Retrieve server data on connection

Database/MongoDB/Connection.hs

@@ -2,6 +2,12 @@
 
 {-# LANGUAGE CPP, OverloadedStrings, ScopedTypeVariables, TupleSections #-}
 
+#if (__GLASGOW_HASKELL__ >= 706)
+{-# LANGUAGE RecursiveDo #-}
+#else
+{-# LANGUAGE DoRec #-}
+#endif
+
 module Database.MongoDB.Connection (
     -- * Util
     Secs,
@@ -46,7 +52,7 @@ import Database.MongoDB.Internal.Protocol (Pipe, newPipe, close, isClosed)
 import Database.MongoDB.Internal.Util (untilSuccess, liftIOE,
                                        updateAssocs, shuffle, mergesortM)
 import Database.MongoDB.Query (Command, Failure(ConnectionFailure), access,
-                              slaveOk, runCommand)
+                              slaveOk, runCommand, retrieveServerData)
 
 adminCommand :: Command -> Pipe -> IO Document
 -- ^ Run command against admin database on server connected to pipe. Fail if connection fails.
@@ -113,7 +119,10 @@ connect' :: Secs -> Host -> IO Pipe
 connect' timeoutSecs (Host hostname port) = do
     mh <- timeout (round $ timeoutSecs * 1000000) (connectTo hostname port)
     handle <- maybe (ioError $ userError "connect timed out") return mh
-    newPipe handle
+    rec
+      p <- newPipe sd handle
+      sd <- access p slaveOk "admin" retrieveServerData
+    return p
 
 -- * Replica Set
 

Database/MongoDB/Internal/Protocol.hs

@@ -28,7 +28,7 @@ module Database.MongoDB.Internal.Protocol (
     Reply(..), ResponseFlag(..),
     -- * Authentication
     Username, Password, Nonce, pwHash, pwKey,
-    isClosed, close
+    isClosed, close, ServerData(..), Pipeline(..)
 ) where
 
 #if !MIN_VERSION_base(4,8,0)
@@ -83,15 +83,22 @@ mkWeakMVar = addMVarFinalizer
 -- * Pipeline
 
 -- | Thread-safe and pipelined connection
-data Pipeline = Pipeline {
-    vStream :: MVar Transport,  -- ^ Mutex on handle, so only one thread at a time can write to it
-    responseQueue :: Chan (MVar (Either IOError Response)),  -- ^ Queue of threads waiting for responses. Every time a response arrive we pop the next thread and give it the response.
-    listenThread :: ThreadId
+data Pipeline = Pipeline
+    { vStream :: MVar Transport -- ^ Mutex on handle, so only one thread at a time can write to it
+    , responseQueue :: Chan (MVar (Either IOError Response)) -- ^ Queue of threads waiting for responses. Every time a response arrive we pop the next thread and give it the response.
+    , listenThread :: ThreadId
+    , serverData :: ServerData
     }
 
+data ServerData = ServerData
+                { isMaster :: Bool
+                , minWireVersion :: Int
+                , maxWireVersion :: Int
+                }
+
 -- | Create new Pipeline over given handle. You should 'close' pipeline when finished, which will also close handle. If pipeline is not closed but eventually garbage collected, it will be closed along with handle.
-newPipeline :: Transport -> IO Pipeline
-newPipeline stream = do
+newPipeline :: ServerData -> Transport -> IO Pipeline
+newPipeline serverData stream = do
     vStream <- newMVar stream
     responseQueue <- newChan
     rec
@@ -150,13 +157,13 @@ pcall p@Pipeline{..} message = withMVar vStream doCall `onException` close p  wh
 type Pipe = Pipeline
 -- ^ Thread-safe TCP connection with pipelined requests
 
-newPipe :: Handle -> IO Pipe
+newPipe :: ServerData -> Handle -> IO Pipe
 -- ^ Create pipe over handle
-newPipe handle = T.fromHandle handle >>= newPipeWith
+newPipe sd handle = T.fromHandle handle >>= (newPipeWith sd)
 
-newPipeWith :: Transport -> IO Pipe
+newPipeWith :: ServerData -> Transport -> IO Pipe
 -- ^ Create pipe over connection
-newPipeWith conn = newPipeline conn
+newPipeWith sd conn = newPipeline sd conn
 
 send :: Pipe -> [Notice] -> IO ()
 -- ^ Send notices as a contiguous batch to server with no reply. Throw IOError if connection fails.

