First working prototype of the flow port

.gitignore

@@ -2,3 +2,4 @@
 bin/
 obj/
 packages/
+*.user

Config/IConfig.cs

@@ -7,7 +7,7 @@ namespace Tapeti.Config
 {
     public interface IConfig
     {
-        string Exchange { get; }
+        string SubscribeExchange { get; }
         IDependencyResolver DependencyResolver { get; }
         IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; }
         IEnumerable<IQueue> Queues { get; }
@@ -33,9 +33,10 @@ namespace Tapeti.Config
         string QueueName { get; }
 
         IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; }
+        IReadOnlyList<IBindingFilter> BindingFilters { get; }
 
-        bool Accept(object message);
+        Task<bool> Accept(IMessageContext context, object message);
-        Task<object> Invoke(IMessageContext context, object message);
+        Task Invoke(IMessageContext context, object message);
     }
 
 

Config/IMessageContext.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Reflection;
 using RabbitMQ.Client;
 
 namespace Tapeti.Config
@@ -19,5 +20,10 @@ namespace Tapeti.Config
         /// Controller will be null when passed to an IBindingFilter
         /// </summary>
         object Controller { get; }
+
+        /// <summary>
+        /// Binding will be null when passed to an IBindingFilter
+        /// </summary>
+        IBinding Binding { get; }
     }
 }

Connection/TapetiConsumer.cs

@@ -36,37 +36,36 @@ namespace Tapeti.Connection
                     throw new ArgumentException("Empty message");
 
                 var validMessageType = false;
-                foreach (var binding in bindings.Where(b => b.Accept(message)))
+
+                using (var context = new MessageContext
                 {
-                    using (var context = new MessageContext
+                    DependencyResolver = dependencyResolver,
-                    {
+                    Queue = queueName,
-                        DependencyResolver = dependencyResolver,
+                    RoutingKey = routingKey,
-                        Controller = dependencyResolver.Resolve(binding.Controller),
+                    Message = message,
-                        Queue = queueName,
+                    Properties = properties
-                        RoutingKey = routingKey,
+                })
-                        Message = message,
+                {
-                        Properties = properties
+                    foreach (var binding in bindings)
-                    })
                     {
+                        if (!binding.Accept(context, message).Result)
+                            continue;
+
+                        context.Controller = dependencyResolver.Resolve(binding.Controller);
+                        context.Binding = binding;
+
                         // ReSharper disable AccessToDisposedClosure - MiddlewareHelper will not keep a reference to the lambdas
                         MiddlewareHelper.GoAsync(
                             binding.MessageMiddleware != null
                                 ? messageMiddleware.Concat(binding.MessageMiddleware).ToList()
                                 : messageMiddleware,
                             async (handler, next) => await handler.Handle(context, next),
-                            async () =>
+                            () => binding.Invoke(context, message)
-                            {
-                                var result = binding.Invoke(context, message).Result;
-
-                                // TODO change to result handler
-                                if (result != null)
-                                    await worker.Publish(result, null);
-                            }
                         ).Wait();
                         // ReSharper restore AccessToDisposedClosure
-                    }
 
-                    validMessageType = true;
+                        validMessageType = true;
+                    }
                 }
 
                 if (!validMessageType)
@@ -74,9 +73,15 @@ namespace Tapeti.Connection
 
                 worker.Respond(deliveryTag, ConsumeResponse.Ack);
             }
-            catch (Exception)
+            catch (Exception e)
             {
+                // TODO allow different exception handling depending on exception type
                 worker.Respond(deliveryTag, ConsumeResponse.Requeue);
+
+                var aggregateException = e as AggregateException;
+                if (aggregateException != null && aggregateException.InnerExceptions.Count == 1)
+                    throw aggregateException.InnerExceptions[0];
+
                 throw;
             }
         }
@@ -87,6 +92,7 @@ namespace Tapeti.Connection
             public IDependencyResolver DependencyResolver { get; set; }
 
             public object Controller { get; set; }
+            public IBinding Binding { get; set; }
 
             public string Queue { get; set; }
             public string RoutingKey { get; set; }

Connection/TapetiPublisher.cs

@@ -4,7 +4,7 @@ using RabbitMQ.Client;
 
 namespace Tapeti.Connection
 {
-    public class TapetiPublisher : IAdvancedPublisher
+    public class TapetiPublisher : IInternalPublisher
     {
         private readonly Func<TapetiWorker> workerFactory;
 

Connection/TapetiWorker.cs

@@ -12,7 +12,7 @@ namespace Tapeti.Connection
     public class TapetiWorker
     {
         public TapetiConnectionParams ConnectionParams { get; set; }
-        public string Exchange { get; set; }
+        public string SubscribeExchange { get; set; }
 
         private readonly IDependencyResolver dependencyResolver;
         private readonly IReadOnlyList<IMessageMiddleware> messageMiddleware;
@@ -34,7 +34,8 @@ namespace Tapeti.Connection
 
         public Task Publish(object message, IBasicProperties properties)
         {
-            return Publish(message, properties, Exchange, routingKeyStrategy.GetRoutingKey(message.GetType()));
+            // TODO use exchange strategy!
+            return Publish(message, properties, SubscribeExchange, routingKeyStrategy.GetRoutingKey(message.GetType()));
         }
 
 
@@ -66,7 +67,7 @@ namespace Tapeti.Connection
                     foreach (var binding in queue.Bindings)
                     {
                         var routingKey = routingKeyStrategy.GetRoutingKey(binding.MessageClass);
-                        channel.QueueBind(dynamicQueue.QueueName, Exchange, routingKey);
+                        channel.QueueBind(dynamicQueue.QueueName, SubscribeExchange, routingKey);
 
                         (binding as IDynamicQueueBinding)?.SetQueueName(dynamicQueue.QueueName);
                     }
@@ -173,6 +174,9 @@ namespace Tapeti.Connection
                     connection = connectionFactory.CreateConnection();
                     channelInstance = connection.CreateModel();
 
+                    if (ConnectionParams.PrefetchCount > 0)
+                        channelInstance.BasicQos(0, ConnectionParams.PrefetchCount, false);
+
                     break;
                 }
                 catch (BrokerUnreachableException)

Default/NamespaceMatchExchangeStrategy.cs

@@ -10,9 +10,9 @@ namespace Tapeti.Default
         private readonly Regex namespaceRegEx;
 
 
-        public NamespaceMatchExchangeStrategy(string namespaceFormat = DefaultFormat)
+        public NamespaceMatchExchangeStrategy()
         {
-            namespaceRegEx = new Regex(namespaceFormat, RegexOptions.Compiled | RegexOptions.Singleline);
+            namespaceRegEx = new Regex(DefaultFormat, RegexOptions.Compiled | RegexOptions.Singleline);
         }
 
 

