Fixed #11: Do not persist flow for dynamic queues

Tapeti.Flow/Default/FlowBindingMiddleware.cs

@@ -86,7 +86,7 @@ namespace Tapeti.Flow.Default
             var flowHandler = context.Config.DependencyResolver.Resolve<IFlowHandler>();
             return flowHandler.Execute(new FlowHandlerContext(context), new DelegateYieldPoint(async flowContext =>
             {
-                await flowContext.Store();
+                await flowContext.Store(context.Binding.QueueType == QueueType.Durable);
             }));
         }
 

Tapeti.Flow/Default/FlowContext.cs

@@ -16,7 +16,7 @@ namespace Tapeti.Flow.Default
         private bool deleteCalled;
 
 
-        public async Task Store()
+        public async Task Store(bool persistent)
         {
             storeCalled = true;
 
@@ -25,7 +25,7 @@ namespace Tapeti.Flow.Default
             if (FlowStateLock == null) throw new ArgumentNullException(nameof(FlowStateLock));
 
             FlowState.Data = Newtonsoft.Json.JsonConvert.SerializeObject(HandlerContext.Controller);
-            await FlowStateLock.StoreFlowState(FlowState);
+            await FlowStateLock.StoreFlowState(FlowState, persistent);
         }
 
         public async Task Delete()

Tapeti.Flow/Default/FlowProvider.cs

@@ -88,7 +88,7 @@ namespace Tapeti.Flow.Default
                 ReplyTo = responseHandlerInfo.ReplyToQueue
             };
 
-            await context.Store();
+            await context.Store(responseHandlerInfo.IsDurableQueue);
 
             await publisher.Publish(message, properties, true);
         }
@@ -153,7 +153,8 @@ namespace Tapeti.Flow.Default
             return new ResponseHandlerInfo
             {
                 MethodName = MethodSerializer.Serialize(responseHandler.Method),
-                ReplyToQueue = binding.QueueName
+                ReplyToQueue = binding.QueueName,
+                IsDurableQueue = binding.QueueType == QueueType.Durable
             };
         }
 
@@ -331,6 +332,7 @@ namespace Tapeti.Flow.Default
         {
             public string MethodName { get; set; }
             public string ReplyToQueue { get; set; }
+            public bool IsDurableQueue { get; set; }
         }
     }
 }

Tapeti.Flow/Default/FlowStore.cs

@@ -13,7 +13,19 @@ namespace Tapeti.Flow.Default
     /// </summary>
     public class FlowStore : IFlowStore
     {
-        private readonly ConcurrentDictionary<Guid, FlowState> flowStates = new ConcurrentDictionary<Guid, FlowState>();
+        private class CachedFlowState
+        {
+            public readonly FlowState FlowState;
+            public readonly bool IsPersistent;
+
+            public CachedFlowState(FlowState flowState, bool isPersistent)
+            {
+                FlowState = flowState;
+                IsPersistent = isPersistent;
+            }
+        }
+
+        private readonly ConcurrentDictionary<Guid, CachedFlowState> flowStates = new ConcurrentDictionary<Guid, CachedFlowState>();
         private readonly ConcurrentDictionary<Guid, Guid> continuationLookup = new ConcurrentDictionary<Guid, Guid>();
         private readonly LockCollection<Guid> locks = new LockCollection<Guid>(EqualityComparer<Guid>.Default);
 
@@ -43,7 +55,7 @@ namespace Tapeti.Flow.Default
 
             foreach (var flowStateRecord in await repository.GetStates<FlowState>())
             {
-                flowStates.TryAdd(flowStateRecord.Key, flowStateRecord.Value);
+                flowStates.TryAdd(flowStateRecord.Key, new CachedFlowState(flowStateRecord.Value, true));
 
                 foreach (var continuation in flowStateRecord.Value.Continuations)
                     continuationLookup.GetOrAdd(continuation.Key, flowStateRecord.Key);
@@ -80,7 +92,7 @@ namespace Tapeti.Flow.Default
         {
             private readonly FlowStore owner;
             private volatile IDisposable flowLock;
-            private FlowState flowState;
+            private CachedFlowState cachedFlowState;
 
             public Guid FlowID { get; }
 
@@ -91,7 +103,7 @@ namespace Tapeti.Flow.Default
                 FlowID = flowID;
                 this.flowLock = flowLock;
 