Database/MongoDB/Query.hs

@@ -42,7 +42,7 @@ module Database.MongoDB.Query (
     MRResult, mapReduce, runMR, runMR',
     -- * Command
     Command, runCommand, runCommand1,
-    eval,
+    eval, retrieveServerData
 ) where
 
 import Prelude hiding (lookup)
@@ -84,7 +84,7 @@ import Database.MongoDB.Internal.Protocol (Reply(..), QueryOption(..),
                                            Request(GetMore, qOptions, qSkip,
                                            qFullCollection, qBatchSize,
                                            qSelector, qProjector),
-                                           pwKey)
+                                           pwKey, ServerData(..))
 import Database.MongoDB.Internal.Util (loop, liftIOE, true1, (<.>))
 import qualified Database.MongoDB.Internal.Protocol as P
 
@@ -99,6 +99,7 @@ import qualified Crypto.MAC.HMAC as HMAC
 import Data.Bits (xor)
 import qualified Data.Map as Map
 import Text.Read (readMaybe)
+import Data.Maybe (fromMaybe)
 
 #if !MIN_VERSION_base(4,6,0)
 --mkWeakMVar = addMVarFinalizer
@@ -296,6 +297,16 @@ parseSCRAM :: B.ByteString -> Map.Map B.ByteString B.ByteString
 parseSCRAM = Map.fromList . fmap cleanup . (fmap $ T.breakOn "=") . T.splitOn "," . T.pack . B.unpack
     where cleanup (t1, t2) = (B.pack $ T.unpack t1, B.pack . T.unpack $ T.drop 1 t2)
 
+retrieveServerData :: (MonadIO m) => Action m ServerData
+retrieveServerData = do
+  d <- runCommand1 "isMaster"
+  let newSd = ServerData
+                { isMaster = (fromMaybe False $ lookup "ismaster" d)
+                , minWireVersion = (fromMaybe 0 $ lookup "minWireVersion" d)
+                , maxWireVersion = (fromMaybe 0 $ lookup "maxWireVersion" d)
+                }
+  return newSd
+
 -- * Collection
 
 type Collection = Text

Database/MongoDB/Transport/Tls.hs

@@ -1,6 +1,13 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
 
+#if (__GLASGOW_HASKELL__ >= 706)
+{-# LANGUAGE RecursiveDo #-}
+#else
+{-# LANGUAGE DoRec #-}
+#endif
+
 {-|
 Module      : MongoDB TLS
 Description : TLS transport for mongodb
@@ -36,6 +43,7 @@ import System.IO.Error (mkIOError, eofErrorType)
 import Network (connectTo, HostName, PortID)
 import qualified Network.TLS as TLS
 import qualified Network.TLS.Extra.Cipher as TLS
+import Database.MongoDB.Query (access, slaveOk, retrieveServerData)
 
 -- | Connect to mongodb using TLS
 connect :: HostName -> PortID -> IO Pipe
@@ -51,7 +59,10 @@ connect host port = bracketOnError (connectTo host port) hClose $ \handle -> do
   TLS.handshake context
 
   conn <- tlsConnection context
-  newPipeWith conn
+  rec
+    p <- newPipeWith sd conn
+    sd <- access p slaveOk "admin" retrieveServerData
+  return p
 
 tlsConnection :: TLS.Context -> IO Transport
 tlsConnection ctx = do