Default/PublishResultBinding.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Threading.Tasks;
+using RabbitMQ.Client.Framing;
+using Tapeti.Config;
+using Tapeti.Helpers;
+
+namespace Tapeti.Default
+{
+    public class PublishResultBinding : IBindingMiddleware
+    {
+        public void Handle(IBindingContext context, Action next)
+        {
+            next();
+
+            if (context.Result.HasHandler)
+                return;
+
+            bool isTask;
+            if (context.Result.Info.ParameterType.IsTypeOrTaskOf(t => t.IsClass, out isTask))
+            {
+                if (isTask)
+                {
+                    context.Result.SetHandler(async (messageContext, value) =>
+                    {
+                        var message = await (Task<object>)value;
+                        if (message != null)
+                            await Reply(message, messageContext);
+                    });
+                }
+                else
+                    context.Result.SetHandler((messageContext, value) => 
+                        value == null ? null : Reply(value, messageContext));
+            }
+        }
+
+
+        private Task Reply(object message, IMessageContext messageContext)
+        {
+            var publisher = (IInternalPublisher)messageContext.DependencyResolver.Resolve<IPublisher>();
+            var properties = new BasicProperties();
+
+            // Only set the property if it's not null, otherwise a string reference exception can occur:
+            // http://rabbitmq.1065348.n5.nabble.com/SocketException-when-invoking-model-BasicPublish-td36330.html
+            if (messageContext.Properties.IsCorrelationIdPresent())
+                properties.CorrelationId = messageContext.Properties.CorrelationId;
+
+            if (messageContext.Properties.IsReplyToPresent())
+                return publisher.PublishDirect(message, messageContext.Properties.ReplyTo, properties);
+
+            return publisher.Publish(message, properties);
+        }
+    }
+}

Helpers/MiddlewareHelper.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.Eventing.Reader;
 using System.Threading.Tasks;
 
 namespace Tapeti.Helpers

Helpers/TaskTypeHelper.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Tapeti.Helpers
+{
+    public static class TaskTypeHelper
+    {
+        public static bool IsTypeOrTaskOf(this Type type, Func<Type, bool> predicate, out bool isTask)
+        {
+            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Task<>))
+            {
+                isTask = true;
+
+                var genericArguments = type.GetGenericArguments();
+                return genericArguments.Length == 1 && predicate(genericArguments[0]);
+            }
+
+            isTask = false;
+            return predicate(type);
+        }
+
+
+        public static bool IsTypeOrTaskOf(this Type type, Type compareTo, out bool isTask)
+        {
+            return IsTypeOrTaskOf(type, t => t == compareTo, out isTask);
+        }
+    }
+}

IDependencyResolver.cs

@@ -1,5 +1,4 @@
 using System;
-using Tapeti.Config;
 
 namespace Tapeti
 {
@@ -13,8 +12,12 @@ namespace Tapeti
     public interface IDependencyContainer : IDependencyResolver
     {
         void RegisterDefault<TService, TImplementation>() where TService : class where TImplementation : class, TService;
-        void RegisterPublisher(Func<IPublisher> publisher);
+        void RegisterDefault<TService>(Func<TService> factory) where TService : class;
-        void RegisterConfig(IConfig config);
+
+        void RegisterDefaultSingleton<TService, TImplementation>() where TService : class where TImplementation : class, TService;
+        void RegisterDefaultSingleton<TService>(TService instance) where TService : class;
+        void RegisterDefaultSingleton<TService>(Func<TService> factory) where TService : class;
+
         void RegisterController(Type type);
     }
 }

IPublisher.cs

@@ -3,13 +3,15 @@ using RabbitMQ.Client;
 
 namespace Tapeti
 {
+    // Note: Tapeti assumes every implementation of IPublisher can also be cast to an IInternalPublisher.
+    // The distinction is made on purpose to trigger code-smells in non-Tapeti code when casting.
     public interface IPublisher
     {
         Task Publish(object message);
     }
 
 
-    public interface IAdvancedPublisher : IPublisher
+    public interface IInternalPublisher : IPublisher
     {
         Task Publish(object message, IBasicProperties properties);
         Task PublishDirect(object message, string queueName, IBasicProperties properties);

Properties/AssemblyInfo.cs

@@ -7,9 +7,9 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTitle("Tapeti")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("Hewlett-Packard Company")]
+[assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("Tapeti")]
-[assembly: AssemblyCopyright("Copyright © Hewlett-Packard Company 2016")]
+[assembly: AssemblyCopyright("")]
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 

Tapeti.Flow/ConfigExtensions.cs

@@ -0,0 +1,11 @@
+namespace Tapeti.Flow
+{
+    public static class ConfigExtensions
+    {
+        public static TapetiConfig WithFlow(this TapetiConfig config)
+        {
+            config.Use(new FlowMiddleware());
+            return config;
+        }
+    }
+}

Tapeti.Flow/Default/FlowBindingFilter.cs

@@ -10,14 +10,10 @@ namespace Tapeti.Flow.Default
         public async Task<bool> Accept(IMessageContext context, IBinding binding)
         {
             var flowContext = await GetFlowContext(context);
-            if (flowContext?.FlowState == null)
+            if (flowContext?.ContinuationMetadata == null)
                 return false;
 
-            string continuation;
+            return flowContext.ContinuationMetadata.MethodName == MethodSerializer.Serialize(binding.Method);
-            if (!flowContext.FlowState.Continuations.TryGetValue(flowContext.ContinuationID, out continuation))
-                return false;
-
-            return continuation == MethodSerializer.Serialize(binding.Method);
         }
 
 
@@ -35,27 +31,29 @@ namespace Tapeti.Flow.Default
 
             var flowStore = context.DependencyResolver.Resolve<IFlowStore>();
 
-            var flowStateID = await flowStore.FindFlowStateID(continuationID);
+            var flowID = await flowStore.FindFlowID(continuationID);
-            if (!flowStateID.HasValue)
+            if (!flowID.HasValue)
                 return null;
 
-            var flowStateLock = await flowStore.LockFlowState(flowStateID.Value);
+            var flowStateLock = await flowStore.LockFlowState(flowID.Value);
             if (flowStateLock == null)
                 return null;
 
             var flowState = await flowStateLock.GetFlowState();
+            if (flowState == null)
+                return null;
 
-
+            ContinuationMetadata continuation;
-            var flowMetadata = flowState != null ? Newtonsoft.Json.JsonConvert.DeserializeObject<FlowMetadata>(flowState.Metadata) : null;
-            //var continuationMetaData = Newtonsoft.Json.JsonConvert.DeserializeObject<ContinuationMetadata>(continuation.MetaData);
 
             var flowContext = new FlowContext
             {
                 MessageContext = context,
-                ContinuationID = continuationID,
+
                 FlowStateLock = flowStateLock,
                 FlowState = flowState,
-                Reply = flowMetadata?.Reply
+
+                ContinuationID = continuationID,
+                ContinuationMetadata = flowState.Continuations.TryGetValue(continuationID, out continuation) ? continuation : null
             };
 
             // IDisposable items in the IMessageContext are automatically disposed

Tapeti.Flow/Default/FlowContext.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Tapeti.Config;
 
 namespace Tapeti.Flow.Default
@@ -8,37 +9,13 @@ namespace Tapeti.Flow.Default
         public IMessageContext MessageContext { get; set; }
         public IFlowStateLock FlowStateLock { get; set; }
         public FlowState FlowState { get; set; }
+
         public Guid ContinuationID { get; set; }
-
+        public ContinuationMetadata ContinuationMetadata { get; set; }
-        public FlowReplyMetadata Reply { get; set; }
-
 
         public void Dispose()
         {
-            MessageContext?.Dispose();
             FlowStateLock?.Dispose();
         }
     }
-
-
-    internal class FlowReplyMetadata
-    {
-        public string ReplyTo { get; set; }
-        public string CorrelationId { get; set; }
-        public string ResponseTypeName { get; set; }
-    }
-
-
-    internal class FlowMetadata
-    {
-        public string ControllerTypeName { get; set; }
-        public FlowReplyMetadata Reply { get; set; }
-    }
-
-
-    internal class ContinuationMetadata
-    {
-        public string MethodName { get; set; }
-        public string ConvergeMethodName { get; set; }
-    }
 }