-                owner.flowStates.TryGetValue(flowID, out flowState);
+                owner.flowStates.TryGetValue(flowID, out cachedFlowState);
             }
 
             public void Dispose()
@@ -106,10 +118,10 @@ namespace Tapeti.Flow.Default
                 if (flowLock == null)
                     throw new ObjectDisposedException("FlowStateLock");
 
-                return Task.FromResult(flowState?.Clone());
+                return Task.FromResult(cachedFlowState.FlowState?.Clone());
             }
 
-            public async Task StoreFlowState(FlowState newFlowState)
+            public async Task StoreFlowState(FlowState newFlowState, bool persistent)
             {
                 if (flowLock == null)
                     throw new ObjectDisposedException("FlowStateLock");
@@ -118,30 +130,41 @@ namespace Tapeti.Flow.Default
                 newFlowState = newFlowState.Clone();
 
                 // Update the lookup dictionary for the ContinuationIDs
-                if (flowState != null)
+                if (cachedFlowState != null)
                 {
-                    foreach (var removedContinuation in flowState.Continuations.Keys.Where(k => !newFlowState.Continuations.ContainsKey(k)))
+                    foreach (var removedContinuation in cachedFlowState.FlowState.Continuations.Keys.Where(k => !newFlowState.Continuations.ContainsKey(k)))
                         owner.continuationLookup.TryRemove(removedContinuation, out _);
                 }
 
-                foreach (var addedContinuation in newFlowState.Continuations.Where(c => flowState == null || !flowState.Continuations.ContainsKey(c.Key)))
+                foreach (var addedContinuation in newFlowState.Continuations.Where(c => cachedFlowState == null || !cachedFlowState.FlowState.Continuations.ContainsKey(c.Key)))
                 {
                     owner.continuationLookup.TryAdd(addedContinuation.Key, FlowID);
                 }
 
-                var isNew = flowState == null;
+                var isNew = cachedFlowState == null;
-                flowState = newFlowState;
+                var wasPersistent = cachedFlowState?.IsPersistent ?? false;
-                owner.flowStates[FlowID] = newFlowState;
 
+                cachedFlowState = new CachedFlowState(newFlowState, persistent);
+                owner.flowStates[FlowID] = cachedFlowState;
+
+                if (persistent)
+                {
                     // Storing the flowstate in the underlying repository
                     if (isNew)
                     {
                         var now = DateTime.UtcNow;
-                    await owner.repository.CreateState(FlowID, flowState, now);
+                        await owner.repository.CreateState(FlowID, cachedFlowState.FlowState, now);
                     }
                     else
                     {
-                    await owner.repository.UpdateState(FlowID, flowState);
+                        await owner.repository.UpdateState(FlowID, cachedFlowState.FlowState);
+                    }
+                }
+                else if (wasPersistent)
+                {
+                    // We transitioned from a durable queue to a dynamic queue,
+                    // remove the persistent state but keep the in-memory version
+                    await owner.repository.DeleteState(FlowID);
                 }
             }
 
@@ -150,20 +173,18 @@ namespace Tapeti.Flow.Default
                 if (flowLock == null)
                     throw new ObjectDisposedException("FlowStateLock");
 
-                if (flowState != null)
+                if (cachedFlowState != null)
                 {
-                    foreach (var removedContinuation in flowState.Continuations.Keys)
+                    foreach (var removedContinuation in cachedFlowState.FlowState.Continuations.Keys)
                         owner.continuationLookup.TryRemove(removedContinuation, out _);
 
-                    owner.flowStates.TryRemove(FlowID, out _);
+                    owner.flowStates.TryRemove(FlowID, out var removedFlowState);
+                    cachedFlowState = null;
 
-                    if (flowState != null)
+                    if (removedFlowState.IsPersistent)
-                    {
-                        flowState = null;
                         await owner.repository.DeleteState(FlowID);
                 }
             }
         }
     }
-    }
 }

Tapeti.Flow/IFlowStore.cs

@@ -52,7 +52,8 @@ namespace Tapeti.Flow
         /// Stores the new flow state.
         /// </summary>
         /// <param name="flowState"></param>
-        Task StoreFlowState(FlowState flowState);
+        /// <param name="persistent"></param>
+        Task StoreFlowState(FlowState flowState, bool persistent);
 
         /// <summary>
         /// Disposes of the flow state corresponding to this Flow ID.

