Fixed high CPU usage of XREQ channel.

Previously, the XReqSocketChannel was consuming nearly 100% CPU.
This was caused by the ioloop polling for POLLIN|POLLOUT|POLLERR
always. Now we are only polling for POLLOUT when there is a
message waiting to be sent. This seems to have fixed the problem.

IPython/frontend/qt/kernelmanager.py

@@ -1,144 +1,147
 """ Defines a KernelManager that provides signals and slots.
 """
 
 # System library imports.
 from PyQt4 import QtCore
+import zmq
 
 # IPython imports.
 from IPython.zmq.kernelmanager import KernelManager, SubSocketChannel, \
     XReqSocketChannel, RepSocketChannel
 from util import MetaQObjectHasTraits
 
 
+
 class QtSubSocketChannel(SubSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyout' or 'stdout' is received.
     output_received = QtCore.pyqtSignal(object)
 
     # Emitted when a message of type 'pyerr' or 'stderr' is received.
     error_received = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         SubSocketChannel.__init__(self, *args, **kw)
 
     #---------------------------------------------------------------------------
     # 'SubSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         if msg_type in ('pyout', 'stdout'):
             self.output_received.emit(msg)
         elif msg_type in ('pyerr', 'stderr'):
             self.error_received.emit(msg)
 
     def flush(self):
         """ Reimplemented to ensure that signals are dispatched immediately.
         """
         super(QtSubSocketChannel, self).flush()
         QtCore.QCoreApplication.instance().processEvents()
 
 
 class QtXReqSocketChannel(XReqSocketChannel, QtCore.QObject):
 
     # Emitted when any message is received.
     message_received = QtCore.pyqtSignal(object)
 
     # Emitted when a reply has been received for the corresponding request type.
     execute_reply = QtCore.pyqtSignal(object)
     complete_reply = QtCore.pyqtSignal(object)
     object_info_reply = QtCore.pyqtSignal(object)
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         XReqSocketChannel.__init__(self, *args, **kw)
     
     #---------------------------------------------------------------------------
     # 'XReqSocketChannel' interface
     #---------------------------------------------------------------------------
     
     def call_handlers(self, msg):
         """ Reimplemented to emit signals instead of making callbacks.
         """
         # Emit the generic signal.
         self.message_received.emit(msg)
         
         # Emit signals for specialized message types.
         msg_type = msg['msg_type']
         signal = getattr(self, msg_type, None)
         if signal:
             signal.emit(msg)
 
     def _queue_request(self, msg, callback):
         """ Reimplemented to skip callback handling.
         """
         self.command_queue.put(msg)
+        self.add_io_state(zmq.POLLOUT)
 
 
 class QtRepSocketChannel(RepSocketChannel, QtCore.QObject):
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
     
     def __init__(self, *args, **kw):
         """ Reimplemented to ensure that QtCore.QObject is initialized first.
         """
         QtCore.QObject.__init__(self)
         RepSocketChannel.__init__(self, *args, **kw)
 
 
 class QtKernelManager(KernelManager, QtCore.QObject):
     """ A KernelManager that provides signals and slots.
     """
 
     __metaclass__ = MetaQObjectHasTraits
 
     # Emitted when the kernel manager has started listening.
     started_listening = QtCore.pyqtSignal()
 
     # Emitted when the kernel manager has stopped listening.
     stopped_listening = QtCore.pyqtSignal()
 
     # Use Qt-specific channel classes that emit signals.
     sub_channel_class = QtSubSocketChannel
     xreq_channel_class = QtXReqSocketChannel
     rep_channel_class = QtRepSocketChannel
 
     #---------------------------------------------------------------------------
     # 'KernelManager' interface
     #---------------------------------------------------------------------------
     
     def start_listening(self):
         """ Reimplemented to emit signal.
         """
         super(QtKernelManager, self).start_listening()
         self.started_listening.emit()
 
     def stop_listening(self):
         """ Reimplemented to emit signal.
         """ 
         super(QtKernelManager, self).stop_listening()
         self.stopped_listening.emit()

IPython/zmq/kernelmanager.py

@@ -1,466 +1,497
 """Kernel frontend classes.
 
 TODO: Create logger to handle debugging and console messages.
 