Tapeti.Flow/Default/FlowMessageMiddleware.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Threading.Tasks;
 using Tapeti.Config;
-using Tapeti.Flow.FlowHelpers;
 
 namespace Tapeti.Flow.Default
 {

Tapeti.Flow/Default/FlowProvider.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Reflection;
 using System.Threading.Tasks;
 using RabbitMQ.Client.Framing;
@@ -11,13 +12,13 @@ namespace Tapeti.Flow.Default
     public class FlowProvider : IFlowProvider, IFlowHandler
     {
         private readonly IConfig config;
-        private readonly IAdvancedPublisher publisher;
+        private readonly IInternalPublisher publisher;
 
 
         public FlowProvider(IConfig config, IPublisher publisher)
         {
             this.config = config;
-            this.publisher = (IAdvancedPublisher)publisher;
+            this.publisher = (IInternalPublisher)publisher;
         }
 
 
@@ -55,11 +56,11 @@ namespace Tapeti.Flow.Default
             var continuationID = Guid.NewGuid();
 
             context.FlowState.Continuations.Add(continuationID,
-                Newtonsoft.Json.JsonConvert.SerializeObject(new ContinuationMetadata
+                new ContinuationMetadata
                 {
                     MethodName = responseHandlerInfo.MethodName,
                     ConvergeMethodName = null
-                }));
+                });
 
             var properties = new BasicProperties
             {
@@ -73,25 +74,32 @@ namespace Tapeti.Flow.Default
 
         private async Task SendResponse(FlowContext context, object message)
         {
-            if (context.Reply == null)
+            var reply = context.FlowState.Metadata.Reply;
-                throw new InvalidOperationException("No response is required");
+            if (reply == null)
+                throw new YieldPointException("No response is required");
 
-            if (message.GetType().FullName != context.Reply.ResponseTypeName)
+            if (message.GetType().FullName != reply.ResponseTypeName)
-                throw new InvalidOperationException($"Flow must end with a response message of type {context.Reply.ResponseTypeName}, {message.GetType().FullName} was returned instead");
+                throw new YieldPointException($"Flow must end with a response message of type {reply.ResponseTypeName}, {message.GetType().FullName} was returned instead");
 
-            var properties = new BasicProperties
+            var properties = new BasicProperties();
-            {
-                CorrelationId = context.Reply.CorrelationId
-            };
 
-            await publisher.PublishDirect(message, context.Reply.ReplyTo, properties);
+            // Only set the property if it's not null, otherwise a string reference exception can occur:
+            // http://rabbitmq.1065348.n5.nabble.com/SocketException-when-invoking-model-BasicPublish-td36330.html
+            if (reply.CorrelationId != null)
+                properties.CorrelationId = reply.CorrelationId;
+
+            // TODO disallow if replyto is not specified?
+            if (context.FlowState.Metadata.Reply.ReplyTo != null)
+                await publisher.PublishDirect(message, reply.ReplyTo, properties);
+            else
+                await publisher.Publish(message, properties);
         }
 
 
         private static Task EndFlow(FlowContext context)
         {
-            if (context.Reply != null)
+            if (context.FlowState.Metadata.Reply != null)
-                throw new InvalidOperationException($"Flow must end with a response message of type {context.Reply.ResponseTypeName}");
+                throw new YieldPointException($"Flow must end with a response message of type {context.FlowState.Metadata.Reply.ResponseTypeName}");
 
             return Task.CompletedTask;
         }
@@ -107,6 +115,10 @@ namespace Tapeti.Flow.Default
             if (requestAttribute?.Response != null && requestAttribute.Response != binding.MessageClass)
                 throw new ArgumentException($"responseHandler must accept message of type {binding.MessageClass}", nameof(responseHandler));
 
+            var continuationAttribute = binding.Method.GetCustomAttribute<ContinuationAttribute>();
+            if (continuationAttribute == null)
+                throw new ArgumentException($"responseHandler must be marked with the Continuation attribute", nameof(responseHandler));
+
             return new ResponseHandlerInfo
             {
                 MethodName = MethodSerializer.Serialize(responseHandler.Method),
@@ -115,16 +127,71 @@ namespace Tapeti.Flow.Default
         }
 
 
+        private static ReplyMetadata GetReply(IMessageContext context)
+        {
+            var requestAttribute = context.Message.GetType().GetCustomAttribute<RequestAttribute>();
+            if (requestAttribute?.Response == null)
+                return null;
+
+            return new ReplyMetadata
+            {
+                CorrelationId = context.Properties.CorrelationId,
+                ReplyTo = context.Properties.ReplyTo,
+                ResponseTypeName = requestAttribute.Response.FullName
+            };
+        }
+
+
         public async Task Execute(IMessageContext context, IYieldPoint yieldPoint)
         {
-            var flowContext = (FlowContext)context.Items[ContextItems.FlowContext];
-            if (flowContext == null)
-                return;
-
             var delegateYieldPoint = (DelegateYieldPoint)yieldPoint;
-            await delegateYieldPoint.Execute(flowContext);
+            var storeState = delegateYieldPoint.StoreState;
 
-            if (delegateYieldPoint.StoreState)
+            FlowContext flowContext;
+            object flowContextItem;
+
+            if (!context.Items.TryGetValue(ContextItems.FlowContext, out flowContextItem))
+            {
+                flowContext = new FlowContext
+                {
+                    MessageContext = context
+                };
+
+                if (storeState)
+                {
+                    // Initiate the flow
+                    var flowStore = context.DependencyResolver.Resolve<IFlowStore>();
+
+                    var flowID = Guid.NewGuid();
+                    flowContext.FlowStateLock = await flowStore.LockFlowState(flowID);
+
+                    if (flowContext.FlowStateLock == null)
+                        throw new InvalidOperationException("Unable to lock a new flow");
+
+                    flowContext.FlowState = await flowContext.FlowStateLock.GetFlowState();
+                    if (flowContext.FlowState == null)
+                        throw new InvalidOperationException("Unable to get state for new flow");
+
+                    flowContext.FlowState.Metadata.Reply = GetReply(context);
+                }
+            }
+            else
+                flowContext = (FlowContext) flowContextItem;
+
+
+            try
+            {
+                await delegateYieldPoint.Execute(flowContext);
+            }
+            catch (YieldPointException e)
+            {
+                var controllerName = flowContext.MessageContext.Controller.GetType().FullName;
+                var methodName = flowContext.MessageContext.Binding.Method.Name;
+
+                throw new YieldPointException($"{e.Message} in controller {controllerName}, method {methodName}", e);
+            }
+
+            if (storeState)
             {
                 flowContext.FlowState.Data = Newtonsoft.Json.JsonConvert.SerializeObject(context.Controller);
                 await flowContext.FlowStateLock.StoreFlowState(flowContext.FlowState);
@@ -202,61 +269,5 @@ namespace Tapeti.Flow.Default
             public string MethodName { get; set; }
             public string ReplyToQueue { get; set; }
         }
-
-
-
-        /*
-         * Handle response (correlationId known)
-            internal async Task HandleMessage(object message, string correlationID)
-            {
-                var continuationID = Guid.Parse(correlationID);
-                var flowStateID = await owner.flowStore.FindFlowStateID(continuationID);
-
-                if (!flowStateID.HasValue)
-                    return;
-
-                using (flowStateLock = await owner.flowStore.LockFlowState(flowStateID.Value))
-                {
-                    flowState = await flowStateLock.GetFlowState();
-
-                    continuation = flowState.Continuations[continuationID];
-                    if (continuation != null)
-                        await HandleContinuation(message);
-                }
-            }
-
-            private async Task HandleContinuation(object message)
-            {
-                var flowMetaData = Newtonsoft.Json.JsonConvert.DeserializeObject<FlowMetaData>(flowState.MetaData);
-                var continuationMetaData =
-                    Newtonsoft.Json.JsonConvert.DeserializeObject<ContinuationMetaData>(continuation.MetaData);
-
-                reply = flowMetaData.Reply;
-                controllerType = owner.GetControllerType(flowMetaData.ControllerTypeName);
-                method = controllerType.GetMethod(continuationMetaData.MethodName);
-
-                controller = owner.container.GetInstance(controllerType);
-
-                Newtonsoft.Json.JsonConvert.PopulateObject(flowState.Data, controller);
-
-                var yieldPoint = (AbstractYieldPoint) await owner.CallFlowController(controller, method, message);
-
-                await yieldPoint.Execute(this);
-
-                if (yieldPoint.Store)
-                {
-                    flowState.Data = Newtonsoft.Json.JsonConvert.SerializeObject(controller);
-                    flowState.Continuations.Remove(continuation);
-
-                    await flowStateLock.StoreFlowState(flowState);
-                }
-                else
-                {
-                    await flowStateLock.DeleteFlowState();
-                }
-            }
-
-        }
-        */
     }
 }

