General cleanup of kernelmanager.py.

* Old handlers code removed.
* Comments added.

IPython/zmq/kernelmanager.py

@@ -76,11 +76,7 b' class ZmqSocketChannel(Thread):'
 
 class SubSocketChannel(ZmqSocketChannel):
 
-    handlers = None
-    _overriden_call_handler = None
-
     def __init__(self, context, session, address=None):
-        self.handlers = {}
         super(SubSocketChannel, self).__init__(context, session, address)
 
     def run(self):
@@ -105,53 +101,22 b' class SubSocketChannel(ZmqSocketChannel):'
             self._handle_recv()
 
     def _handle_err(self):
+        # We don't want to let this go silently, so eventually we should log.
         raise zmq.ZmqError()
 
     def _handle_recv(self):
         msg = self.socket.recv_json()
         self.call_handlers(msg)
 
-    def override_call_handler(self, func):
-        """Permanently override the call_handler.
-    
-        The function func will be called as::
-
-            func(handler, msg)
-
-        And must call::
-        
-            handler(msg)
-
-        in the main thread.
-        """
-        assert callable(func), "not a callable: %r" % func
-        self._overriden_call_handler = func
-
     def call_handlers(self, msg):
-        handler = self.handlers.get(msg['msg_type'], None)
-        if handler is not None:
-            try:
-                self.call_handler(handler, msg)
-            except:
-                # XXX: This should be logged at least
-                traceback.print_last()
+        """This method is called in the ioloop thread when a message arrives.
 
-    def call_handler(self, handler, msg):
-        if self._overriden_call_handler is not None:
-            self._overriden_call_handler(handler, msg)
-        elif hasattr(self, '_call_handler'):
-           call_handler = getattr(self, '_call_handler')
-           call_handler(handler, msg)
-        else:
-            raise RuntimeError('no handler!')
-
-    def add_handler(self, callback, msg_type):
-        """Register a callback for msg type."""
-        self.handlers[msg_type] = callback
-
-    def remove_handler(self, msg_type):
-        """Remove the callback for msg type."""
-        self.handlers.pop(msg_type, None)
+        Subclasses should override this method to handle incoming messages.
+        It is important to remember that this method is called in the thread
+        so that some logic must be done to ensure that the application leve
+        handlers are called in the application thread.
+        """
+        raise NotImplementedError('call_handlers must be defined in a subclass.')
 
     def flush(self, timeout=1.0):
         """Immediately processes all pending messages on the SUB channel.
@@ -228,6 +193,7 b' class XReqSocketChannel(ZmqSocketChannel):'
             self.socket.send_json(msg)
 
     def _handle_err(self):
+        # We don't want to let this go silently, so eventually we should log.
         raise zmq.ZmqError()
 
     def _queue_request(self, msg, callback):