mongodb/Database/MongoDB/Connection.hs

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{- | A pool of TCP connections to a single server or a replica set of servers. -}
{-# LANGUAGE OverloadedStrings, ScopedTypeVariables, RecordWildCards, NamedFieldPuns, MultiParamTypeClasses, FlexibleContexts, TypeFamilies, DoRec, RankNTypes, FlexibleInstances #-}
module Database.MongoDB.Connection (
-- * Network
Network', ANetwork', Internet(..),
-- * Host
Host(..), PortID(..), host, showHostPort, readHostPort, readHostPortM,
-- * ReplicaSet
ReplicaSet(..), Name,
-- * MasterOrSlaveOk
MasterOrSlaveOk(..),
-- * Connection Pool
Server(..), newConnPool',
connHost, replicaSet
) where
import Database.MongoDB.Internal.Protocol as X
import Network.Abstract (IOE, connect, ANetwork(..))
import Data.Bson ((=:), at, UString)
import Control.Pipeline as P
import Control.Applicative ((<$>))
import Control.Exception (assert)
import Control.Monad.Error
import Control.Monad.MVar
import Control.Monad.Context
import Network (HostName, PortID(..))
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import Data.Bson (Document, look)
import Text.ParserCombinators.Parsec as T (parse, many1, letter, digit, char, eof, spaces, try, (<|>))
import Control.Monad.Identity
import Control.Monad.Util (MonadIO', untilSuccess)
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import Database.MongoDB.Internal.Util () -- PortID instances
import Var.Pool
import System.Random (newStdGen, randomRs)
import Data.List (delete, find, nub)
import System.IO.Unsafe (unsafePerformIO)
type Name = UString
adminCommand :: Document -> Request
-- ^ Convert command to request
adminCommand cmd = Query{..} where
qOptions = [SlaveOK]
qFullCollection = "admin.$cmd"
qSkip = 0
qBatchSize = 0
qSelector = cmd
qProjector = []
commandReply :: String -> Reply -> Document
-- ^ Extract first document from reply. Error if query error, using given string as prefix error message.
commandReply title Reply{..} = if elem QueryError rResponseFlags
then error $ title ++ ": " ++ at "$err" (head rDocuments)
else head rDocuments
-- * Host
data Host = Host HostName PortID deriving (Show, Eq, Ord)
defaultPort :: PortID
defaultPort = PortNumber 27017
host :: HostName -> Host
-- ^ Host on default MongoDB port
host hostname = Host hostname defaultPort
showHostPort :: Host -> String
-- ^ Display host as \"host:port\"
showHostPort (Host hostname port) = hostname ++ ":" ++ (case port of
Service s -> s
PortNumber p -> show p
UnixSocket s -> s)
readHostPortM :: (Monad m) => String -> m Host
-- ^ Read string \"hostname:port\" as @Host hosthame port@ or \"hostname\" as @host hostname@ (default port). Fail if string does not match either syntax.
readHostPortM = either (fail . show) return . parse parser "readHostPort" where
hostname = many1 (letter <|> digit <|> char '-' <|> char '.')
parser = do
spaces
h <- hostname
T.try (spaces >> eof >> return (host h)) <|> do
_ <- char ':'
port :: Int <- read <$> many1 digit
spaces >> eof
return $ Host h (PortNumber $ fromIntegral port)
readHostPort :: String -> Host
-- ^ Read string \"hostname:port\" as @Host hostname port@ or \"hostname\" as @host hostname@ (default port). Error if string does not match either syntax.
readHostPort = runIdentity . readHostPortM
-- * Replica Set
data ReplicaSet = ReplicaSet {setName :: Name, seedHosts :: [Host]} deriving (Show)
-- ^ Replica set of hosts identified by set name. At least one of the seed hosts must be an active member of the set. However, this list is not used to identify the set, just the set name.
instance Eq ReplicaSet where ReplicaSet x _ == ReplicaSet y _ = x == y
-- ** Replica Info
getReplicaInfo :: Pipe -> IOE ReplicaInfo
-- ^ Get replica info of the connected host. Throw IOError if connection fails or host is not part of a replica set (no /hosts/ and /primary/ field).
