Merge tag '1.2' into develop

Tapeti.Annotations/DurableQueueAttribute.cs

@@ -2,6 +2,7 @@
 
 namespace Tapeti.Annotations
 {
+    /// <inheritdoc />
     /// <summary>
     /// Binds to an existing durable queue to receive messages. Can be used
     /// on an entire MessageController class or on individual methods.
@@ -17,6 +18,8 @@ namespace Tapeti.Annotations
         public string Name { get; set; }
 
 
+        /// <inheritdoc />
+        /// <param name="name">The name of the durable queue</param>
         public DurableQueueAttribute(string name)
         {
             Name = name;

Tapeti.Annotations/DynamicQueueAttribute.cs

@@ -2,6 +2,7 @@
 
 namespace Tapeti.Annotations
 {
+    /// <inheritdoc />
     /// <summary>
     /// Creates a non-durable auto-delete queue to receive messages. Can be used
     /// on an entire MessageController class or on individual methods.
@@ -12,12 +13,10 @@ namespace Tapeti.Annotations
         public string Prefix { get; set; }
 
 
-        /// <summary>
+        /// <inheritdoc />
-        /// If prefix is specified, Tapeti will compose the queue name using the
+        /// <param name="prefix">An optional prefix. If specified, Tapeti will compose the queue name using the
-        /// prefix and a unique ID. If not specified, an empty queue name will be passed
+        /// prefix and a unique ID. If not specified, an empty queue name will be passed
-        /// to RabbitMQ thus letting it create a unique queue name.
+        /// to RabbitMQ thus letting it create a unique queue name.</param>
-        /// </summary>
-        /// <param name="prefix"></param>
         public DynamicQueueAttribute(string prefix = null)
         {
             Prefix = prefix;

Tapeti.Annotations/MandatoryAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Tapeti.Annotations
+{
+    /// <inheritdoc />
+    /// <summary>
+    /// Can be attached to a message class to specify that delivery to a queue must be guaranteed.
+    /// Publish will fail if no queues bind to the routing key. Publisher confirms must be enabled
+    /// on the connection for this to work (enabled by default).
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class)]
+    public class MandatoryAttribute : Attribute
+    {
+    }
+}

Tapeti.Annotations/MessageControllerAttribute.cs

@@ -2,6 +2,11 @@
 
 namespace Tapeti.Annotations
 {
+    /// <inheritdoc />
+    /// <summary>
+    /// Attaching this attribute to a class includes it in the auto-discovery of message controllers
+    /// when using the RegisterAllControllers method. It is not required when manually registering a controller.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Class)]
     public class MessageControllerAttribute : Attribute
     {

Tapeti.Annotations/RequestAttribute.cs

@@ -2,6 +2,14 @@
 
 namespace Tapeti.Annotations
 {
+    /// <inheritdoc />
+    /// <summary>
+    /// Can be attached to a message class to specify that the receiver of the message must
+    /// provide a response message of the type specified in the Response attribute. This response
+    /// must be sent by either returning it from the message handler method or using
+    /// YieldWithResponse when using Tapeti Flow. These methods will respond directly
+    /// to the queue specified in the reply-to header automatically added by Tapeti.
+    /// </summary>
     [AttributeUsage(AttributeTargets.Class)]
     public class RequestAttribute : Attribute
     {

Tapeti.Flow/Default/FlowProvider.cs

@@ -80,7 +80,7 @@ namespace Tapeti.Flow.Default
 
             await context.Store();
 
-            await publisher.Publish(message, properties);
+            await publisher.Publish(message, properties, true);
         }
 
 
@@ -105,9 +105,9 @@ namespace Tapeti.Flow.Default
 
             // TODO disallow if replyto is not specified?
             if (reply.ReplyTo != null)
-                await publisher.PublishDirect(message, reply.ReplyTo, properties);
+                await publisher.PublishDirect(message, reply.ReplyTo, properties, true);
             else
-                await publisher.Publish(message, properties);
+                await publisher.Publish(message, properties, true);
 
             await context.Delete();
         }

Tapeti.Serilog/TapetiSeriLogger.cs

@@ -1,6 +1,8 @@
 using System;
 using ISeriLogger = Serilog.ILogger;
 
+// ReSharper disable UnusedMember.Global
+
 namespace Tapeti.Serilog
 {
     public class TapetiSeriLogger: ILogger

Tapeti/Config/IConfig.cs

@@ -7,6 +7,8 @@ namespace Tapeti.Config
 {
     public interface IConfig
     {
+        bool UsePublisherConfirms { get; }
+
         IDependencyResolver DependencyResolver { get; }
         IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; }
         IReadOnlyList<ICleanupMiddleware> CleanupMiddleware { get; }
@@ -28,6 +30,7 @@ namespace Tapeti.Config
 
     public interface IDynamicQueue : IQueue
     {
+        string GetDeclareQueueName();
         void SetName(string name);
     }
 

Tapeti/Connection/IConnectionEventListener.cs

@@ -1,9 +1,16 @@
 namespace Tapeti.Connection
 {
+    public class DisconnectedEventArgs
+    {
+        public ushort ReplyCode;
+        public string ReplyText;
+    }
+
+
     public interface IConnectionEventListener
     {
         void Connected();
         void Reconnected();
-        void Disconnected();
+        void Disconnected(DisconnectedEventArgs e);
     }
 }

Tapeti/Connection/TapetiPublisher.cs

@@ -1,6 +1,8 @@
 using System;
+using System.Reflection;
 using System.Threading.Tasks;
 using RabbitMQ.Client;
+using Tapeti.Annotations;
 
 namespace Tapeti.Connection
 {
@@ -17,19 +19,25 @@ namespace Tapeti.Connection
 
         public Task Publish(object message)
         {
-            return workerFactory().Publish(message, null);
+            return workerFactory().Publish(message, null, IsMandatory(message));
         }
 
 
-        public Task Publish(object message, IBasicProperties properties)
+        public Task Publish(object message, IBasicProperties properties, bool mandatory)
         {
-            return workerFactory().Publish(message, properties);
+            return workerFactory().Publish(message, properties, mandatory);
         }
 
