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Diffstat (limited to 'src/leap/common/events/component.py')
| -rw-r--r-- | src/leap/common/events/component.py | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/src/leap/common/events/component.py b/src/leap/common/events/component.py new file mode 100644 index 0000000..4fcd6e7 --- /dev/null +++ b/src/leap/common/events/component.py @@ -0,0 +1,233 @@ +# -*- coding: utf-8 -*- +# component.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + +""" +The component end point of the events mechanism. + +Components are the communicating parties of the events mechanism. They +communicate by sending messages to a server, which in turn redistributes +messages to other components. + +When a component registers a callback for a given signal, it also tells the +server that it wants to be notified whenever signals of that type are sent by +some other component. +""" + + +import logging +import threading + + +from protobuf.socketrpc import RpcService +from leap.common.events import ( + events_pb2 as proto, + server, + daemon, + mac_auth, +) + + +logger = logging.getLogger(__name__) + + +# the `registered_callbacks` dictionary below should have the following +# format: +# +# { event_signal: [ (uid, callback), ... ], ... } +# +registered_callbacks = {} + + +class CallbackAlreadyRegistered(Exception): + """ + Raised when trying to register an already registered callback. + """ + + +def ensure_component_daemon(): + """ + Ensure the component daemon is running and listening for incoming + messages. + + @return: the daemon instance + @rtype: EventsComponentDaemon + """ + daemon = EventsComponentDaemon.ensure(0) + import time + # Because we use a random port we want to wait until a port is assigned to + # local component daemon. + while not (EventsComponentDaemon.get_instance() and + EventsComponentDaemon.get_instance().get_port()): + time.sleep(0.1) + return daemon + + +def register(signal, callback, uid=None, replace=False, reqcbk=None, + timeout=1000): + """ + Registers a callback to be called when a specific signal event is + received. + + Will timeout after timeout ms if response has not been received. The + timeout arg is only used for asynch requests. If a reqcbk callback has + been supplied the timeout arg is not used. The response value will be + returned for a synch request but nothing will be returned for an asynch + request. + + @param signal: the signal that causes the callback to be launched + @type signal: int (see the `events.proto` file) + @param callback: the callback to be called when the signal is received + @type callback: function + callback(leap.common.events.events_pb2.SignalRequest) + @param uid: a unique id for the callback + @type uid: int + @param replace: should an existent callback with same uid be replaced? + @type replace: bool + @param reqcbk: a callback to be called when a response from server is + received + @type reqcbk: function + callback(leap.common.events.events_pb2.EventResponse) + @param timeout: the timeout for synch calls + @type timeout: int + + Might raise a CallbackAlreadyRegistered exception if there's already a + callback identified by the given uid and replace is False. + + @return: the response from server for synch calls or nothing for asynch + calls + @rtype: leap.common.events.events_pb2.EventsResponse or None + """ + ensure_component_daemon() # so we can receive registered signals + # register callback locally + if signal not in registered_callbacks: + registered_callbacks[signal] = [] + cbklist = registered_callbacks[signal] + if uid and filter(lambda (x, y): x == uid, cbklist): + if not replace: + raise CallbackAlreadyRegisteredException() + else: + registered_callbacks[signal] = filter(lambda(x, y): x != uid, + cbklist) + registered_callbacks[signal].append((uid, callback)) + # register callback on server + request = proto.RegisterRequest() + request.event = signal + request.port = EventsComponentDaemon.get_instance().get_port() + request.mac_method = mac_auth.MacMethod.MAC_NONE + request.mac = "" + service = RpcService(proto.EventsServerService_Stub, + server.SERVER_PORT, 'localhost') + logger.info("Sending registration request to server: %s", str(request)) + return service.register(request, callback=reqcbk, timeout=timeout) + + +def signal(signal, content="", mac_method="", mac="", reqcbk=None, + timeout=1000): + """ + Send `signal` event to events server. + + Will timeout after timeout ms if response has not been received. The + timeout arg is only used for asynch requests. If a reqcbk callback has + been supplied the timeout arg is not used. The response value will be + returned for a synch request but nothing will be returned for an asynch + request. + + @param signal: the signal that causes the callback to be launched + @type signal: int (see the `events.proto` file) + @param content: the contents of the event signal + @type content: str + @param mac_method: the method used for auth mac + @type mac_method: str + @param mac: the content of the auth mac + @type mac: str + @param reqcbk: a callback to be called when a response from server is + received + @type reqcbk: function + callback(leap.common.events.events_pb2.EventResponse) + @param timeout: the timeout for synch calls + @type timeout: int + + @return: the response from server for synch calls or nothing for asynch + calls + @rtype: leap.common.events.events_pb2.EventsResponse or None + """ + request = proto.SignalRequest() + request.event = signal + request.content = content + request.mac_method = mac_method + request.mac = mac + service = RpcService(proto.EventsServerService_Stub, server.SERVER_PORT, + 'localhost') + logger.info("Sending signal to server: %s", str(request)) + return service.signal(request, callback=reqcbk, timeout=timeout) + + +class EventsComponentService(proto.EventsComponentService): + """ + Service for receiving signal events in components. + """ + + def __init__(self): + proto.EventsComponentService.__init__(self) + + def signal(self, controller, request, done): + """ + Receive a signal and run callbacks registered for that signal. + + This method is called whenever a signal request is received from + server. + + @param controller: used to mediate a single method call + @type controller: protobuf.socketrpc.controller.SocketRpcController + @param request: the request received from the component + @type request: leap.common.events.events_pb2.SignalRequest + @param done: callback to be called when done + @type done: protobuf.socketrpc.server.Callback + """ + logger.info('Received signal from server: %s' % str(request)) + + # run registered callbacks + # TODO: verify authentication using mac in incoming message + if request.event in registered_callbacks: + for (_, cbk) in registered_callbacks[request.event]: + # callbacks should be prepared to receive a + # events_pb2.SignalRequest. + cbk(request) + + # send response back to server + response = proto.EventResponse() + response.status = proto.EventResponse.OK + done.run(response) + + +class EventsComponentDaemon(daemon.EventsSingletonDaemon): + """ + A daemon that listens for incoming events from server. + """ + + @classmethod + def ensure(cls, port): + """ + Make sure the daemon is running on the given port. + + @param port: the port in which the daemon should listen + @type port: int + + @return: a daemon instance + @rtype: EventsComponentDaemon + """ + return cls.ensure_service(port, EventsComponentService()) |