Tapeti.Flow/Default/FlowState.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Tapeti.Flow.Default
+{
+    public class FlowState
+    {
+        private FlowMetadata metadata;
+        private Dictionary<Guid, ContinuationMetadata> continuations;
+
+
+        public FlowMetadata Metadata
+        {
+            get { return metadata ?? (metadata = new FlowMetadata()); }
+            set { metadata = value; }
+        }
+
+        public string Data { get; set; }
+
+        public Dictionary<Guid, ContinuationMetadata> Continuations
+        {
+            get { return continuations ?? (continuations = new Dictionary<Guid, ContinuationMetadata>()); }
+            set { continuations = value; }
+        }
+
+
+        public void Assign(FlowState value)
+        {
+            Metadata = value.Metadata.Clone();
+            Data = value.Data;
+            Continuations = value.Continuations.ToDictionary(kv => kv.Key, kv => kv.Value.Clone());
+        }
+
+
+        public FlowState Clone()
+        {
+            var result = new FlowState();
+            result.Assign(this);
+
+            return result;
+        }
+    }
+
+
+    public class FlowMetadata
+    {
+        public ReplyMetadata Reply { get; set; }
+
+
+        public FlowMetadata Clone()
+        {
+            return new FlowMetadata
+            {
+                Reply = Reply?.Clone()
+            };
+        }
+    }
+
+
+    public class ReplyMetadata
+    {
+        public string ReplyTo { get; set; }
+        public string CorrelationId { get; set; }
+        public string ResponseTypeName { get; set; }
+
+
+        public ReplyMetadata Clone()
+        {
+            return new ReplyMetadata
+            {
+                ReplyTo = ReplyTo,
+                CorrelationId = CorrelationId,
+                ResponseTypeName = ResponseTypeName
+            };
+        }
+    }
+
+
+    public class ContinuationMetadata
+    {
+        public string MethodName { get; set; }
+        public string ConvergeMethodName { get; set; }
+
+
+        public ContinuationMetadata Clone()
+        {
+            return new ContinuationMetadata
+            {
+                MethodName = MethodName,
+                ConvergeMethodName = ConvergeMethodName
+            };
+        }
+    }
+}

Tapeti.Flow/Default/FlowStore.cs

@@ -1,17 +1,19 @@
-using System;
+using Newtonsoft.Json;
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 
-namespace Tapeti.Flow
+namespace Tapeti.Flow.Default
 {
     public class FlowStore : IFlowStore
     {
+        private static readonly ConcurrentDictionary<Guid, FlowState> FlowStates = new ConcurrentDictionary<Guid, FlowState>();
+        private static readonly ConcurrentDictionary<Guid, Guid> ContinuationLookup = new ConcurrentDictionary<Guid, Guid>();
+
         private readonly IFlowRepository repository;
-        private readonly ConcurrentDictionary<Guid, FlowState> flowStates = new ConcurrentDictionary<Guid, FlowState>();
-        private readonly ConcurrentDictionary<Guid, Guid> continuationLookup = new ConcurrentDictionary<Guid, Guid>();
 
 
         public FlowStore(IFlowRepository repository) 
@@ -22,41 +24,37 @@ namespace Tapeti.Flow
 
         public async Task Load()
         {
-            flowStates.Clear();
+            FlowStates.Clear();
-            continuationLookup.Clear();
+            ContinuationLookup.Clear();
 
-            foreach (var state in await repository.GetAllStates())
+            foreach (var flowStateRecord in await repository.GetStates())
             {
-                flowStates.GetOrAdd(state.FlowID, new FlowState
+                var flowState = ToFlowState(flowStateRecord);
-                {
+                FlowStates.GetOrAdd(flowStateRecord.FlowID, flowState);
-                    Metadata = state.Metadata,
-                    Data = state.Data,
-                    Continuations = state.Continuations
-                });
 
-                foreach (var continuation in state.Continuations)
+                foreach (var continuation in flowStateRecord.ContinuationMetadata)
-                    continuationLookup.GetOrAdd(continuation.Key, state.FlowID);
+                    ContinuationLookup.GetOrAdd(continuation.Key, flowStateRecord.FlowID);
             }
         }
 
 
-        public Task<Guid?> FindFlowStateID(Guid continuationID)
+        public Task<Guid?> FindFlowID(Guid continuationID)
         {
             Guid result;
-            return Task.FromResult(continuationLookup.TryGetValue(continuationID, out result) ? result : (Guid?)null);
+            return Task.FromResult(ContinuationLookup.TryGetValue(continuationID, out result) ? result : (Guid?)null);
         }
 
 
-        public async Task<IFlowStateLock> LockFlowState(Guid flowStateID)
+        public async Task<IFlowStateLock> LockFlowState(Guid flowID)
         {
             var isNew = false;
-            var flowState = flowStates.GetOrAdd(flowStateID, id =>
+            var flowState = FlowStates.GetOrAdd(flowID, id =>
             {
                 isNew = true;
                 return new FlowState();
             });
 
-            var result = new FlowStateLock(this, flowState, flowStateID, isNew);
+            var result = new FlowStateLock(this, flowState, flowID, isNew);
             await result.Lock();
 
             return result;
@@ -103,7 +101,7 @@ namespace Tapeti.Flow
                 }
             }
 
-            public Guid FlowStateID => flowID;
+            public Guid FlowID => flowID;
 
             public Task<FlowState> GetFlowState()
             {
@@ -112,12 +110,7 @@ namespace Tapeti.Flow
                     if (isDisposed)
                         throw new ObjectDisposedException("FlowStateLock");
 
-                    return Task.FromResult(new FlowState
+                    return Task.FromResult(flowState.Clone());
-                    {
-                        Data = flowState.Data,
-                        Metadata = flowState.Metadata,
-                        Continuations = flowState.Continuations.ToDictionary(kv => kv.Key, kv => kv.Value)
-                    });
                 }
             }
 