 """
 
 # Standard library imports.
 from Queue import Queue, Empty
 from subprocess import Popen
 from threading import Thread
 import time
 import traceback
 
 # System library imports.
 import zmq
 from zmq import POLLIN, POLLOUT, POLLERR
 from zmq.eventloop import ioloop
 
 # Local imports.
 from IPython.utils.traitlets import HasTraits, Any, Bool, Int, Instance, Str, \
     Type
 from kernel import launch_kernel
 from session import Session
 
 # Constants.
 LOCALHOST = '127.0.0.1'
 
 
 class MissingHandlerError(Exception):
     pass
 
 
 class ZmqSocketChannel(Thread):
     """ The base class for the channels that use ZMQ sockets.
     """
 
+    context = None
+    session = None
+    socket = None
+    ioloop = None
+    iostate = None
+
     def __init__(self, context, session, address=None):
         super(ZmqSocketChannel, self).__init__()
         self.daemon = True
 
         self.context = context
         self.session = session
         self.address = address
-        self.socket = None
 
     def stop(self):
         """Stop the thread's activity. Returns when the thread terminates.
 
         The thread will raise :class:`RuntimeError` if :method:`self.start`
         is called again.
         """
         self.join()
 
 
     def get_address(self):
         """ Get the channel's address. By the default, a channel is on 
             localhost with no port specified (a negative port number).
         """
         return self._address
 
     def set_adresss(self, address):
         """ Set the channel's address. Should be a tuple of form:
                 (ip address [str], port [int]).
             or None, in which case the address is reset to its default value.
         """
         # FIXME: Validate address.
         if self.is_alive():  # This is Thread.is_alive
             raise RuntimeError("Cannot set address on a running channel!")
         else:
             if address is None:
                 address = (LOCALHOST, 0)
             self._address = address
 
     address = property(get_address, set_adresss)
 
+    def add_io_state(self, state):
+        """Add IO state to the eventloop.
+
+        This is thread safe as it uses the thread safe IOLoop.add_callback.
+        """
+        def add_io_state_callback():
+            if not self.iostate & state:
+                self.iostate = self.iostate | state
+                self.ioloop.update_handler(self.socket, self.iostate)
+        self.ioloop.add_callback(add_io_state_callback)
+
+    def drop_io_state(self, state):
+        """Drop IO state from the eventloop.
+
+        This is thread safe as it uses the thread safe IOLoop.add_callback.
+        """
+        def drop_io_state_callback():
+            if self.iostate & state:
+                self.iostate = self.iostate & (~state)
+                self.ioloop.update_handler(self.socket, self.iostate)
+        self.ioloop.add_callback(drop_io_state_callback)
+
 
 class SubSocketChannel(ZmqSocketChannel):
 
     def __init__(self, context, session, address=None):
         super(SubSocketChannel, self).__init__(context, session, address)
 
     def run(self):
         self.socket = self.context.socket(zmq.SUB)
         self.socket.setsockopt(zmq.SUBSCRIBE,'')
         self.socket.setsockopt(zmq.IDENTITY, self.session.session)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.ioloop = ioloop.IOLoop()
+        self.iostate = POLLIN|POLLERR
         self.ioloop.add_handler(self.socket, self._handle_events, 
-                                POLLIN|POLLERR)
+                                self.iostate)
         self.ioloop.start()
 
     def stop(self):
         self.ioloop.stop()
         super(SubSocketChannel, self).stop()
 
     def _handle_events(self, socket, events):
         # Turn on and off POLLOUT depending on if we have made a request
         if events & POLLERR:
             self._handle_err()
         if events & POLLIN:
             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):
         # Get all of the messages we can
         while True:
             try:
                 msg = self.socket.recv_json(zmq.NOBLOCK)
             except zmq.ZMQError:
                 # Check the errno?
                 # Will this tigger POLLERR?
                 break
             else:
                 self.call_handlers(msg)
 
     def call_handlers(self, msg):
         """This method is called in the ioloop thread when a message arrives.
 
         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.
 
         This method is thread safe.
 
