Fix #23

+ add test case

hbmqtt/mqtt/protocol/handler.py

@@ -333,22 +333,26 @@ class ProtocolHandler:
             # Wait PUBREL
             if app_message.packet_id in self._pubrel_waiters and not self._pubrel_waiters[app_message.packet_id].done():
                 # PUBREL waiter already exists for this packet ID
-                message = "Can't add PUBREL waiter, a waiter already exists for message Id '%s'" \
+                message = "A waiter already exists for message Id '%s', canceling it" \
                           % app_message.packet_id
                 self.logger.warning(message)
-                raise HBMQTTException(message)
-            waiter = asyncio.Future(loop=self._loop)
-            self._pubrel_waiters[app_message.packet_id] = waiter
-            yield from waiter
-            del self._pubrel_waiters[app_message.packet_id]
-            app_message.pubrel_packet = waiter.result()
-            # Initiate delivery and discard message
-            yield from self.session.delivered_message_queue.put(app_message)
-            del self.session.inflight_in[app_message.packet_id]
-            # Send pubcomp
-            pubcomp_packet = PubcompPacket.build(app_message.packet_id)
-            yield from self._send_packet(pubcomp_packet)
-            app_message.pubcomp_packet = pubcomp_packet
+                self._pubrel_waiters[app_message.packet_id].cancel()
+            try:
+                waiter = asyncio.Future(loop=self._loop)
+                self._pubrel_waiters[app_message.packet_id] = waiter
+                yield from waiter
+                del self._pubrel_waiters[app_message.packet_id]
+                app_message.pubrel_packet = waiter.result()
+                # Initiate delivery and discard message
+                yield from self.session.delivered_message_queue.put(app_message)
+                del self.session.inflight_in[app_message.packet_id]
+                # Send pubcomp
+                pubcomp_packet = PubcompPacket.build(app_message.packet_id)
+                yield from self._send_packet(pubcomp_packet)
+                app_message.pubcomp_packet = pubcomp_packet
+            except asyncio.CancelledError:
+                self.logger.debug("Message flow cancelled")
+
 
     @asyncio.coroutine
     def _reader_loop(self):

tests/test_broker.py

@@ -6,6 +6,9 @@ from unittest.mock import patch, call, MagicMock
 from hbmqtt.broker import *
 from hbmqtt.mqtt.constants import *
 from hbmqtt.client import MQTTClient, ConnectException
+from hbmqtt.mqtt import ConnectPacket, ConnackPacket, PublishPacket, PubrecPacket, \
+    PubrelPacket, PubcompPacket, DisconnectPacket
+from hbmqtt.mqtt.connect import ConnectVariableHeader, ConnectPayload
 
 formatter = "[%(asctime)s] %(name)s {%(filename)s:%(lineno)d} %(levelname)s - %(message)s"
 logging.basicConfig(level=logging.DEBUG, format=formatter)
@@ -287,6 +290,58 @@ class BrokerTest(unittest.TestCase):
         if future.exception():
             raise future.exception()
 
+    #@patch('hbmqtt.broker.PluginManager')
+    def test_client_publish_dup(self):
+        @asyncio.coroutine
+        def test_coro():
+            try:
+                broker = Broker(test_config, plugin_namespace="hbmqtt.test.plugins")
+                yield from broker.start()
+                self.assertTrue(broker.transitions.is_started())
+
+                conn_reader, conn_writer = \
+                    yield from asyncio.open_connection('localhost', 1883, loop=self.loop)
+                reader = StreamReaderAdapter(conn_reader)
+                writer = StreamWriterAdapter(conn_writer)
+
+                vh = ConnectVariableHeader()
+                payload = ConnectPayload()
+
+                vh.keep_alive = 10
+                vh.clean_session_flag = False
+                vh.will_retain_flag = False
+                payload.client_id = 'test_id'
+                connect = ConnectPacket(vh=vh, payload=payload)
+                yield from connect.to_stream(writer)
+                yield from ConnackPacket.from_stream(reader)
+
+                publish_1 = PublishPacket.build('/test', b'data', 1, False, QOS_2, False)
+                yield from publish_1.to_stream(writer)
+                ensure_future(PubrecPacket.from_stream(reader), loop=self.loop)
+
+                yield from asyncio.sleep(2)
+
+                publish_dup = PublishPacket.build('/test', b'data', 1, True, QOS_2, False)
+                yield from publish_dup.to_stream(writer)
+                pubrec2 = yield from PubrecPacket.from_stream(reader)
+                pubrel = PubrelPacket.build(1)
+                yield from pubrel.to_stream(writer)
+                pubcomp = yield from PubcompPacket.from_stream(reader)
+
+                disconnect = DisconnectPacket()
+                yield from disconnect.to_stream(writer)
+
+                yield from asyncio.sleep(0.1)
+                yield from broker.shutdown()
+                future.set_result(True)
+            except Exception as ae:
+                future.set_exception(ae)
+
+        future = asyncio.Future(loop=self.loop)
+        self.loop.run_until_complete(test_coro())
+        if future.exception():
+            raise future.exception()
+
     @patch('hbmqtt.broker.PluginManager')
     def test_client_publish_invalid_topic(self, MockPluginManager):
         @asyncio.coroutine