@@ -128,37 +121,29 @@ namespace Tapeti.Flow
                     if (isDisposed)
                         throw new ObjectDisposedException("FlowStateLock");
 
-                    foreach (
+                    foreach (var removedContinuation in flowState.Continuations.Keys.Where(k => !newFlowState.Continuations.ContainsKey(k)))
-                        var removedContinuation in
-                            flowState.Continuations.Keys.Where(
-                                k => !newFlowState.Continuations.ContainsKey(k)))
                     {
                         Guid removedValue;
-                        owner.continuationLookup.TryRemove(removedContinuation, out removedValue);
+                        ContinuationLookup.TryRemove(removedContinuation, out removedValue);
                     }
 
-                    foreach (
+                    foreach (var addedContinuation in newFlowState.Continuations.Where(c => !flowState.Continuations.ContainsKey(c.Key)))
-                        var addedContinuation in
-                            newFlowState.Continuations.Where(
-                                c => !flowState.Continuations.ContainsKey(c.Key)))
                     {
-                        owner.continuationLookup.TryAdd(addedContinuation.Key, flowID);
+                        ContinuationLookup.TryAdd(addedContinuation.Key, flowID);
                     }
 
-                    flowState.Metadata = newFlowState.Metadata;
+                    flowState.Assign(newFlowState);
-                    flowState.Data = newFlowState.Data;
-                    flowState.Continuations = newFlowState.Continuations.ToDictionary(kv => kv.Key, kv => kv.Value);
                 }
+
                 if (isNew)
                 {
                     isNew = false;
                     var now = DateTime.UtcNow;
-                    await
+                    await owner.repository.CreateState(ToFlowStateRecord(flowID, flowState), now);
-                        owner.repository.CreateState(flowID, now, flowState.Metadata, flowState.Data, flowState.Continuations);
                 }
                 else
                 {
-                    await owner.repository.UpdateState(flowID, flowState.Metadata, flowState.Data, flowState.Continuations);
+                    await owner.repository.UpdateState(ToFlowStateRecord(flowID, flowState));
                 }
             }
 
@@ -172,15 +157,42 @@ namespace Tapeti.Flow
                     foreach (var removedContinuation in flowState.Continuations.Keys)
                     {
                         Guid removedValue;
-                        owner.continuationLookup.TryRemove(removedContinuation, out removedValue);
+                        ContinuationLookup.TryRemove(removedContinuation, out removedValue);
                     }
+
                     FlowState removedFlow;
-                    owner.flowStates.TryRemove(flowID, out removedFlow);
+                    FlowStates.TryRemove(flowID, out removedFlow);
                 }
+
                 if (!isNew)
                     await owner.repository.DeleteState(flowID);
             }
+        }
 
+
+        private static FlowStateRecord ToFlowStateRecord(Guid flowID, FlowState flowState)
+        {
+            return new FlowStateRecord
+            {
+                FlowID = flowID,
+                Metadata = JsonConvert.SerializeObject(flowState.Metadata),
+                Data = flowState.Data,
+                ContinuationMetadata = flowState.Continuations.ToDictionary(
+                    kv => kv.Key, 
+                    kv => JsonConvert.SerializeObject(kv.Value))
+            };
+        }
+
+        private static FlowState ToFlowState(FlowStateRecord flowStateRecord)
+        {
+            return new FlowState
+            {
+                Metadata = JsonConvert.DeserializeObject<FlowMetadata>(flowStateRecord.Metadata),
+                Data = flowStateRecord.Data,
+                Continuations = flowStateRecord.ContinuationMetadata.ToDictionary(
+                    kv => kv.Key, 
+                    kv => JsonConvert.DeserializeObject<ContinuationMetadata>(kv.Value))
+            };
         }
     }
 }

Tapeti.Flow/Default/NonPersistentFlowRepository.cs

@@ -7,17 +7,17 @@ namespace Tapeti.Flow.Default
 {
     public class NonPersistentFlowRepository : IFlowRepository
     {
-        public Task<IQueryable<FlowStateRecord>> GetAllStates()
+        public Task<IQueryable<FlowStateRecord>> GetStates()
         {
             return Task.FromResult(new List<FlowStateRecord>().AsQueryable());
         }
 
-        public Task CreateState(Guid flowID, DateTime timestamp, string metadata, string data, IDictionary<Guid, string> continuations)
+        public Task CreateState(FlowStateRecord stateRecord, DateTime timestamp)
         {
             return Task.CompletedTask;
         }
 
-        public Task UpdateState(Guid flowID, string metadata, string data, IDictionary<Guid, string> continuations)
+        public Task UpdateState(FlowStateRecord stateRecord)
         {
             return Task.CompletedTask;
         }

Tapeti.Flow/FlowMiddleware.cs

@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using Tapeti.Config;
 using Tapeti.Flow.Annotations;
 using Tapeti.Flow.Default;
+using Tapeti.Helpers;
 
 namespace Tapeti.Flow
 {
@@ -13,13 +14,14 @@ namespace Tapeti.Flow
         public IEnumerable<object> GetContents(IDependencyResolver dependencyResolver)
         {
             var container = dependencyResolver as IDependencyContainer;
+
+            // ReSharper disable once InvertIf
             if (container != null)
             {
                 container.RegisterDefault<IFlowProvider, FlowProvider>();
                 container.RegisterDefault<IFlowHandler, FlowProvider>();
-                // TODO singleton
-                container.RegisterDefault<IFlowStore, FlowStore>();
                 container.RegisterDefault<IFlowRepository, NonPersistentFlowRepository>();
+                container.RegisterDefault<IFlowStore, FlowStore>();
             }
 
             return new[] { new FlowBindingMiddleware() };
@@ -30,40 +32,41 @@ namespace Tapeti.Flow
         {
             public void Handle(IBindingContext context, Action next)
             {
-                HandleContinuationFilter(context);
+                RegisterContinuationFilter(context);
-                HandleYieldPointResult(context);
+                RegisterYieldPointResult(context);
 
                 next();
             }
 
 
-            private static void HandleContinuationFilter(IBindingContext context)
+            private static void RegisterContinuationFilter(IBindingContext context)
             {
                 var continuationAttribute = context.Method.GetCustomAttribute<ContinuationAttribute>();
-                if (continuationAttribute != null)
+                if (continuationAttribute == null)
-                {
+                    return;
-                    context.Use(new FlowBindingFilter());
+
-                    context.Use(new FlowMessageMiddleware());
+                context.Use(new FlowBindingFilter());
-                }
+                context.Use(new FlowMessageMiddleware());
             }
 
 
-            private static void HandleYieldPointResult(IBindingContext context)
+            private static void RegisterYieldPointResult(IBindingContext context)
             {
-                if (context.Result.Info.ParameterType == typeof(IYieldPoint))
+                bool isTask;
-                    context.Result.SetHandler((messageContext, value) => HandleYieldPoint(messageContext, (IYieldPoint)value));
+                if (!context.Result.Info.ParameterType.IsTypeOrTaskOf(typeof(IYieldPoint), out isTask))
+                    return;
 