 
-        public Task PublishDirect(object message, string queueName, IBasicProperties properties)
+        public Task PublishDirect(object message, string queueName, IBasicProperties properties, bool mandatory)
         {
-            return workerFactory().PublishDirect(message, queueName, properties);
+            return workerFactory().PublishDirect(message, queueName, properties, mandatory);
+        }
+
+
+        private static bool IsMandatory(object message)
+        {
+            return message.GetType().GetCustomAttribute<MandatoryAttribute>() != null;
         }
     }
 }

Tapeti/Connection/TapetiSubscriber.cs

@@ -26,6 +26,12 @@ namespace Tapeti.Connection
         }
 
 
+        public Task RebindQueues()
+        {
+            return BindQueues();
+        }
+
+
         public Task Resume()
         {
             if (consuming)

Tapeti/Connection/TapetiWorker.cs

@@ -1,10 +1,14 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using RabbitMQ.Client;
+using RabbitMQ.Client.Events;
 using RabbitMQ.Client.Exceptions;
 using RabbitMQ.Client.Framing;
 using Tapeti.Config;
+using Tapeti.Exceptions;
 using Tapeti.Helpers;
 using Tapeti.Tasks;
 
@@ -13,7 +17,8 @@ namespace Tapeti.Connection
     public class TapetiWorker
     {
         private const int ReconnectDelay = 5000;
-        private const int PublishMaxConnectAttempts = 3;
+        private const int MandatoryReturnTimeout = 30000;
+        private const int MinimumConnectedReconnectDelay = 1000;
 
         private readonly IConfig config;
         private readonly ILogger logger;
@@ -24,8 +29,31 @@ namespace Tapeti.Connection
         private readonly IRoutingKeyStrategy routingKeyStrategy;
         private readonly IExchangeStrategy exchangeStrategy;
         private readonly Lazy<SingleThreadTaskQueue> taskQueue = new Lazy<SingleThreadTaskQueue>();
+
+        
+        // These fields are for use in the taskQueue only!
         private RabbitMQ.Client.IConnection connection;
+        private bool isReconnect;
         private IModel channelInstance;
+        private ulong lastDeliveryTag;
+        private DateTime connectedDateTime;
+        private readonly Dictionary<ulong, ConfirmMessageInfo> confirmMessages = new Dictionary<ulong, ConfirmMessageInfo>();
+        private readonly Dictionary<string, ReturnInfo> returnRoutingKeys = new Dictionary<string, ReturnInfo>();
+
+
+        private class ConfirmMessageInfo
+        {
+            public string ReturnKey;
+            public TaskCompletionSource<int> CompletionSource;
+        }
+
+
+        private class ReturnInfo
+        {
+            public uint RefCount;
+            public int FirstReplyCode;
+        }
+
 
 
         public TapetiWorker(IConfig config)
@@ -39,15 +67,15 @@ namespace Tapeti.Connection
         }
 
 
-        public Task Publish(object message, IBasicProperties properties)
+        public Task Publish(object message, IBasicProperties properties, bool mandatory)
         {
-            return Publish(message, properties, exchangeStrategy.GetExchange(message.GetType()), routingKeyStrategy.GetRoutingKey(message.GetType()));
+            return Publish(message, properties, exchangeStrategy.GetExchange(message.GetType()), routingKeyStrategy.GetRoutingKey(message.GetType()), mandatory);
         }
 
 
-        public Task PublishDirect(object message, string queueName, IBasicProperties properties)
+        public Task PublishDirect(object message, string queueName, IBasicProperties properties, bool mandatory)
         {
-            return Publish(message, properties, "", queueName);
+            return Publish(message, properties, "", queueName, mandatory);
         }
 
 
@@ -56,69 +84,78 @@ namespace Tapeti.Connection
             if (string.IsNullOrEmpty(queueName))
                 throw new ArgumentNullException(nameof(queueName));
 
-            return taskQueue.Value.Add(async () =>
+            return taskQueue.Value.Add(() =>
             {
-                (await GetChannel()).BasicConsume(queueName, false, new TapetiConsumer(this, queueName, config.DependencyResolver, bindings, config.MessageMiddleware, config.CleanupMiddleware));
+                WithRetryableChannel(channel => channel.BasicConsume(queueName, false, new TapetiConsumer(this, queueName, config.DependencyResolver, bindings, config.MessageMiddleware, config.CleanupMiddleware)));
-            }).Unwrap();
+            });
         }
 
 
         public Task Subscribe(IQueue queue)
         {
-            return taskQueue.Value.Add(async () =>
+            return taskQueue.Value.Add(() =>
             {
-                var channel = await GetChannel();
+                WithRetryableChannel(channel => 
-
-                if (queue.Dynamic)
                 {
-                    var dynamicQueue = channel.QueueDeclare(queue.Name);
+                    if (queue.Dynamic)
-                    (queue as IDynamicQueue)?.SetName(dynamicQueue.QueueName);
-
-                    foreach (var binding in queue.Bindings)
                     {
-                        if (binding.QueueBindingMode == QueueBindingMode.RoutingKey)
+                        if (!(queue is IDynamicQueue dynamicQueue))
+                            throw new NullReferenceException("Queue with Dynamic = true must implement IDynamicQueue");
+
+                        var declaredQueue = channel.QueueDeclare(dynamicQueue.GetDeclareQueueName());
+                        dynamicQueue.SetName(declaredQueue.QueueName);
+
+                        foreach (var binding in queue.Bindings)
                         {
-                            var routingKey = routingKeyStrategy.GetRoutingKey(binding.MessageClass);
+                            if (binding.QueueBindingMode == QueueBindingMode.RoutingKey)
-                            var exchange = exchangeStrategy.GetExchange(binding.MessageClass);
+                            {
+                                var routingKey = routingKeyStrategy.GetRoutingKey(binding.MessageClass);
+                                var exchange = exchangeStrategy.GetExchange(binding.MessageClass);
 