         Parameters
         ----------
         timeout : float, optional
             The maximum amount of time to spend flushing, in seconds. The
             default is one second.
         """
         # We do the IOLoop callback process twice to ensure that the IOLoop
         # gets to perform at least one full poll.
         stop_time = time.time() + timeout
         for i in xrange(2):
             self._flushed = False
             self.ioloop.add_callback(self._flush)
             while not self._flushed and time.time() < stop_time:
                 time.sleep(0.01)
         
     def _flush(self):
         """Called in this thread by the IOLoop to indicate that all events have
         been processed.
         """
         self._flushed = True
 
 
 class XReqSocketChannel(ZmqSocketChannel):
 
     handler_queue = None
     command_queue = None
     handlers = None
     _overriden_call_handler = None
 
     def __init__(self, context, session, address=None):
         self.handlers = {}
         self.handler_queue = Queue()
         self.command_queue = Queue()
         super(XReqSocketChannel, self).__init__(context, session, address)
 
     def run(self):
         self.socket = self.context.socket(zmq.XREQ)
         self.socket.setsockopt(zmq.IDENTITY, self.session.session)
         self.socket.connect('tcp://%s:%i' % self.address)
         self.ioloop = ioloop.IOLoop()
+        self.iostate = POLLERR|POLLIN
         self.ioloop.add_handler(self.socket, self._handle_events, 
-                                POLLIN|POLLOUT|POLLERR)
+                                self.iostate)
         self.ioloop.start()
 
     def stop(self):
         self.ioloop.stop()
         super(XReqSocketChannel, self).stop()
 
     def _handle_events(self, socket, events):
-        # Turn on and off POLLOUT depending on if we have made a request
         if events & POLLERR:
             self._handle_err()
         if events & POLLOUT:
             self._handle_send()
         if events & POLLIN:
             self._handle_recv()
 
     def _handle_recv(self):
         msg = self.socket.recv_json()
         self.call_handlers(msg)
 
     def _handle_send(self):
         try:
             msg = self.command_queue.get(False)
         except Empty:
             pass
         else:
             self.socket.send_json(msg)
+        if self.command_queue.empty():
+            self.drop_io_state(POLLOUT)
 
     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):
         handler = self._find_handler(msg['msg_type'], callback)
         self.handler_queue.put(handler)
         self.command_queue.put(msg)
+        self.add_io_state(POLLOUT)
 
     def execute(self, code, callback=None):
         # Create class for content/msg creation. Related to, but possibly
         # not in Session.
         content = dict(code=code)
         msg = self.session.msg('execute_request', content)
         self._queue_request(msg, callback)
         return msg['header']['msg_id']
 
     def complete(self, text, line, block=None, callback=None):
         content = dict(text=text, line=line)
         msg = self.session.msg('complete_request', content)
         self._queue_request(msg, callback)
         return msg['header']['msg_id']
 
     def object_info(self, oname, callback=None):
         content = dict(oname=oname)
         msg = self.session.msg('object_info_request', content)
         self._queue_request(msg, callback)
         return msg['header']['msg_id']
 
     def _find_handler(self, name, callback):
         if callback is not None:
             return callback
         handler = self.handlers.get(name)
         if handler is None:
             raise MissingHandlerError(
                 'No handler defined for method: %s' % name)
         return handler
 
     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):
         try:
             handler = self.handler_queue.get(False)
         except Empty:
             print "Message received with no handler!!!"
             print msg
         else:
             self.call_handler(handler, msg)
 
     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!')
 
 
 class RepSocketChannel(ZmqSocketChannel):
 
     def on_raw_input(self):
         pass
 
 
 class KernelManager(HasTraits):
     """ Manages a kernel for a frontend.
 
     The SUB channel is for the frontend to receive messages published by the
     kernel.
         
     The REQ channel is for the frontend to make requests of the kernel.
     
     The REP channel is for the kernel to request stdin (raw_input) from the
     frontend.
     """
 
     # Whether the kernel manager is currently listening on its channels.
     is_listening = Bool(False)
 
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context, ())
 
     # The Session to use for communication with the kernel.
     session = Instance(Session, ())
 
     # The classes to use for the various channels.
     sub_channel_class = Type(SubSocketChannel)
     xreq_channel_class = Type(XReqSocketChannel)
     rep_channel_class = Type(RepSocketChannel)
     
     # Protected traits.
     _kernel = Instance(Popen)
     _sub_channel = Any
     _xreq_channel = Any
     _rep_channel = Any
 
     #--------------------------------------------------------------------------
     # Channel management methods:
     #--------------------------------------------------------------------------
 
     def start_listening(self):
         """Starts listening on the specified ports. If already listening, raises
         a RuntimeError.
         """
         if self.is_listening:
             raise RuntimeError("Cannot start listening. Already listening!")
         else:
             self.is_listening = True
             self.sub_channel.start()
             self.xreq_channel.start()
             self.rep_channel.start()
 