-                else if (context.Result.Info.ParameterType == typeof(Task<>))
+                if (isTask)
                 {
-                    var genericArguments = context.Result.Info.ParameterType.GetGenericArguments();
+                    context.Result.SetHandler(async (messageContext, value) =>
-                    if (genericArguments.Length == 1 && genericArguments[0] == typeof(IYieldPoint))
+                    {
-                        context.Result.SetHandler(async (messageContext, value) =>
+                        var yieldPoint = await (Task<IYieldPoint>)value;
-                        {
+                        if (yieldPoint != null)
-                            var yieldPoint = await (Task<IYieldPoint>)value;
+                            await HandleYieldPoint(messageContext, yieldPoint);
-                            if (yieldPoint != null)
+                    });
-                                await HandleYieldPoint(messageContext, yieldPoint);
-                        });
                 }
+                else
+                    context.Result.SetHandler((messageContext, value) => HandleYieldPoint(messageContext, (IYieldPoint)value));
             }
 
 

Tapeti.Flow/IFlowRepository.cs

@@ -7,9 +7,9 @@ namespace Tapeti.Flow
 {
     public interface IFlowRepository
     {
-        Task<IQueryable<FlowStateRecord>> GetAllStates();
+        Task<IQueryable<FlowStateRecord>> GetStates();
-        Task CreateState(Guid flowID, DateTime timestamp, string metadata, string data, IDictionary<Guid, string> continuations);
+        Task CreateState(FlowStateRecord stateRecord, DateTime timestamp);
-        Task UpdateState(Guid flowID, string metadata, string data, IDictionary<Guid, string> continuations);
+        Task UpdateState(FlowStateRecord stateRecord);
         Task DeleteState(Guid flowID);
     }
 
@@ -19,6 +19,6 @@ namespace Tapeti.Flow
         public Guid FlowID;
         public string Metadata;
         public string Data;
-        public Dictionary<Guid, string> Continuations;
+        public Dictionary<Guid, string> ContinuationMetadata;
     }
 }

Tapeti.Flow/IFlowStore.cs

@@ -1,28 +1,23 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Tapeti.Flow.Default;
 
 namespace Tapeti.Flow
 {
     public interface IFlowStore
     {
         Task Load();
-        Task<Guid?> FindFlowStateID(Guid continuationID);
+        Task<Guid?> FindFlowID(Guid continuationID);
-        Task<IFlowStateLock> LockFlowState(Guid flowStateID);
+        Task<IFlowStateLock> LockFlowState(Guid flowID);
     }
 
     public interface IFlowStateLock : IDisposable
     {
-        Guid FlowStateID { get; }
+        Guid FlowID { get; }
+
         Task<FlowState> GetFlowState();
         Task StoreFlowState(FlowState flowState);
         Task DeleteFlowState();
     }
-
-    public class FlowState
-    {
-        public string Metadata { get; set; }
-        public string Data { get; set; }
-        public Dictionary<Guid, string> Continuations { get; set; }
-    }
 }

Tapeti.Flow/Properties/AssemblyInfo.cs

@@ -1,5 +1,4 @@
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 // General Information about an assembly is controlled through the following 

Tapeti.Flow/Tapeti.Flow.csproj

@@ -55,8 +55,10 @@
     <Compile Include="Default\FlowBindingFilter.cs" />
     <Compile Include="Default\FlowContext.cs" />
     <Compile Include="Default\FlowMessageMiddleware.cs" />
+    <Compile Include="Default\FlowState.cs" />
     <Compile Include="Default\NonPersistentFlowRepository.cs" />
     <Compile Include="Default\DelegateYieldPoint.cs" />
+    <Compile Include="ConfigExtensions.cs" />
     <Compile Include="FlowHelpers\MethodSerializer.cs" />
     <Compile Include="FlowMiddleware.cs" />
     <Compile Include="Default\FlowStore.cs" />
@@ -65,6 +67,7 @@
     <Compile Include="IFlowStore.cs" />
     <Compile Include="IFlowProvider.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="YieldPointException.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Tapeti.csproj">

Tapeti.Flow/YieldPointException.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Tapeti.Flow
+{
+    public class YieldPointException : Exception
+    {
+        public YieldPointException(string message) : base(message) { }
+        public YieldPointException(string message, Exception innerException) : base(message, innerException) { }
+    }
+}

Tapeti.SimpleInjector/SimpleInjectorDependencyResolver.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Linq;
 using SimpleInjector;
-using Tapeti.Config;
 
 namespace Tapeti.SimpleInjector
 {
@@ -27,29 +26,44 @@ namespace Tapeti.SimpleInjector
 
         public void RegisterDefault<TService, TImplementation>() where TService : class where TImplementation : class, TService
         {
-            // ReSharper disable once SimplifyLinqExpression - not a fan of negative predicates
+            if (CanRegisterDefault<TService>())
-            if (!container.GetCurrentRegistrations().Any(ip => ip.ServiceType == typeof(TService)))
                 container.Register<TService, TImplementation>();
         }
 
-
+        public void RegisterDefault<TService>(Func<TService> factory) where TService : class
-        public void RegisterConfig(IConfig config)
         {
-            container.RegisterSingleton(config);
+            if (CanRegisterDefault<TService>())
+                container.Register(factory);
         }
 
-
+        public void RegisterDefaultSingleton<TService, TImplementation>() where TService : class where TImplementation : class, TService
-        public void RegisterPublisher(Func<IPublisher> publisher)
         {
-            // ReSharper disable once SimplifyLinqExpression - still not a fan of negative predicates
+            if (CanRegisterDefault<TService>())
-            if (!container.GetCurrentRegistrations().Any(ip => ip.ServiceType == typeof(IPublisher)))
+                container.RegisterSingleton<TService, TImplementation>();
-                container.Register(publisher);
         }
 
+        public void RegisterDefaultSingleton<TService>(TService instance) where TService : class
+        {
+            if (CanRegisterDefault<TService>())
+                container.RegisterSingleton(instance);
+        }
+
+        public void RegisterDefaultSingleton<TService>(Func<TService> factory) where TService : class
+        {
+            if (CanRegisterDefault<TService>())
+                container.RegisterSingleton(factory);
+        }
 
         public void RegisterController(Type type)
         {
             container.Register(type);
         }
+
+
+        private bool CanRegisterDefault<TService>() where TService : class
+        {
+            // ReSharper disable once SimplifyLinqExpression - not a fan of negative predicates
+            return !container.GetCurrentRegistrations().Any(ip => ip.ServiceType == typeof(TService));
+        }
     }
 }

Tapeti.csproj

@@ -61,10 +61,12 @@
     <Compile Include="Default\ConsoleLogger.cs" />
     <Compile Include="Default\DevNullLogger.cs" />
     <Compile Include="Default\JsonMessageSerializer.cs" />
+    <Compile Include="Default\PublishResultBinding.cs" />
     <Compile Include="Default\NamespaceMatchExchangeStrategy.cs" />
     <Compile Include="Default\TypeNameRoutingKeyStrategy.cs" />
     <Compile Include="Helpers\ConsoleHelper.cs" />
     <Compile Include="Helpers\MiddlewareHelper.cs" />
+    <Compile Include="Helpers\TaskTypeHelper.cs" />
     <Compile Include="IConnection.cs" />
     <Compile Include="IExchangeStrategy.cs" />
     <Compile Include="ILogger.cs" />

Tapeti.sln.DotSettings.user

@@ -1,5 +0,0 @@
-<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
-	<s:Boolean x:Key="/Default/Housekeeping/Bookmarks/NumberedBookmarks/=Bookmark9/@KeyIndexDefined">True</s:Boolean>
-	<s:String x:Key="/Default/Housekeeping/Bookmarks/NumberedBookmarks/=Bookmark9/Coords/@EntryValue">(Doc Ln 29 Col 51)</s:String>
-	<s:String x:Key="/Default/Housekeeping/Bookmarks/NumberedBookmarks/=Bookmark9/FileId/@EntryValue">F84AD920-D5A1-455D-AED5-2542B3A47B85/d:Default/f:FlowProvider.cs</s:String>
-	<s:String x:Key="/Default/Housekeeping/Bookmarks/NumberedBookmarks/=Bookmark9/Owner/@EntryValue">NumberedBookmarkManager</s:String></wpf:ResourceDictionary>