getReplicaInfo pipe = do
promise <- X.call pipe [] (adminCommand ["ismaster" =: (1 :: Int)])
info <- commandReply "ismaster" <$> promise
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_ <- look "hosts" info
_ <- look "primary" info
return info
type ReplicaInfo = Document
-- ^ Configuration info of a host in a replica set (result of /ismaster/ command). Contains all the hosts in the replica set plus its role in that set (master, slave, or arbiter)
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{- isPrimary :: ReplicaInfo -> Bool
-- ^ Is the replica described by this info a master/primary (not slave or arbiter)?
isPrimary = true1 "ismaster"
isSecondary :: ReplicaInfo -> Bool
-- ^ Is the replica described by this info a slave/secondary (not master or arbiter)
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isSecondary = true1 "secondary" -}
replicas :: ReplicaInfo -> [Host]
-- ^ All replicas in set according to this replica configuration info.
replicas = map readHostPort . at "hosts"
primary :: ReplicaInfo -> Host
-- ^ Read primary from configuration info
primary = readHostPort . at "primary"
hosts :: ReplicaInfo -> [Host]
-- ^ replicas with primary at head
hosts info = master : delete master members where
members = replicas info
master = primary info
-- * MasterOrSlaveOk
data MasterOrSlaveOk =
Master -- ^ connect to master only
| SlaveOk -- ^ connect to a slave, or master if no slave available
deriving (Show, Eq)
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{- isMS :: MasterOrSlaveOk -> ReplicaInfo -> Bool
-- ^ Does the host (as described by its replica-info) match the master/slave type
isMS Master i = isPrimary i
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isMS SlaveOk i = isSecondary i || isPrimary i -}
-- * Connection Pool
type Pool' = Pool IOError
-- | A Server is a single server ('Host') or a replica set of servers ('ReplicaSet')
class Server t where
data ConnPool t
-- ^ A pool of TCP connections ('Pipe's) to a host or a replica set of hosts
newConnPool :: (Network' n, MonadIO' m) => n -> Int -> t -> m (ConnPool t)
-- ^ Create a ConnectionPool to a host or a replica set of hosts. Actual TCP connection is not attempted until 'getPipe' request, so no IOError can be raised here. Up to N TCP connections will be established to each host.
getPipe :: MasterOrSlaveOk -> ConnPool t -> IOE Pipe
-- ^ Return a TCP connection (Pipe) to the master or a slave in the server. Master must connect to the master, SlaveOk may connect to a slave or master. To spread the load, SlaveOk requests are distributed amongst all hosts in the server. Throw IOError if failed to connect to right type of host (Master/SlaveOk).
killPipes :: ConnPool t -> IO ()
-- ^ Kill all open pipes (TCP Connections). Will cause any users of them to fail. Alternatively you can let them die on their own when they get garbage collected.
newConnPool' :: (Server t, MonadIO' m, Context ANetwork' m) => Int -> t -> m (ConnPool t)
newConnPool' poolSize' host' = context >>= \(ANetwork net :: ANetwork') -> newConnPool net poolSize' host'
-- ** ConnectionPool Host
instance Server Host where
data ConnPool Host = HostConnPool {connHost :: Host, connPool :: Pool' Pipe}
-- ^ A pool of TCP connections ('Pipe's) to a server, handed out in round-robin style.
newConnPool net poolSize' host' = liftIO $ newHostConnPool (ANetwork net) poolSize' host'
-- ^ Create a connection pool to server (host or replica set)
getPipe _ = getHostPipe
-- ^ Return a TCP connection (Pipe). If SlaveOk, connect to a slave if available. Round-robin if multiple slaves are available. Throw IOError if failed to connect.
killPipes (HostConnPool _ pool) = killAll pool
instance Show (ConnPool Host) where
show HostConnPool{connHost} = "ConnPool " ++ show connHost
newHostConnPool :: ANetwork' -> Int -> Host -> IO (ConnPool Host)
-- ^ Create a pool of N 'Pipe's (TCP connections) to server. 'getHostPipe' will return one of those pipes, round-robin style.