-                            channel.QueueBind(dynamicQueue.QueueName, exchange, routingKey);
+                                channel.QueueBind(declaredQueue.QueueName, exchange, routingKey);
+                            }
+
+                            (binding as IBuildBinding)?.SetQueueName(declaredQueue.QueueName);
                         }
-
-                        (binding as IBuildBinding)?.SetQueueName(dynamicQueue.QueueName);
                     }
-                }
+                    else
-                else
-                {
-                    channel.QueueDeclarePassive(queue.Name);
-                    foreach (var binding in queue.Bindings)
                     {
-                        (binding as IBuildBinding)?.SetQueueName(queue.Name);
+                        channel.QueueDeclarePassive(queue.Name);
+                        foreach (var binding in queue.Bindings)
+                        {
+                            (binding as IBuildBinding)?.SetQueueName(queue.Name);
+                        }
                     }
-                }
+                });
-            }).Unwrap();
+            });
         }
 
 
         public Task Respond(ulong deliveryTag, ConsumeResponse response)
         {
-            return taskQueue.Value.Add(async () =>
+            return taskQueue.Value.Add(() =>
             {
+                // No need for a retryable channel here, if the connection is lost we can't
+                // use the deliveryTag anymore.
                 switch (response)
                 {
                     case ConsumeResponse.Ack:
-                        (await GetChannel()).BasicAck(deliveryTag, false);
+                        GetChannel().BasicAck(deliveryTag, false);
                         break;
 
                     case ConsumeResponse.Nack:
-                        (await GetChannel()).BasicNack(deliveryTag, false, false);
+                        GetChannel().BasicNack(deliveryTag, false, false);
                         break;
 
                     case ConsumeResponse.Requeue:
-                        (await GetChannel()).BasicNack(deliveryTag, false, true);
+                        GetChannel().BasicNack(deliveryTag, false, true);
                         break;
+
+                    default:
+                        throw new ArgumentOutOfRangeException(nameof(response), response, null);
                 }
 
-            }).Unwrap();
+            });
         }
 
 
@@ -147,7 +184,7 @@ namespace Tapeti.Connection
         }
 
 
-        private Task Publish(object message, IBasicProperties properties, string exchange, string routingKey)
+        private Task Publish(object message, IBasicProperties properties, string exchange, string routingKey, bool mandatory)
         {
             var context = new PublishContext
             {
@@ -172,22 +209,96 @@ namespace Tapeti.Connection
                 () => taskQueue.Value.Add(async () =>
                 {
                     var body = messageSerializer.Serialize(context.Message, context.Properties);
-                    (await GetChannel(PublishMaxConnectAttempts)).BasicPublish(context.Exchange, context.RoutingKey, false,
+
-                        context.Properties, body);
+                    Task<int> publishResultTask = null;
-                }).Unwrap());
+                    var messageInfo = new ConfirmMessageInfo
+                    {
+                        ReturnKey = GetReturnKey(context.Exchange, context.RoutingKey),
+                        CompletionSource = new TaskCompletionSource<int>()
+                    };
+
+
+                    WithRetryableChannel(channel =>
+                    {
+                        // The delivery tag is lost after a reconnect, register under the new tag
+                        if (config.UsePublisherConfirms)
+                        {
+                            lastDeliveryTag++;
+
+                            confirmMessages.Add(lastDeliveryTag, messageInfo);
+                            publishResultTask = messageInfo.CompletionSource.Task;
+                        }
+                        else
+                            mandatory = false;
+
+                        channel.BasicPublish(context.Exchange, context.RoutingKey, mandatory, context.Properties, body);
+                    });
+
+
+                    if (publishResultTask == null)
+                        return;
+
+                    var delayCancellationTokenSource = new CancellationTokenSource();
+                    var signalledTask = await Task.WhenAny(publishResultTask, Task.Delay(MandatoryReturnTimeout, delayCancellationTokenSource.Token));
+
+                    if (signalledTask != publishResultTask)
+                        throw new TimeoutException($"Timeout while waiting for basic.return for message with class {context.Message?.GetType().FullName ?? "null"} and Id {context.Properties.MessageId}");
+
+                    delayCancellationTokenSource.Cancel();
+
+                    if (publishResultTask.IsCanceled)
+                        throw new NackException($"Mandatory message with class {context.Message?.GetType().FullName ?? "null"} was nacked");
+
+                    var replyCode = publishResultTask.Result;
+
+                    // There is no RabbitMQ.Client.Framing.Constants value for this "No route" reply code
+                    // at the time of writing...
+                    if (replyCode == 312)
+                        throw new NoRouteException($"Mandatory message with class {context.Message?.GetType().FullName ?? "null"} does not have a route");
+
+                    if (replyCode > 0)
+                        throw new NoRouteException($"Mandatory message with class {context.Message?.GetType().FullName ?? "null"} could not be delivery, reply code {replyCode}");
+                }));
             // ReSharper restore ImplicitlyCapturedClosure
         }
 
+
         /// <remarks>
         /// Only call this from a task in the taskQueue to ensure IModel is only used 
         /// by a single thread, as is recommended in the RabbitMQ .NET Client documentation.
         /// </remarks>
-        private async Task<IModel> GetChannel(int? maxAttempts = null)
+        private void WithRetryableChannel(Action<IModel> operation)
         {
-            if (channelInstance != null)
+            while (true)
+            {
+                try
+                {
+                    operation(GetChannel());
+                    break;
+                }
+                catch (AlreadyClosedException e)
+                {
+                    // TODO log?                    
+                }
+            }
+        }
+
+
+        /// <remarks>
+        /// Only call this from a task in the taskQueue to ensure IModel is only used 
+        /// by a single thread, as is recommended in the RabbitMQ .NET Client documentation.
+        /// </remarks>
+        private IModel GetChannel()
+        {
+            if (channelInstance != null && channelInstance.IsOpen)
                 return channelInstance;
 
