Split RabbitMQ channel create and consumer create.

Because when channel create the Subscribe is not register, so the previously stored message may lose. This fix split the channel create and consumer create, when Subscribe registered then call the consumer create function.

src/BuildingBlocks/EventBus/EventBusRabbitMQ/EventBusRabbitMQ.cs

@@ -98,7 +98,7 @@ namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
 
                     channel.BasicPublish(exchange: BROKER_NAME,
                                      routingKey: eventName,
-                                     mandatory:true,
+                                     mandatory: true,
                                      basicProperties: properties,
                                      body: body);
                 });
@@ -112,6 +112,7 @@ namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
 
             DoInternalSubscription(eventName);
             _subsManager.AddDynamicSubscription<TH>(eventName);
+            StartBasicConsume();
         }
 
         public void Subscribe<T, TH>()
@@ -124,6 +125,7 @@ namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
             _logger.LogInformation("Subscribing to event {EventName} with {EventHandler}", eventName, typeof(TH).GetGenericTypeName());
 
             _subsManager.AddSubscription<T, TH>();
+            StartBasicConsume();
         }
 
         private void DoInternalSubscription(string eventName)
@@ -172,6 +174,31 @@ namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
             _subsManager.Clear();
         }
 
+        private void StartBasicConsume()
+        {
+            if (_consumerChannel != null)
+            {
+                var consumer = new EventingBasicConsumer(_consumerChannel);
+                consumer.Received += async (model, ea) =>
+                {
+                    var eventName = ea.RoutingKey;
+                    var message = Encoding.UTF8.GetString(ea.Body);
+
+                    await ProcessEvent(eventName, message);
+
+                    _consumerChannel.BasicAck(ea.DeliveryTag, multiple: false);
+                };
+
+                _consumerChannel.BasicConsume(queue: _queueName,
+                                     autoAck: false,
+                                     consumer: consumer);
+            }
+            else
+            {
+                _logger.LogError("StartBasicConsume can not call on _consumerChannelCreated == false");
+            }
+        }
+
         private IModel CreateConsumerChannel()
         {
             if (!_persistentConnection.IsConnected)
@@ -190,26 +217,11 @@ namespace Microsoft.eShopOnContainers.BuildingBlocks.EventBusRabbitMQ
                                  autoDelete: false,
                                  arguments: null);
 
-
-            var consumer = new EventingBasicConsumer(channel);
-            consumer.Received += async (model, ea) =>
-            {
-                var eventName = ea.RoutingKey;
-                var message = Encoding.UTF8.GetString(ea.Body);
-
-                await ProcessEvent(eventName, message);
-
-                channel.BasicAck(ea.DeliveryTag,multiple:false);
-            };
-
-            channel.BasicConsume(queue: _queueName,
-                                 autoAck: false,
-                                 consumer: consumer);
-
             channel.CallbackException += (sender, ea) =>
             {
                 _consumerChannel.Dispose();
                 _consumerChannel = CreateConsumerChannel();
+                StartBasicConsume();
             };
 
             return channel;