newHostConnPool net poolSize' host' = HostConnPool host' <$> newPool Factory{..} poolSize' where
newResource = tcpConnect net host'
killResource = P.close
isExpired = P.isClosed
getHostPipe :: ConnPool Host -> IOE Pipe
-- ^ Return next pipe (TCP connection) in connection pool, round-robin style. Throw IOError if can't connect to host.
getHostPipe (HostConnPool _ pool) = aResource pool
tcpConnect :: ANetwork' -> Host -> IOE Pipe
-- ^ Create a TCP connection (Pipe) to the given host. Throw IOError if can't connect.
tcpConnect net (Host hostname port) = newPipeline =<< connect net (hostname, port)
-- ** Connection ReplicaSet
instance Server ReplicaSet where
data ConnPool ReplicaSet = ReplicaSetConnPool {
network :: ANetwork',
repsetName :: Name,
currentMembers :: MVar [ConnPool Host] } -- master at head after a refresh
newConnPool net poolSize' repset = liftIO $ newSetConnPool (ANetwork net) poolSize' repset
getPipe = getSetPipe
killPipes ReplicaSetConnPool{..} = withMVar currentMembers (mapM_ killPipes)
instance Show (ConnPool ReplicaSet) where
show r = "ConnPool " ++ show (unsafePerformIO $ replicaSet r)
replicaSet :: (MonadIO' m) => ConnPool ReplicaSet -> m ReplicaSet
-- ^ Return replicas set name with current members as seed list
replicaSet ReplicaSetConnPool{..} = ReplicaSet repsetName . map connHost <$> readMVar currentMembers
newSetConnPool :: ANetwork' -> Int -> ReplicaSet -> IO (ConnPool ReplicaSet)
-- ^ Create a connection pool to each member of the replica set.
newSetConnPool net poolSize' repset = assert (not . null $ seedHosts repset) $ do
currentMembers <- newMVar =<< mapM (newHostConnPool net poolSize') (seedHosts repset)
return $ ReplicaSetConnPool net (setName repset) currentMembers
getMembers :: Name -> [ConnPool Host] -> IOE [Host]
-- ^ Get members of replica set, master first. Query supplied connections until config found.
-- TODO: Verify config for request replica set name and not some other replica set. ismaster config should include replica set name in result but currently does not.
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getMembers _repsetName connections = hosts <$> untilSuccess (getReplicaInfo <=< getHostPipe) connections
refreshMembers :: ANetwork' -> Name -> [ConnPool Host] -> IOE [ConnPool Host]
-- ^ Update current members with master at head. Reuse unchanged members. Throw IOError if can't connect to any and fetch config. Dropped connections are not closed in case they still have users; they will be closed when garbage collected.
refreshMembers net repsetName connections = do
n <- liftIO . poolSize . connPool $ head connections
mapM (liftIO . connection n) =<< getMembers repsetName connections
where
connection n host' = maybe (newHostConnPool net n host') return mc where
mc = find ((host' ==) . connHost) connections
getSetPipe :: MasterOrSlaveOk -> ConnPool ReplicaSet -> IOE Pipe
-- ^ Return a pipe to primary or a random secondary in replica set. Use primary for SlaveOk if and only if no secondaries. Note, refreshes members each time (makes ismaster call to primary).
getSetPipe mos ReplicaSetConnPool{..} = modifyMVar currentMembers $ \conns -> do
connections <- refreshMembers network repsetName conns -- master at head after refresh
pipe <- case mos of
Master -> getHostPipe (head connections)
SlaveOk -> do
let n = length connections - 1
is <- take (max 1 n) . nub . randomRs (min 1 n, n) <$> liftIO newStdGen
untilSuccess (getHostPipe . (connections !!)) is
return (connections, pipe)
{- Authors: Tony Hannan <tony@10gen.com>
Copyright 2010 10gen Inc.
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. -}