-            var attempts = 0;
+            // If the Disconnect quickly follows the Connect (when an error occurs that is reported back by RabbitMQ
+            // not related to the connection), wait for a bit to avoid spamming the connection
+            if ((DateTime.UtcNow - connectedDateTime).TotalMilliseconds <= MinimumConnectedReconnectDelay)
+                Thread.Sleep(ReconnectDelay);
+
+
             var connectionFactory = new ConnectionFactory
             {
                 HostName = ConnectionParams.HostName,
@@ -195,7 +306,8 @@ namespace Tapeti.Connection
                 VirtualHost = ConnectionParams.VirtualHost,
                 UserName = ConnectionParams.Username,
                 Password = ConnectionParams.Password,
-                AutomaticRecoveryEnabled = true, // The created connection is an IRecoverable
+                AutomaticRecoveryEnabled = false,
+                TopologyRecoveryEnabled = false,
                 RequestedHeartbeat = 30
             };
 
@@ -208,27 +320,50 @@ namespace Tapeti.Connection
                     connection = connectionFactory.CreateConnection();
                     channelInstance = connection.CreateModel();
 
+                    if (channelInstance == null)
+                        throw new BrokerUnreachableException(null);
+
+                    if (config.UsePublisherConfirms)
+                    {
+                        lastDeliveryTag = 0;
+                        confirmMessages.Clear();
+                        channelInstance.ConfirmSelect();
+                    }
+
                     if (ConnectionParams.PrefetchCount > 0)
                         channelInstance.BasicQos(0, ConnectionParams.PrefetchCount, false);
 
-                    ((IRecoverable)connection).Recovery += (sender, e) => ConnectionEventListener?.Reconnected();
+                    channelInstance.ModelShutdown += (sender, e) =>
+                    {
+                        ConnectionEventListener?.Disconnected(new DisconnectedEventArgs
+                        {
+                            ReplyCode = e.ReplyCode,
+                            ReplyText = e.ReplyText
+                        });
 
-                    channelInstance.ModelShutdown += (sender, e) => ConnectionEventListener?.Disconnected();
+                        channelInstance = null;
+                    };
+
+                    channelInstance.BasicReturn += HandleBasicReturn;
+                    channelInstance.BasicAcks += HandleBasicAck;
+                    channelInstance.BasicNacks += HandleBasicNack;
+
+                    connectedDateTime = DateTime.UtcNow;
+
+                    if (isReconnect)
+                        ConnectionEventListener?.Reconnected();
+                    else
+                        ConnectionEventListener?.Connected();
 
-                    ConnectionEventListener?.Connected();
                     logger.ConnectSuccess(ConnectionParams);
+                    isReconnect = true;
 
                     break;
                 }
                 catch (BrokerUnreachableException e)
                 {
                     logger.ConnectFailed(ConnectionParams, e);
-
+                    Thread.Sleep(ReconnectDelay);
-                    attempts++;
-                    if (maxAttempts.HasValue && attempts > maxAttempts.Value)
-                        throw;
-
-                    await Task.Delay(ReconnectDelay);
                 }
             }
 
@@ -236,6 +371,93 @@ namespace Tapeti.Connection
         }
 
 
+        private void HandleBasicReturn(object sender, BasicReturnEventArgs e)        
+        {
+            /*
+             * "If the message is also published as mandatory, the basic.return is sent to the client before basic.ack."
+             * - https://www.rabbitmq.com/confirms.html
+             *
+             * Because there is no delivery tag included in the basic.return message. This solution is modeled after
+             * user OhJeez' answer on StackOverflow:
+             *
+             * "Since all messages with the same routing key are routed the same way. I assumed that once I get a
+             *  basic.return about a specific routing key, all messages with this routing key can be considered undelivered"
+             * https://stackoverflow.com/questions/21336659/how-to-tell-which-amqp-message-was-not-routed-from-basic-return-response
+             */
+            var key = GetReturnKey(e.Exchange, e.RoutingKey);
+
+            if (!returnRoutingKeys.TryGetValue(key, out var returnInfo))
+            {
+                returnInfo = new ReturnInfo
+                {
+                    RefCount = 0,
+                    FirstReplyCode = e.ReplyCode
+                };
+
+                returnRoutingKeys.Add(key, returnInfo);
+            }
+
+            returnInfo.RefCount++;
+        }
+
+
+        private void HandleBasicAck(object sender, BasicAckEventArgs e)
+        {
+            foreach (var deliveryTag in GetDeliveryTags(e))
+            {
+                if (!confirmMessages.TryGetValue(deliveryTag, out var messageInfo)) 
+                    continue;
+
+                if (returnRoutingKeys.TryGetValue(messageInfo.ReturnKey, out var returnInfo))
+                {
+                    messageInfo.CompletionSource.SetResult(returnInfo.FirstReplyCode);
+
+                    returnInfo.RefCount--;
+                    if (returnInfo.RefCount == 0)
+                        returnRoutingKeys.Remove(messageInfo.ReturnKey);
+                }
+
+                messageInfo.CompletionSource.SetResult(0);
+                confirmMessages.Remove(deliveryTag);
+            }
+        }
+
+
+        private void HandleBasicNack(object sender, BasicNackEventArgs e)
+        {
+            foreach (var deliveryTag in GetDeliveryTags(e))
+            {
+                if (!confirmMessages.TryGetValue(deliveryTag, out var messageInfo)) 
+                    continue;
+
+                messageInfo.CompletionSource.SetCanceled();
+                confirmMessages.Remove(e.DeliveryTag);
+            }
+        }
+
+
+        private IEnumerable<ulong> GetDeliveryTags(BasicAckEventArgs e)
+        {
+            return e.Multiple
+                ? confirmMessages.Keys.Where(tag => tag <= e.DeliveryTag).ToArray()
+                : new[] { e.DeliveryTag };
+        }
+
+
+        private IEnumerable<ulong> GetDeliveryTags(BasicNackEventArgs e)
+        {
+            return e.Multiple
+                ? confirmMessages.Keys.Where(tag => tag <= e.DeliveryTag).ToArray()
+                : new[] { e.DeliveryTag };
+        }
+
+
+        private static string GetReturnKey(string exchange, string routingKey)
+        {
+            return exchange + ':' + routingKey;
+        }
+
+
         private class PublishContext : IPublishContext
         {
             public IDependencyResolver DependencyResolver { get; set; }

