Deliver notification info

Created by: stefanoborini

Notification system to communicate to the UI and other entities interested in notification.

force_bdss/core_plugins/dummy/ui_notification/ui_notification.py

-from traits.api import Any
+from traits.api import Any, List
 
 from force_bdss.api import BaseNotificationListener
 import zmq
 
 
 class UINotification(BaseNotificationListener):
-    _zmq_context = Any()
-    _zmq_socket = Any()
+    _context = Any()
+    _pub_socket = Any()
+    _rep_socket = Any()
+    _msg_cache = List()
 
     def deliver(self, model, message):
-        self._zmq_socket.send(("ACTION {}".format(message)).encode("utf-8"))
+        try:
+            data = self._rep_socket.recv(flags=zmq.NOBLOCK)
+        except zmq.ZMQError:
+            pass
+        else:
+            self._rep_socket.send_multipart(self._msg_cache)
+
+        msg = "ACTION {}".format(message).encode("utf-8")
+        self._msg_cache.append(msg)
+        self._pub_socket.send(msg)
 
     def init_persistent_state(self, model):
-        self._zmq_context = zmq.Context()
-        self._zmq_socket = self._zmq_context.socket(zmq.PUB)
-        self._zmq_socket.bind("tcp://*:12345")
+        self._context = zmq.Context()
+        self._pub_socket = self._context.socket(zmq.PUB)
+        self._pub_socket.bind("tcp://*:12345")
+
+        self._rep_socket = self._context.socket(zmq.REP)
+        self._rep_socket.bind("tcp://*:12346")