Add a server for events mechanism.

1 files changed, 150 insertions, 0 deletions

diff --git a/src/leap/common/events/server.py b/src/leap/common/events/server.py
new file mode 100644
index 0000000..5cc1add
--- /dev/null
+++ b/src/leap/common/events/server.py
@@ -0,0 +1,150 @@
+# -*- coding: utf-8 -*-
+# server.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/>.
+
+"""
+A server for the events mechanism.
+
+A server can receive different kinds of requests from components:
+
+  1. Registration request: store component port number to be notified when
+     a specific signal arrives.
+
+  2. Signal request: redistribute the signal to registered components.
+"""
+
+
+import logging
+import sets
+
+
+from protobuf.socketrpc import RpcService
+from leap.common.events import (
+    events_pb2 as proto,
+    daemon,
+)
+
+
+logger = logging.getLogger(__name__)
+
+
+SERVER_PORT = 8090
+
+# the `registered_components` dictionary below should have the following
+# format:
+#
+#     { event_signal: [ port, ... ], ... }
+#
+registered_components = {}
+
+
+def ensure_server(port=SERVER_PORT):
+    """
+    Make sure the server is running on the given port.
+
+    Attempt to connect to given local port. Upon success, assume that the
+    events server has already been started. Upon failure, start events server.
+
+    @param port: the port in which server should be listening
+    @type port: int
+
+    @return: the daemon instance or nothing
+    @rtype: EventsServerDaemon or None
+    """
+    try:
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.connect(('localhost', port))
+        s.close()
+        logger.info('Server is already running on port %d.', port)
+        return None
+    except socket.error:
+        logger.info('Launching server on port %d.', port)
+        return EventsServerDaemon.ensure(port)
+
+
+class EventsServerService(proto.EventsServerService):
+    """
+    Service for receiving events in components.
+    """
+
+    def register(self, controller, request, done):
+        """
+        Register a component port to be signaled when specific events come in.
+
+        @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.RegisterRequest
+        @param done: callback to be called when done
+        @type done: protobuf.socketrpc.server.Callback
+        """
+        logger.info("Received registration request: %s" % str(request))
+        # add component port to signal list
+        if request.event not in registered_components:
+            registered_components[request.event] = sets.Set()
+        registered_components[request.event].add(request.port)
+        # send response back to component
+        response = proto.EventResponse()
+        response.status = proto.EventResponse.OK
+        done.run(response)
+
+    def signal(self, controller, request, done):
+        """
+        Perform an RPC call to signal all components registered to receive a
+        specific signal.
+
+        @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 component: %s', str(request))
+        # send signal to all registered components
+        # TODO: verify signal auth
+        if request.event in registered_components:
+            for port in registered_components[request.event]:
+
+                def callback(req, resp):
+                    logger.info("Signal received by " + str(port))
+
+                service = RpcService(proto.EventsComponentService_Stub,
+                                     port, 'localhost')
+                service.signal(request, callback=callback)
+        # send response back to component
+        response = proto.EventResponse()
+        response.status = proto.EventResponse.OK
+        done.run(response)
+
+
+class EventsServerDaemon(daemon.EventsSingletonDaemon):
+    """
+    Singleton class for starting an events server daemon.
+    """
+
+    @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: EventsServerDaemon
+        """
+        return cls.ensure_service(port, EventsServerService())