Rename withDynamic to withEphemeralPorts and cleanup

ipython-kernel/src/IHaskell/IPython/ZeroMQ.hs

@@ -10,8 +10,8 @@ module IHaskell.IPython.ZeroMQ
        , ZeroMQStdin(..)
        , serveProfile
        , serveStdin
-       , ZeroMQDynamicPorts(..)
-       , withDynamic
+       , ZeroMQEphemeralPorts(..)
+       , withEphemeralPorts
        ) where
 
 import           Control.Concurrent
@@ -26,7 +26,8 @@ import           Data.Digest.Pure.SHA as SHA
 import           Data.Monoid ((<>))
 import qualified Data.Text.Encoding as Text
 import           System.IO.Unsafe
-import           System.ZMQ4 hiding (stdin)
+import           System.ZMQ4 as ZMQ4 hiding (stdin)
+import           Text.Read (readMaybe)
 
 import           IHaskell.IPython.Types
 import           IHaskell.IPython.Message.Parser
@@ -91,44 +92,50 @@ serveProfile profile debug = do
 
   return channels
 
-data ZeroMQDynamicPorts
-   = ZeroMQDynamicPorts { dynHbPort      :: !Port
-                        , dynControlPort :: !Port
-                        , dynShellPort   :: !Port
-                        , dynIOPubPort   :: !Port
-                        , dynSignatureKey  :: !ByteString
-                        }
+data ZeroMQEphemeralPorts
+   = ZeroMQEphemeralPorts { ephHbPort      :: !Port
+                          , ephControlPort :: !Port
+                          , ephShellPort   :: !Port
+                          , ephIOPubPort   :: !Port
+                          , ephSignatureKey  :: !ByteString
+                          }
 
-instance ToJSON ZeroMQDynamicPorts where
+instance ToJSON ZeroMQEphemeralPorts where
   toJSON ports =
     object [ "ip"           .= ("127.0.0.1" :: String)
            , "transport"    .= TCP
-           , "control_port" .= dynControlPort ports
-           , "hb_port"      .= dynHbPort ports
-           , "shell_port"   .= dynShellPort ports
-           , "iopub_port"   .= dynIOPubPort ports
-           , "key" .= Text.decodeUtf8 (dynSignatureKey ports)
+           , "control_port" .= ephControlPort ports
+           , "hb_port"      .= ephHbPort ports
+           , "shell_port"   .= ephShellPort ports
+           , "iopub_port"   .= ephIOPubPort ports
+           , "key"          .= Text.decodeUtf8 (ephSignatureKey ports)
            ]
 
-parsePort :: String -> Int
-parsePort s = read num
+parsePort :: String -> Maybe Int
+parsePort s = readMaybe num
   where num = reverse (takeWhile isNumber (reverse s))
 
-bindLocalDynamicPort :: Socket a -> IO Int
-bindLocalDynamicPort socket = do
+bindLocalEphemeralPort :: Socket a -> IO Int
+bindLocalEphemeralPort socket = do
   bind socket   $ "tcp://127.0.0.1:*"
-  parsePort <$> lastEndpoint socket
+  endpointString <- lastEndpoint socket
+  case parsePort endpointString of
+    Nothing ->
+      fail $ "internalError: IHaskell.IPython.ZeroMQ.bindLocalEphemeralPort encountered a port index that could not be interpreted as an int."
+    Just endpointIndex ->
+      return endpointIndex
 
 -- | Start responding on all ZeroMQ channels used to communicate with IPython
--- | with dynamic ports.
--- Profide the callback with the dynamic ports chosen and a ZeroMQInterface.
-withDynamic :: ByteString
-               -- ^ HMAC encryption key
-            -> Bool               -- ^ Print debug output
-            -> (ZeroMQDynamicPorts -> ZeroMQInterface -> IO a)
-               -- ^ Callback that takes the interface to the sockets.
-            -> IO a
-withDynamic key debug callback = do
+-- with ephemerally allocated ports.
+-- Profide the callback with the ports chosen and a ZeroMQInterface.
+withEphemeralPorts :: ByteString
+                      -- ^ HMAC encryption key
+                      -> Bool
+                      -- ^ Print debug output
+                      -> (ZeroMQEphemeralPorts -> ZeroMQInterface -> IO a)
+                      -- ^ Callback that takes the interface to the sockets.
+                      -> IO a
+withEphemeralPorts key debug callback = do
   -- Create all channels which will be used for higher level communication.
   shellReqChan <- newChan
   shellRepChan <- newChan
@@ -137,31 +144,31 @@ withDynamic key debug callback = do
   iopubChan <- newChan
   let channels = Channels shellReqChan shellRepChan controlReqChan controlRepChan iopubChan key
 