Tapeti/Default/ConsoleLogger.cs

@@ -16,7 +16,7 @@ namespace Tapeti.Default
 
         public void ConnectSuccess(TapetiConnectionParams connectionParams)
         {
-            Console.WriteLine($"[Tapeti] Connected");
+            Console.WriteLine("[Tapeti] Connected");
         }
 
         public void HandlerException(Exception e)

Tapeti/Default/FallbackStringEnumConverter.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Diagnostics;
+using Newtonsoft.Json;
+
+namespace Tapeti.Default
+{
+    /// <summary>
+    /// Converts an <see cref="Enum"/> to and from its name string value. If an unknown string value is encountered
+    /// it will translate to 0xDEADBEEF (-559038737) so it can be gracefully handled.
+    /// If you copy this value as-is to another message and try to send it, this converter will throw an exception.
+    ///
+    /// This converter is far simpler than the default StringEnumConverter, it assumes both sides use the same
+    /// enum and therefore skips the naming strategy.
+    /// </summary>
+    public class FallbackStringEnumConverter : JsonConverter
+    {
+        private readonly int invalidEnumValue;
+
+
+        public FallbackStringEnumConverter()
+        {
+            unchecked { invalidEnumValue = (int)0xDEADBEEF; }
+        }
+
+
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            if (value == null)
+            {
+                writer.WriteNull();
+                return;
+            }
+
+            if ((int) value == invalidEnumValue)
+                throw new ArgumentException("Enum value was an unknown string value in an incoming message and can not be published in an outgoing message as-is");
+
+            var outputValue = Enum.GetName(value.GetType(), value);
+            writer.WriteValue(outputValue);
+        }
+
+
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            var isNullable = IsNullableType(objectType);
+
+            if (reader.TokenType == JsonToken.Null)
+            {
+                if (!isNullable)
+                    throw new JsonSerializationException($"Cannot convert null value to {objectType}");
+
+                return null;
+            }
+
+            var actualType = isNullable ? Nullable.GetUnderlyingType(objectType) : objectType;
+            Debug.Assert(actualType != null, nameof(actualType) + " != null");
+
+            if (reader.TokenType != JsonToken.String)
+                throw new JsonSerializationException($"Unexpected token {reader.TokenType} when parsing enum");
+
+            var enumText = reader.Value.ToString();
+            if (enumText == string.Empty && isNullable)
+                return null;
+
+            try
+            {
+                return Enum.Parse(actualType, enumText);
+            }
+            catch (ArgumentException)
+            {
+                return Enum.ToObject(actualType, invalidEnumValue);
+            }
+        }
+
+
+        public override bool CanConvert(Type objectType)
+        {
+            var actualType = IsNullableType(objectType) ? Nullable.GetUnderlyingType(objectType) : objectType;
+            return actualType?.IsEnum ?? false;
+        }
+
+
+        private static bool IsNullableType(Type t)
+        {
+            if (t == null)
+                throw new ArgumentNullException(nameof(t));
+
+            return t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>);
+        }
+    }
+}

Tapeti/Default/JsonMessageSerializer.cs

@@ -3,7 +3,6 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Text;
 using Newtonsoft.Json;
-using Newtonsoft.Json.Converters;
 using RabbitMQ.Client;
 
 namespace Tapeti.Default
@@ -25,7 +24,7 @@ namespace Tapeti.Default
                 NullValueHandling = NullValueHandling.Ignore
             };
 
-            serializerSettings.Converters.Add(new StringEnumConverter());
+            serializerSettings.Converters.Add(new FallbackStringEnumConverter());            
         }
 
 
@@ -52,7 +51,7 @@ namespace Tapeti.Default
                 throw new ArgumentException($"{ClassTypeHeader} header not present");
 
             var messageType = deserializedTypeNames.GetOrAdd(Encoding.UTF8.GetString((byte[])typeName), DeserializeTypeName);
-            return JsonConvert.DeserializeObject(Encoding.UTF8.GetString(body), messageType);
+            return JsonConvert.DeserializeObject(Encoding.UTF8.GetString(body), messageType, serializerSettings);
         }
 
 

Tapeti/Default/PublishResultBinding.cs

@@ -3,6 +3,7 @@ using System.Diagnostics;
 using System.Reflection;
 using System.Threading.Tasks;
 using RabbitMQ.Client.Framing;
+using Tapeti.Annotations;
 using Tapeti.Config;
 using Tapeti.Helpers;
 
@@ -18,23 +19,30 @@ namespace Tapeti.Default
                 return;
 
 
-            if (!context.Result.Info.ParameterType.IsTypeOrTaskOf(t => t.IsClass, out var isTaskOf, out var actualType))
+            var hasClassResult = context.Result.Info.ParameterType.IsTypeOrTaskOf(t => t.IsClass, out var isTaskOf, out var actualType);
+            
+            var request = context.MessageClass?.GetCustomAttribute<RequestAttribute>();
+            var expectedClassResult = request?.Response;
+
+            // Verify the return type matches with the Request attribute of the message class. This is a backwards incompatible change in
+            // Tapeti 1.2: if you just want to publish another message as a result of the incoming message, explicitly call IPublisher.Publish.
+            if (!hasClassResult && expectedClassResult != null || hasClassResult && expectedClassResult != actualType)
+               throw new ArgumentException($"Message handler must return type {expectedClassResult?.FullName ?? "void"} in controller {context.Method.DeclaringType?.FullName}, method {context.Method.Name}, found: {actualType?.FullName ?? "void"}");
+
+            if (!hasClassResult)
                 return;
 
 
+
             if (isTaskOf)
             {
                 var handler = GetType().GetMethod("PublishGenericTaskResult", BindingFlags.NonPublic | BindingFlags.Static)?.MakeGenericMethod(actualType);
                 Debug.Assert(handler != null, nameof(handler) + " != null");
 