TapetiConfig.cs

@@ -16,7 +16,7 @@ namespace Tapeti
         public TopologyConfigurationException(string message) : base(message) { }
     }
 
-    public delegate Task<object> MessageHandlerFunc(IMessageContext context, object message);
+    public delegate Task MessageHandlerFunc(IMessageContext context, object message);
 
 
     public class TapetiConfig
@@ -27,17 +27,18 @@ namespace Tapeti
         private readonly List<IBindingMiddleware> bindingMiddleware = new List<IBindingMiddleware>();
         private readonly List<IMessageMiddleware> messageMiddleware = new List<IMessageMiddleware>();
 
-        private readonly string exchange;
+        private readonly string subscribeExchange;
         private readonly IDependencyResolver dependencyResolver;
 
 
-        public TapetiConfig(string exchange, IDependencyResolver dependencyResolver)
+        public TapetiConfig(string subscribeExchange, IDependencyResolver dependencyResolver)
         {
-            this.exchange = exchange;
+            this.subscribeExchange = subscribeExchange;
             this.dependencyResolver = dependencyResolver;
 
             Use(new DependencyResolverBinding());
             Use(new MessageBinding());
+            Use(new PublishResultBinding());
         }
 
 
@@ -62,8 +63,8 @@ namespace Tapeti
 
             queues.AddRange(dynamicBindings.Select(bl => new Queue(new QueueInfo { Dynamic = true }, bl)));
 
-            var config = new Config(exchange, dependencyResolver, messageMiddleware, queues);
+            var config = new Config(subscribeExchange, dependencyResolver, messageMiddleware, queues);
-            (dependencyResolver as IDependencyContainer)?.RegisterConfig(config);
+            (dependencyResolver as IDependencyContainer)?.RegisterDefaultSingleton<IConfig>(config);
 
             return config;
         }
@@ -139,7 +140,8 @@ namespace Tapeti
                     QueueInfo = methodQueueInfo,
                     MessageClass = context.MessageClass,
                     MessageHandler = messageHandler,
-                    MessageMiddleware = context.MessageMiddleware
+                    MessageMiddleware = context.MessageMiddleware,
+                    BindingFilters = context.BindingFilters
                 };
 
                 if (methodQueueInfo.Dynamic.GetValueOrDefault())
@@ -177,61 +179,59 @@ namespace Tapeti
 
             var invalidBindings = context.Parameters.Where(p => !p.HasBinding).ToList();
 
-            // ReSharper disable once InvertIf - doesn't make the flow clearer imo
+            // ReSharper disable once InvertIf
             if (invalidBindings.Count > 0)
             {
                 var parameterNames = string.Join(", ", invalidBindings.Select(p => p.Info.Name));
                 throw new TopologyConfigurationException($"Method {method.Name} in controller {method.DeclaringType?.Name} has unknown parameters: {parameterNames}");
             }
 
-            return WrapMethod(method, context.Parameters.Select(p => ((IBindingParameterAccess)p).GetBinding()));
+            var resultHandler = ((IBindingResultAccess) context.Result).GetHandler();
+
+            return WrapMethod(method, context.Parameters.Select(p => ((IBindingParameterAccess)p).GetBinding()), resultHandler);
         }
 
 
-        protected MessageHandlerFunc WrapMethod(MethodInfo method, IEnumerable<ValueFactory> parameters)
+        protected MessageHandlerFunc WrapMethod(MethodInfo method, IEnumerable<ValueFactory> parameters, ResultHandler resultHandler)
         {
+            if (resultHandler != null)
+                return WrapResultHandlerMethod(method, parameters, resultHandler);
+
             if (method.ReturnType == typeof(void))
                 return WrapNullMethod(method, parameters);
 
             if (method.ReturnType == typeof(Task))
                 return WrapTaskMethod(method, parameters);
 
-            if (method.ReturnType == typeof(Task<>))
+            if (method.ReturnType.IsGenericType && method.ReturnType.GetGenericTypeDefinition() == typeof(Task<>))
-            {
-                var genericArguments = method.GetGenericArguments();
-                if (genericArguments.Length != 1)
-                    throw new ArgumentException($"Method {method.Name} in controller {method.DeclaringType?.Name} must have exactly one generic argument to Task<>");
-
-                if (!genericArguments[0].IsClass)
-                    throw new ArgumentException($"Method {method.Name} in controller {method.DeclaringType?.Name} must have an object generic argument to Task<>");
-
                 return WrapGenericTaskMethod(method, parameters);
-            }
 
-            if (method.ReturnType.IsClass)
+            return WrapObjectMethod(method, parameters);
-                return WrapObjectMethod(method, parameters);
-
-            throw new ArgumentException($"Method {method.Name} in controller {method.DeclaringType?.Name} has an invalid return type");
         }
 
 
+        protected MessageHandlerFunc WrapResultHandlerMethod(MethodInfo method, IEnumerable<ValueFactory> parameters, ResultHandler resultHandler)
+        {
+            return (context, message) =>
+            {
+                var result = method.Invoke(context.Controller, parameters.Select(p => p(context)).ToArray());
+                return resultHandler(context, result);
+            };
+        }
+
         protected MessageHandlerFunc WrapNullMethod(MethodInfo method, IEnumerable<ValueFactory> parameters)
         {
             return (context, message) =>
             {
                 method.Invoke(context.Controller, parameters.Select(p => p(context)).ToArray());
-                return Task.FromResult<object>(null);
+                return Task.CompletedTask;
             };
         }
 
 
         protected MessageHandlerFunc WrapTaskMethod(MethodInfo method, IEnumerable<ValueFactory> parameters)
         {
-            return async (context, message) =>
+            return (context, message) => (Task)method.Invoke(context.Controller, parameters.Select(p => p(context)).ToArray());
-            {
-                await (Task)method.Invoke(context.Controller, parameters.Select(p => p(context)).ToArray());
-                return Task.FromResult<object>(null);
-            };
         }
 
 
@@ -310,7 +310,7 @@ namespace Tapeti
 
         protected class Config : IConfig
         {
-            public string Exchange { get; }
+            public string SubscribeExchange { get; }
             public IDependencyResolver DependencyResolver { get; }
             public IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; }
             public IEnumerable<IQueue> Queues { get; }
@@ -318,9 +318,9 @@ namespace Tapeti
             private readonly Dictionary<MethodInfo, IBinding> bindingMethodLookup;
 
 
-            public Config(string exchange, IDependencyResolver dependencyResolver, IReadOnlyList<IMessageMiddleware> messageMiddleware, IEnumerable<IQueue> queues)
+            public Config(string subscribeExchange, IDependencyResolver dependencyResolver, IReadOnlyList<IMessageMiddleware> messageMiddleware, IEnumerable<IQueue> queues)
             {
-                Exchange = exchange;
+                SubscribeExchange = subscribeExchange;
                 DependencyResolver = dependencyResolver;
                 MessageMiddleware = messageMiddleware;
                 Queues = queues.ToList();
@@ -361,6 +361,7 @@ namespace Tapeti
             public string QueueName { get; set; }
 
             public IReadOnlyList<IMessageMiddleware> MessageMiddleware { get; set;  }
+            public IReadOnlyList<IBindingFilter> BindingFilters { get; set; }
 
             private QueueInfo queueInfo;
             public QueueInfo QueueInfo
@@ -382,13 +383,25 @@ namespace Tapeti
             }
 