     @property
     def is_alive(self):
         """ Returns whether the kernel is alive. """
         if self.is_listening:
             # TODO: check if alive.
             return True
         else:
             return False
 
     def stop_listening(self):
         """Stops listening. If not listening, does nothing. """
         if self.is_listening:
             self.is_listening = False
             self.sub_channel.stop()
             self.xreq_channel.stop()
             self.rep_channel.stop()
 
     #--------------------------------------------------------------------------
     # Kernel process management methods:
     #--------------------------------------------------------------------------
 
     def start_kernel(self):
         """Starts a kernel process and configures the manager to use it.
 
         If ports have been specified via the address attributes, they are used.
         Otherwise, open ports are chosen by the OS and the channel port
         attributes are configured as appropriate.
         """
         xreq, sub = self.xreq_address, self.sub_address
         if xreq[0] != LOCALHOST or sub[0] != LOCALHOST:
             raise RuntimeError("Can only launch a kernel on localhost."
                                "Make sure that the '*_address' attributes are "
                                "configured properly.")
 
         kernel, xrep, pub = launch_kernel(xrep_port=xreq[1], pub_port=sub[1])
         self.set_kernel(kernel)
         self.xreq_address = (LOCALHOST, xrep)
         self.sub_address = (LOCALHOST, pub)
 
     def set_kernel(self, kernel):
         """Sets the kernel manager's kernel to an existing kernel process.
 
         It is *not* necessary to a set a kernel to communicate with it via the
         channels, and those objects must be configured separately. It
         *is* necessary to set a kernel if you want to use the manager (or
         frontends that use the manager) to signal and/or kill the kernel.
 
         Parameters:
         -----------
         kernel : Popen
             An existing kernel process.
         """
         self._kernel = kernel
 
     @property
     def has_kernel(self):
         """Returns whether a kernel process has been specified for the kernel
         manager.
 
         A kernel process can be set via 'start_kernel' or 'set_kernel'.
         """
         return self._kernel is not None
 
     def kill_kernel(self):
         """ Kill the running kernel. """
         if self._kernel:
             self._kernel.kill()
             self._kernel = None
         else:
             raise RuntimeError("Cannot kill kernel. No kernel is running!")
 
     def signal_kernel(self, signum):
         """ Sends a signal to the kernel. """
         if self._kernel:
             self._kernel.send_signal(signum)
         else:
             raise RuntimeError("Cannot signal kernel. No kernel is running!")
 
     #--------------------------------------------------------------------------
     # Channels used for communication with the kernel:
     #--------------------------------------------------------------------------
 
     @property
     def sub_channel(self):
         """Get the SUB socket channel object."""
         if self._sub_channel is None:
             self._sub_channel = self.sub_channel_class(self.context,
                                                        self.session)
         return self._sub_channel
 
     @property
     def xreq_channel(self):
         """Get the REQ socket channel object to make requests of the kernel."""
         if self._xreq_channel is None:
             self._xreq_channel = self.xreq_channel_class(self.context, 
                                                          self.session)
         return self._xreq_channel
 
     @property
     def rep_channel(self):
         """Get the REP socket channel object to handle stdin (raw_input)."""
         if self._rep_channel is None:
             self._rep_channel = self.rep_channel_class(self.context, 
                                                        self.session)
         return self._rep_channel
 
     #--------------------------------------------------------------------------
     # Delegates for the Channel address attributes:
     #--------------------------------------------------------------------------
 
     def get_sub_address(self):
         return self.sub_channel.address
 
     def set_sub_address(self, address):
         self.sub_channel.address = address
 
     sub_address = property(get_sub_address, set_sub_address,
                            doc="The address used by SUB socket channel.")
 
     def get_xreq_address(self):
         return self.xreq_channel.address
 
     def set_xreq_address(self, address):
         self.xreq_channel.address = address
 
     xreq_address = property(get_xreq_address, set_xreq_address,
                             doc="The address used by XREQ socket channel.")
     
     def get_rep_address(self):
         return self.rep_channel.address
 
     def set_rep_address(self, address):
         self.rep_channel.address = address
 
     rep_address = property(get_rep_address, set_rep_address,
                            doc="The address used by REP socket channel.")