Tapeti.Transient/TransientGenericBinding.cs

@@ -17,6 +17,9 @@ namespace Tapeti.Transient
         /// <inheritdoc />
         public string QueueName { get; private set; }
 
+        /// <inheritdoc />
+        public QueueType QueueType => QueueType.Dynamic;
+
 
         /// <inheritdoc />
         public TransientGenericBinding(TransientRouter router, string dynamicQueuePrefix)

Tapeti/Config/IBinding.cs

@@ -3,6 +3,23 @@ using System.Threading.Tasks;
 
 namespace Tapeti.Config
 {
+    /// <summary>
+    /// Determines the type of queue the binding registers
+    /// </summary>
+    public enum QueueType
+    {
+        /// <summary>
+        /// The consumed queue is durable
+        /// </summary>
+        Durable,
+
+        /// <summary>
+        /// The consumed queue is dynamic
+        /// </summary>
+        Dynamic
+    }
+
+
     /// <summary>
     /// Represents a registered binding to handle incoming messages.
     /// </summary>
@@ -14,6 +31,12 @@ namespace Tapeti.Config
         string QueueName { get; }
 
 
+        /// <summary>
+        /// Determines the type of queue the binding registers
+        /// </summary>
+        QueueType QueueType { get; }
+
+
         /// <summary>
         /// Called after a connection is established to set up the binding.
         /// </summary>

Tapeti/Default/ControllerMethodBinding.cs

@@ -83,6 +83,9 @@ namespace Tapeti.Default
         /// <inheritdoc />
         public string QueueName { get; private set; }
 
+        /// <inheritdoc />
+        public QueueType QueueType => bindingInfo.QueueInfo.QueueType;
+
         /// <inheritdoc />
         public Type Controller => bindingInfo.ControllerType;
 
@@ -106,7 +109,7 @@ namespace Tapeti.Default
             switch (bindingInfo.BindingTargetMode)
             {
                 case BindingTargetMode.Default:
-                    if (bindingInfo.QueueInfo.Dynamic)
+                    if (bindingInfo.QueueInfo.QueueType == QueueType.Dynamic)
                         QueueName = await target.BindDynamic(bindingInfo.MessageClass, bindingInfo.QueueInfo.Name);
                     else
                     {
@@ -117,7 +120,7 @@ namespace Tapeti.Default
                     break;
 
                 case BindingTargetMode.Direct:
-                    if (bindingInfo.QueueInfo.Dynamic)
+                    if (bindingInfo.QueueInfo.QueueType == QueueType.Dynamic)
                         QueueName = await target.BindDynamicDirect(bindingInfo.MessageClass, bindingInfo.QueueInfo.Name);
                     else
                     {
@@ -259,9 +262,9 @@ namespace Tapeti.Default
         public class QueueInfo
         {
             /// <summary>
-            /// Whether the queue is dynamic or durable.
+            /// The type of queue this binding consumes.
             /// </summary>
-            public bool Dynamic { get; set; }
+            public QueueType QueueType { get; set; }
 
             /// <summary>
             /// The name of the durable queue, or optional prefix of the dynamic queue.
@@ -272,7 +275,7 @@ namespace Tapeti.Default
             /// <summary>
             /// Determines if the QueueInfo properties contain a valid combination.
             /// </summary>
-            public bool IsValid => Dynamic|| !string.IsNullOrEmpty(Name);
+            public bool IsValid => QueueType == QueueType.Dynamic || !string.IsNullOrEmpty(Name);
         }
     }
 }

Tapeti/TapetiConfigControllers.cs

@@ -130,10 +130,10 @@ namespace Tapeti
                 throw new TopologyConfigurationException($"Cannot combine static and dynamic queue attributes on controller {member.DeclaringType?.Name} method {member.Name}");
 
             if (dynamicQueueAttribute != null)
-                return new ControllerMethodBinding.QueueInfo { Dynamic = true, Name = dynamicQueueAttribute.Prefix };
+                return new ControllerMethodBinding.QueueInfo { QueueType = QueueType.Dynamic, Name = dynamicQueueAttribute.Prefix };
 
             return durableQueueAttribute != null 
-                ? new ControllerMethodBinding.QueueInfo { Dynamic = false, Name = durableQueueAttribute.Name } 
+                ? new ControllerMethodBinding.QueueInfo { QueueType = QueueType.Durable, Name = durableQueueAttribute.Name } 
                 : null;
         }
     }