-                context.Result.SetHandler(async (messageContext, value) =>
+                context.Result.SetHandler(async (messageContext, value) => { await (Task) handler.Invoke(null, new[] {messageContext, value }); });
-                {
-                    await (Task)handler.Invoke(null, new[] { messageContext, value });
-                });
             }
             else
-                context.Result.SetHandler((messageContext, value) => 
+                context.Result.SetHandler((messageContext, value) => Reply(value, messageContext));
-                    value == null ? null : Reply(value, messageContext));
         }
 
 
@@ -43,13 +51,15 @@ namespace Tapeti.Default
         private static async Task PublishGenericTaskResult<T>(IMessageContext messageContext, object value) where T : class
         {
             var message = await (Task<T>)value;
-            if (message != null)
+            await Reply(message, messageContext);
-                await Reply(message, messageContext);
         }
 
 
         private static Task Reply(object message, IMessageContext messageContext)
         {
+            if (message == null)
+                throw new ArgumentException("Return value of a request message handler must not be null");
+
             var publisher = (IInternalPublisher)messageContext.DependencyResolver.Resolve<IPublisher>();
             var properties = new BasicProperties();
 
@@ -59,9 +69,9 @@ namespace Tapeti.Default
                 properties.CorrelationId = messageContext.Properties.CorrelationId;
 
             if (messageContext.Properties.IsReplyToPresent())
-                return publisher.PublishDirect(message, messageContext.Properties.ReplyTo, properties);
+                return publisher.PublishDirect(message, messageContext.Properties.ReplyTo, properties, true);
 
-            return publisher.Publish(message, properties);
+            return publisher.Publish(message, properties, false);
         }
     }
 }

Tapeti/Exceptions/NackException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Tapeti.Exceptions
+{
+    public class NackException : Exception
+    {
+        public NackException(string message) : base(message) { }
+    }
+}

Tapeti/Exceptions/NoRouteException.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Tapeti.Exceptions
+{
+    public class NoRouteException : Exception
+    {
+        public NoRouteException(string message) : base(message) { }
+    }
+}

Tapeti/IPublisher.cs

@@ -13,7 +13,7 @@ namespace Tapeti
 
     public interface IInternalPublisher : IPublisher
     {
-        Task Publish(object message, IBasicProperties properties);
+        Task Publish(object message, IBasicProperties properties, bool mandatory);
-        Task PublishDirect(object message, string queueName, IBasicProperties properties);
+        Task PublishDirect(object message, string queueName, IBasicProperties properties, bool mandatory);
     }
 }

Tapeti/TapetiConfig.cs

@@ -8,6 +8,7 @@ using Tapeti.Config;
 using Tapeti.Default;
 using Tapeti.Helpers;
 
+// ReSharper disable UnusedMember.Global
 
 namespace Tapeti
 {
@@ -31,6 +32,8 @@ namespace Tapeti
 
         private readonly IDependencyResolver dependencyResolver;
 
+        private bool usePublisherConfirms = true;
+
 
         public TapetiConfig(IDependencyResolver dependencyResolver)
         {
@@ -90,7 +93,16 @@ namespace Tapeti
                 queues.AddRange(dynamicBindings.Select(bl => new Queue(new QueueInfo { Dynamic = true, Name = GetDynamicQueueName(prefixGroup.Key) }, bl)));
             }
 
-            var config = new Config(dependencyResolver, messageMiddleware, cleanupMiddleware, publishMiddleware, queues);
+            var config = new Config(queues)
+            {
+                DependencyResolver = dependencyResolver, 
+                MessageMiddleware = messageMiddleware, 
+                CleanupMiddleware = cleanupMiddleware, 
+                PublishMiddleware = publishMiddleware,
+
+                UsePublisherConfirms = usePublisherConfirms
+            };
+
             (dependencyResolver as IDependencyContainer)?.RegisterDefaultSingleton<IConfig>(config);
 
             return config;
@@ -154,11 +166,34 @@ namespace Tapeti
             return this;
         }
 
+        
+        /// <summary>
+        /// WARNING: disabling publisher confirms means there is no guarantee that a Publish succeeds,
+        /// and disables Tapeti.Flow from verifying if a request/response can be routed. This may
+        /// result in never-ending flows. Only disable if you can accept those consequences.
+        /// </summary>
+        public TapetiConfig DisablePublisherConfirms()
+        {
+            usePublisherConfirms = false;
+            return this;
+        }
+
+
+        /// <summary>
+        /// WARNING: disabling publisher confirms means there is no guarantee that a Publish succeeds,
+        /// and disables Tapeti.Flow from verifying if a request/response can be routed. This may
+        /// result in never-ending flows. Only disable if you accept those consequences.
+        /// </summary>
+        public TapetiConfig SetPublisherConfirms(bool enabled)
+        {
+            usePublisherConfirms = enabled;
+            return this;
+        }
+
 
         public void RegisterDefaults()
         {
-            var container = dependencyResolver as IDependencyContainer;
+            if (!(dependencyResolver is IDependencyContainer container))
-            if (container == null)
                 return;
 
             if (ConsoleHelper.IsAvailable())
@@ -399,21 +434,19 @@ namespace Tapeti
 
         protected class Config : IConfig
         {
-            public IDependencyResolver DependencyResolver { get; }
+            public bool UsePublisherConfirms { get; set; }
-            public IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; }
+
-            public IReadOnlyList<ICleanupMiddleware> CleanupMiddleware { get; }
+            public IDependencyResolver DependencyResolver { get; set; }
-            public IReadOnlyList<IPublishMiddleware> PublishMiddleware { get; }
+            public IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; set; }
+            public IReadOnlyList<ICleanupMiddleware> CleanupMiddleware { get; set; }
+            public IReadOnlyList<IPublishMiddleware> PublishMiddleware { get; set; }
             public IEnumerable<IQueue> Queues { get; }
 
             private readonly Dictionary<MethodInfo, IBinding> bindingMethodLookup;
 
