe Pipe -> Host -> IO Pipe
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-- ^ Return new or existing connection to member of replica set. If pipe is already known for host it is given, but we still test if it is open.
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connection (ReplicaSet _ vMembers timeoutSecs) mPipe host' =
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maybe conn (\p -> isClosed p >>= \bad -> if bad then conn else return p) mPipe
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where
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conn = modifyMVar vMembers $ \members -> do
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let new = connect' timeoutSecs host' >>= \pipe -> return (updateAssocs host' (Just pipe) members, pipe)
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case List.lookup host' members of
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Just (Just pipe) -> isClosed pipe >>= \bad -> if bad then new else return (members, pipe)
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_ -> new
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{- Authors: Tony Hannan <tony@10gen.com>
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Copyright 2011 10gen Inc.
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Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0. Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. -}
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