-  -- Create the context in a separate thread that never finishes. If withContext or withSocket
-  -- complete, the context or socket become invalid.
+  -- Create the ZMQ4 context
   withContext $ \context -> do
-   -- Serve on all sockets.
-   withSocket context Rep    $ \heartbeat_socket -> do
-    withSocket context Router $ \controlport_socket -> do
-     withSocket context Router $ \shellport_socket -> do
-      withSocket context Pub    $ \iopub_socket -> do
+   -- Create the sockets to communicate with.
+   withSocket context Rep $ \heartbeatSocket -> do
+    withSocket context Router $ \controlportSocket -> do
+     withSocket context Router $ \shellportSocket -> do
+      withSocket context Pub    $ \iopubSocket -> do
 
-       dyn_hb_port      <- bindLocalDynamicPort heartbeat_socket
-       dyn_control_port <- bindLocalDynamicPort controlport_socket
-       dyn_shell_port <- bindLocalDynamicPort shellport_socket
-       dyn_iopub_port <- bindLocalDynamicPort iopub_socket
+       -- Bind each socket to a local port, getting the port chosen.
+       hbPort      <- bindLocalEphemeralPort heartbeatSocket
+       controlPort <- bindLocalEphemeralPort controlportSocket
+       shellPort   <- bindLocalEphemeralPort shellportSocket
+       iopubPort   <- bindLocalEphemeralPort iopubSocket
 
-       _ <- forkIO $ forever $ heartbeat channels heartbeat_socket
-       _ <- forkIO $ forever $ control debug channels controlport_socket
-       _ <- forkIO $ forever $ shell debug channels shellport_socket
-       _ <- forkIO $ forever $ checked_iopub debug channels iopub_socket
+       _ <- forkIO $ forever $ heartbeat channels heartbeatSocket
+       _ <- forkIO $ forever $ control debug channels controlportSocket
+       _ <- forkIO $ forever $ shell debug channels shellportSocket
+       _ <- forkIO $ forever $ checkedIOpub debug channels iopubSocket
 
-       let ports = ZeroMQDynamicPorts { dynHbPort      = dyn_hb_port
-                                      , dynControlPort = dyn_control_port
-                                      , dynShellPort   = dyn_shell_port
-                                      , dynIOPubPort   = dyn_iopub_port
-                                      , dynSignatureKey = key
-                                      }
+       let ports = ZeroMQEphemeralPorts { ephHbPort      = hbPort
+                                        , ephControlPort = controlPort
+                                        , ephShellPort   = shellPort
+                                        , ephIOPubPort   = iopubPort
+                                        , ephSignatureKey = key
+                                        }
        callback ports channels
 
 serveStdin :: Profile -> IO ZeroMQStdin
@@ -237,17 +244,17 @@ iopub debug channels socket =
 
 -- | Send messages via the iopub channel. | This reads messages from the ZeroMQ iopub interface
 -- channel | and then writes the messages to the socket.
-checked_iopub :: Bool -> ZeroMQInterface -> Socket Pub -> IO ()
-checked_iopub debug channels socket = do
+checkedIOpub :: Bool -> ZeroMQInterface -> Socket Pub -> IO ()
+checkedIOpub debug channels socket = do
   msg <- readChan (iopubChannel channels)
-  let error_handler :: ZMQError -> IO ()
-      error_handler e
+  let errorHandler :: ZMQError -> IO ()
+      errorHandler e
           -- Ignore errors if we cannot send.
           -- We may want to cascade this back to channel.
         | errno e == 38 = return ()
         | otherwise = throwIO e
   catch (sendMessage debug (hmacKey channels) socket msg)
-        error_handler
+        errorHandler
 
 -- | Receive and parse a message from a socket.
 receiveMessage :: Receiver a => Bool -> Socket a -> IO Message