 
-            public Config(IDependencyResolver dependencyResolver, IReadOnlyList<IMessageMiddleware> messageMiddleware, IReadOnlyList<ICleanupMiddleware> cleanupMiddleware, IReadOnlyList<IPublishMiddleware> publishMiddleware, IEnumerable<IQueue> queues)
+            public Config(IEnumerable<IQueue> queues)
             {
-                DependencyResolver = dependencyResolver;
-                MessageMiddleware = messageMiddleware;
-                CleanupMiddleware = cleanupMiddleware;
-                PublishMiddleware = publishMiddleware;
                 Queues = queues.ToList();
 
                 bindingMethodLookup = Queues.SelectMany(q => q.Bindings).ToDictionary(b => b.Method, b => b);
@@ -429,6 +462,8 @@ namespace Tapeti
 
         protected class Queue : IDynamicQueue
         {
+            private readonly string declareQueueName;
+
             public bool Dynamic { get; }
             public string Name { get; set;  }
             public IEnumerable<IBinding> Bindings { get; }
@@ -436,12 +471,20 @@ namespace Tapeti
 
             public Queue(QueueInfo queue, IEnumerable<IBinding> bindings)
             {
+                declareQueueName = queue.Name;
+
                 Dynamic = queue.Dynamic.GetValueOrDefault();
                 Name = queue.Name;
                 Bindings = bindings;
             }
 
 
+            public string GetDeclareQueueName()
+            {
+                return declareQueueName;
+            }
+
+
             public void SetName(string name)
             {
                 Name = name;

Tapeti/TapetiConnection.cs

@@ -8,13 +8,15 @@ using Tapeti.Connection;
 
 namespace Tapeti
 {
+    public delegate void DisconnectedEventHandler(object sender, DisconnectedEventArgs e);
+
     public class TapetiConnection : IDisposable
     {
         private readonly IConfig config;
         public TapetiConnectionParams Params { get; set; }
 
         private readonly Lazy<TapetiWorker> worker;
-
+        private TapetiSubscriber subscriber;
 
         public TapetiConnection(IConfig config)
         {
@@ -29,15 +31,17 @@ namespace Tapeti
         }
 
         public event EventHandler Connected;
-
+        public event DisconnectedEventHandler Disconnected;
-        public event EventHandler Disconnected;
-
         public event EventHandler Reconnected;
 
+
         public async Task<ISubscriber> Subscribe(bool startConsuming = true)
         {
-            var subscriber = new TapetiSubscriber(() => worker.Value, config.Queues.ToList());
+            if (subscriber == null)
-            await subscriber.BindQueues();
+            {
+                subscriber = new TapetiSubscriber(() => worker.Value, config.Queues.ToList());
+                await subscriber.BindQueues();
+            }
 
             if (startConsuming)
                 await subscriber.Resume();
@@ -46,9 +50,9 @@ namespace Tapeti
         }
 
 
-        public ISubscriber SubscribeSync()
+        public ISubscriber SubscribeSync(bool startConsuming = true)
         {
-            return Subscribe().Result;
+            return Subscribe(startConsuming).Result;
         }
 
 
@@ -84,9 +88,9 @@ namespace Tapeti
                 owner.OnConnected(new EventArgs());
             }
 
-            public void Disconnected()
+            public void Disconnected(DisconnectedEventArgs e)
             {
-                owner.OnDisconnected(new EventArgs());
+                owner.OnDisconnected(e);
             }
 
             public void Reconnected()
@@ -97,17 +101,23 @@ namespace Tapeti
 
         protected virtual void OnConnected(EventArgs e)
         {
-            Connected?.Invoke(this, e);
+            Task.Run(() => Connected?.Invoke(this, e));
         }
 
         protected virtual void OnReconnected(EventArgs e)
         {
-            Reconnected?.Invoke(this, e);
+            Task.Run(() =>
+            {
+                subscriber?.RebindQueues().ContinueWith((t) =>
+                {
+                    Reconnected?.Invoke(this, e);
+                });
+            });
         }
 
-        protected virtual void OnDisconnected(EventArgs e)
+        protected virtual void OnDisconnected(DisconnectedEventArgs e)
         {
-            Disconnected?.Invoke(this, e);
+            Task.Run(() => Disconnected?.Invoke(this, e));
         }
     }
 }

Tapeti/Tasks/SingleThreadTaskQueue.cs

@@ -27,7 +27,7 @@ namespace Tapeti.Tasks
         }
 
 
-        public Task<T> Add<T>(Func<T> func)
+        public Task Add(Func<Task> func)
         {
             lock (previousTaskLock)
             {
@@ -36,7 +36,11 @@ namespace Tapeti.Tasks
                     , singleThreadScheduler.Value);
 
                 previousTask = task;
-                return task;
+
+                // 'task' completes at the moment a Task is returned (for example, an await is encountered),
+                // this is used to chain the next. We return the unwrapped Task however, so that the caller
+                // awaits until the full task chain has completed.
+                return task.Unwrap();
             }
         }
 

Test/MarcoController.cs

@@ -80,12 +80,16 @@ namespace Test
             return flowProvider.YieldWithParallelRequest()
                 .AddRequestSync<PoloConfirmationRequestMessage, PoloConfirmationResponseMessage>(new PoloConfirmationRequestMessage
                 {
-                    StoredInState = StateTestGuid
+                    StoredInState = StateTestGuid,
+                    EnumValue = TestEnum.Value1,
+
                 }, HandlePoloConfirmationResponse1)
 
                 .AddRequestSync<PoloConfirmationRequestMessage, PoloConfirmationResponseMessage>(new PoloConfirmationRequestMessage
                 {
-                    StoredInState = StateTestGuid
+                    StoredInState = StateTestGuid,
+                    EnumValue = TestEnum.Value2,
+                    OptionalEnumValue = TestEnum.Value1
                 }, HandlePoloConfirmationResponse2)
 
                 .YieldSync(ContinuePoloConfirmation);
@@ -127,7 +131,9 @@ namespace Test
 
             return new PoloConfirmationResponseMessage
             {
-                ShouldMatchState = message.StoredInState
+                ShouldMatchState = message.StoredInState,
+                EnumValue = message.EnumValue,
+                OptionalEnumValue = message.OptionalEnumValue
             };
         }
 