 
-            public bool Accept(object message)
+            public async Task<bool> Accept(IMessageContext context, object message)
             {
-                return message.GetType() == MessageClass;
+                if (message.GetType() != MessageClass)
+                    return false;
+
+                if (BindingFilters == null)
+                    return true;
+
+                foreach (var filter in BindingFilters)
+                {
+                    if (!await filter.Accept(context, this))
+                        return false;
+                }
+
+                return true;
             }
 
 
-            public Task<object> Invoke(IMessageContext context, object message)
+            public Task Invoke(IMessageContext context, object message)
             {
                 return MessageHandler(context, message);
             }

TapetiConnection.cs

@@ -16,12 +16,12 @@ namespace Tapeti
         public TapetiConnection(IConfig config)
         {
             this.config = config;
-            (config.DependencyResolver as IDependencyContainer)?.RegisterPublisher(GetPublisher);
+            (config.DependencyResolver as IDependencyContainer)?.RegisterDefault(GetPublisher);
 
             worker = new Lazy<TapetiWorker>(() => new TapetiWorker(config.DependencyResolver, config.MessageMiddleware)
             {
                 ConnectionParams = Params ?? new TapetiConnectionParams(),
-                Exchange = config.Exchange
+                SubscribeExchange = config.SubscribeExchange
             });
         }
 

TapetiConnectionParams.cs

@@ -10,6 +10,13 @@ namespace Tapeti
         public string Username { get; set; } = "guest";
         public string Password { get; set; } = "guest";
 
+        /// <summary>
+        /// The amount of message to prefetch. See http://www.rabbitmq.com/consumer-prefetch.html for more information.
+        /// 
+        /// If set to 0, no limit will be applied.
+        /// </summary>
+        public ushort PrefetchCount { get; set; } = 50;
+
 
         public TapetiConnectionParams()
         {            

Test/MarcoController.cs

@@ -30,30 +30,30 @@ namespace Test
          * The Visualizer could've been injected through the constructor, which is
          * the recommended way. Just testing the injection middleware here.
          */
-        public async Task Marco(MarcoMessage message, Visualizer myVisualizer)
+        public async Task<IYieldPoint> Marco(MarcoMessage message, Visualizer myVisualizer)
         {
+            Console.WriteLine(">> Marco (yielding with request)");
+
             await myVisualizer.VisualizeMarco();
-            await publisher.Publish(new PoloMessage());
-        }
 
-
+            return flowProvider.YieldWithRequestSync<PoloConfirmationRequestMessage, PoloConfirmationResponseMessage>(
-        public IYieldPoint Polo(PoloMessage message)
-        {
-            StateTestGuid = Guid.NewGuid();
-
-            return flowProvider.YieldWithRequest<PoloConfirmationRequestMessage, PoloConfirmationResponseMessage>(
                 new PoloConfirmationRequestMessage()
                 {
                     StoredInState = StateTestGuid
-                }, 
+                },
                 HandlePoloConfirmationResponse);
         }
 
 
-        public async Task<IYieldPoint> HandlePoloConfirmationResponse(PoloConfirmationResponseMessage message)
+        [Continuation]
+        public IYieldPoint HandlePoloConfirmationResponse(PoloConfirmationResponseMessage message)
         {
-            await visualizer.VisualizePolo(message.ShouldMatchState.Equals(StateTestGuid));
+            Console.WriteLine(">> HandlePoloConfirmationResponse (ending flow)");
-            return flowProvider.End();
+
+            Console.WriteLine(message.ShouldMatchState.Equals(StateTestGuid) ? "Confirmed!" : "Oops! Mismatch!");
+
+            // This should error, as MarcoMessage expects a PoloMessage as a response
+            return flowProvider.EndWithResponse(new PoloMessage());
         }
 
 
@@ -63,16 +63,28 @@ namespace Test
          * use the replyTo header of the request if provided.
          */
 
+        // TODO validation middleware to ensure a request message returns the specified response (already done for IYieldPoint methods)
         public PoloConfirmationResponseMessage PoloConfirmation(PoloConfirmationRequestMessage message)
         {
+            Console.WriteLine(">> PoloConfirmation (returning confirmation)");
+
             return new PoloConfirmationResponseMessage
             {
                 ShouldMatchState = message.StoredInState
             };
         }
+
+
+
+        public void Polo(PoloMessage message)
+        {
+            Console.WriteLine(">> Polo");
+            StateTestGuid = Guid.NewGuid();
+        }
     }
 
 
+    [Request(Response = typeof(PoloMessage))]
     public class MarcoMessage
     {
     }

Test/MarcoEmitter.cs

@@ -17,20 +17,33 @@ namespace Test
 
         public async Task Run()
         {
+            await publisher.Publish(new MarcoMessage());
+
+            /*
             var concurrent = new SemaphoreSlim(20);
 
-            //for (var x = 0; x < 5000; x++)
             while (true)
             {
-                await concurrent.WaitAsync();
+                for (var x = 0; x < 200; x++)
-                try
                 {
-                    await publisher.Publish(new MarcoMessage());
+                    await concurrent.WaitAsync();
-                }
+                    try
-                finally
+                    {
-                {
+                        await publisher.Publish(new MarcoMessage());
-                    concurrent.Release();
+                    }
+                    finally
+                    {
+                        concurrent.Release();
+                    }
                 }
+
+                await Task.Delay(1000);
+            }
+            */
+
+            while (true)
+            {
+                await Task.Delay(1000);
             }
         }
     }

Test/Program.cs

@@ -13,15 +13,21 @@ namespace Test
             var container = new Container();
             container.Register<MarcoEmitter>();
             container.Register<Visualizer>();
-            //container.RegisterSingleton<ISagaStore, SagaMemoryStore>();
 
             var config = new TapetiConfig("test", new SimpleInjectorDependencyResolver(container))
-                .Use(new FlowMiddleware())
+                .WithFlow()
                 .RegisterAllControllers()
                 .Build();
 
-            using (var connection = new TapetiConnection(config))
+            using (var connection = new TapetiConnection(config)
-            {   
+            {
+                Params = new TapetiConnectionParams
+                {
+                    HostName = "localhost",
+                    PrefetchCount = 200
+                }
+            })
+            {
                 Console.WriteLine("Subscribing...");
                 connection.Subscribe().Wait();
                 Console.WriteLine("Done!");

Test/Properties/AssemblyInfo.cs

@@ -7,9 +7,9 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTitle("Test")]
 [assembly: AssemblyDescription("")]
 [assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("Hewlett-Packard Company")]
+[assembly: AssemblyCompany("")]
 [assembly: AssemblyProduct("Test")]
-[assembly: AssemblyCopyright("Copyright © Hewlett-Packard Company 2016")]
+[assembly: AssemblyCopyright("")]
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 

Test/Visualizer.cs

@@ -11,9 +11,9 @@ namespace Test
             return Task.CompletedTask;
         }
 
-        public Task VisualizePolo(bool matches)
+        public Task VisualizePolo()
         {
-            Console.WriteLine(matches ? "Polo!" : "Oops! Mismatch!");
+            Console.WriteLine("Polo!");
             return Task.CompletedTask;
         }
     }