implemented publisher side message confirmation

src/modules/messaging/MessageManager.py

 import pika
+from pika import spec
 from threading import Thread
 import network_constants as netconst
 
@@ -47,10 +48,18 @@ class MessageManager:
         if self._error_callback != None:
             self._error_callback("Connection closed")
 
+    def _message_confirmed_callback(self, frame):
+        if isinstance(frame.method, spec.Basic.Ack):
+            LOGGER.debug("message acknowledged")
+            return
+        else:
+            LOGGER.warning("Message was rejected by broker!")
+
     def _channel_created_callback(self, channel: pika.channel.Channel):
         # Assign both channels
         if self._send_channel == None:
             self._send_channel = channel
+            self._send_channel.confirm_delivery(ack_nack_callback=self._message_confirmed_callback)
         else:
             self._receive_channel = channel
             LOGGER.info("RabbitMQ connection established")
@@ -91,7 +100,10 @@ class MessageManager:
 
     def send_message(self, exchange_name, routing_key, message):
         '''Sends a message to the exchange'''
-        self._send_channel.basic_publish(exchange_name, routing_key, message)
+        try:
+            self._send_channel.basic_publish(exchange_name, routing_key, message, mandatory=True)
+        except pika.exceptions.UnroutableError:
+            raise pika.exceptions.UnroutableError
             
     def disconnect(self):
         '''Stops listening for messages and closes the connection'''

src/modules/messaging/ReconnectingMessageManager.py

@@ -3,6 +3,8 @@ import time
 from messaging.MessageManager import MessageManager
 
 import logging
+import json
+import pika
 LOGGER = logging.getLogger(__name__)
 
 class ReconnectingMessageManager:
@@ -91,5 +93,13 @@ class ReconnectingMessageManager:
         '''Sends a message to the exchange'''
         try:
             self._message_manager.send_message(exchange_name, routing_key, message)
+        except pika.exceptions.UnroutableError:
+            message = json.loads(message)
+            if message["retries"] < 10:
+                message["retries"] += 1
+                message = json.dumps(message)
+                self.send_message(exchange_name, routing_key, message)
+            else:
+                LOGGER.error("Message went through too many send retries and was not delivered")
         except:
             LOGGER.error("Error while sending message")

src/rest-gateway/app/routes/blockchain_trace.py

@@ -9,7 +9,7 @@ def receive():
     body = request.json
     
     if isBlockchainTraceValid(body):
-        message = {'type': 'blockchain-transaction', 'content': body}
+        message = {'type': 'blockchain-transaction', 'retries': 0, 'content': body}
         message_sender.send_message('inhub', 'trace-retrieval', json.dumps(message))
         return Response(status=201)