@@ -141,6 +147,13 @@ namespace Test
     }
 
 
+    public enum TestEnum
+    {
+        Value1,
+        Value2
+    }
+
+
     [Request(Response = typeof(PoloMessage))]
     public class MarcoMessage
     {
@@ -157,6 +170,9 @@ namespace Test
     {
         [Required]
         public Guid StoredInState { get; set; }
+
+        public TestEnum EnumValue;
+        public TestEnum? OptionalEnumValue;
     }
 
 
@@ -164,5 +180,8 @@ namespace Test
     {
         [Required]
         public Guid ShouldMatchState { get; set; }
+
+        public TestEnum EnumValue;
+        public TestEnum? OptionalEnumValue;
     }
 }

Test/MyLogger.cs

@@ -1,25 +0,0 @@
-using System;
-using Tapeti;
-
-namespace Test
-{
-    public class MyLogger : ILogger
-    {
-        public void Connect(TapetiConnectionParams connectionParams)
-        {
-        }
-
-        public void ConnectFailed(TapetiConnectionParams connectionParams, Exception exception)
-        {
-        }
-
-        public void ConnectSuccess(TapetiConnectionParams connectionParams)
-        {
-        }
-
-        public void HandlerException(Exception e)
-        {
-            Console.WriteLine("Mylogger: " + e.Message);
-        }
-    }
-}

Test/Program.cs

@@ -5,7 +5,6 @@ using Tapeti.DataAnnotations;
 using Tapeti.Flow;
 using Tapeti.SimpleInjector;
 using System.Threading;
-using Tapeti.Flow.SQL;
 
 namespace Test
 {
@@ -14,58 +13,60 @@ namespace Test
         private static void Main()
         {
             // TODO logging
-
+            try
-            var container = new Container();
-            container.Register<MarcoEmitter>();
-            container.Register<Visualizer>();
-            container.Register<ILogger, Tapeti.Default.ConsoleLogger>();
-
-            var config = new TapetiConfig(new SimpleInjectorDependencyResolver(container))
-                //.WithFlowSqlRepository("Server=localhost;Database=TapetiTest;Integrated Security=true")
-                .WithFlow()
-                .WithDataAnnotations()
-                .RegisterAllControllers()
-                .Build();
-
-            using (var connection = new TapetiConnection(config)
             {
-                Params = new TapetiAppSettingsConnectionParams()
+                var container = new Container();
-            })
+                container.Register<MarcoEmitter>();
+                container.Register<Visualizer>();
+                container.Register<ILogger, Tapeti.Default.ConsoleLogger>();
+
+                var config = new TapetiConfig(new SimpleInjectorDependencyResolver(container))
+                    //.WithFlowSqlRepository("Server=localhost;Database=TapetiTest;Integrated Security=true")
+                    .WithFlow()
+                    .WithDataAnnotations()
+                    .RegisterAllControllers()
+                    //.DisablePublisherConfirms() -> you probably never want to do this if you're using Flow or want requeues when a publish fails
+                    .Build();
+
+                using (var connection = new TapetiConnection(config)
+                {
+                    Params = new TapetiAppSettingsConnectionParams()
+                })
+                {
+                    var flowStore = container.GetInstance<IFlowStore>();
+                    var flowStore2 = container.GetInstance<IFlowStore>();
+
+                    Console.WriteLine("IFlowHandler is singleton = " + (flowStore == flowStore2));
+
+                    connection.Connected += (sender, e) => { Console.WriteLine("Event Connected"); };
+                    connection.Disconnected += (sender, e) => { Console.WriteLine("Event Disconnected"); };
+                    connection.Reconnected += (sender, e) => { Console.WriteLine("Event Reconnected"); };
+
+                    Console.WriteLine("Subscribing...");
+                    var subscriber = connection.Subscribe(false).Result;
+
+                    Console.WriteLine("Consuming...");
+                    subscriber.Resume().Wait();
+
+                    Console.WriteLine("Done!");
+
+                    connection.GetPublisher().Publish(new FlowEndController.PingMessage());
+
+                    //container.GetInstance<IFlowStarter>().Start<MarcoController, bool>(c => c.StartFlow, true).Wait();
+                    container.GetInstance<IFlowStarter>().Start<MarcoController>(c => c.TestParallelRequest).Wait();
+
+                    Thread.Sleep(1000);
+
+                    var emitter = container.GetInstance<MarcoEmitter>();
+                    emitter.Run().Wait();
+
+
+                }
+            }
+            catch (Exception e)
             {
-                var flowStore = container.GetInstance<IFlowStore>();
+                Console.WriteLine(e.ToString());
-                var flowStore2 = container.GetInstance<IFlowStore>();
+                Console.ReadKey();
-
-                Console.WriteLine("IFlowHandler is singleton = " + (flowStore == flowStore2));
-
-                connection.Connected += (sender, e) => {
-                    Console.WriteLine("Event Connected");
-                };
-                connection.Disconnected += (sender, e) => {
-                    Console.WriteLine("Event Disconnected");
-                };
-                connection.Reconnected += (sender, e) => {
-                    Console.WriteLine("Event Reconnected");
-                };
-
-                Console.WriteLine("Subscribing...");
-                var subscriber = connection.Subscribe(false).Result;
-
-                Console.WriteLine("Consuming...");
-                subscriber.Resume().Wait();
-
-                Console.WriteLine("Done!");
-
-                connection.GetPublisher().Publish(new FlowEndController.PingMessage());
-
-                //container.GetInstance<IFlowStarter>().Start<MarcoController, bool>(c => c.StartFlow, true);
-                container.GetInstance<IFlowStarter>().Start<MarcoController>(c => c.TestParallelRequest);
-
-                Thread.Sleep(1000);
-
-                var emitter = container.GetInstance<MarcoEmitter>();
-                emitter.Run().Wait();
-
-
             }
         }
     }