Trying to fix #91 race conditions

and NullReferenceException logs in AsyncWampConnection.

Author: Elad Zelingher

src/net45/WampSharp/Core/Listener/Connections/AsyncConnection/AsyncWampConnection.cs

@@ -27,46 +27,64 @@ public void Send(WampMessage<object> message)
 
         protected async Task InnerSend(WampMessage<object> message)
         {
+            const string errorMessage = 
+                "An error occured while attempting to send a message to remote peer.";
+
             if (IsConnected)
             {
                 try
                 {
                     Task sendAsync = SendAsync(message);
 
-                    await sendAsync.ConfigureAwait(false);
+                    if (sendAsync != null)
+                    {
+                        await sendAsync.ConfigureAwait(false);
+                    }
+                    else
+                    {
+                        mLogger.Error(errorMessage + " Got null Task.");
+                    }
                 }
                 catch (Exception ex)
                 {
-                    mLogger.Error("An error occured while attempting to send a message to remote peer.", ex);
+                    mLogger.Error(errorMessage, ex);
                 }
             }
         }
 
 #else
         protected Task InnerSend(WampMessage<object> message)
         {
+            const string errorMessage =
+                "An error occured while attempting to send a message to remote peer.";
+
             if (IsConnected)
             {
                 Task sendAsync = SendAsync(message);
-                
-                Task result = sendAsync.ContinueWith(task =>
-                {
-                    var ex = task.Exception;
 
-                    if (ex != null)
+                if (sendAsync == null)
+                {
+                    mLogger.Error(errorMessage + " Got null Task.");
+                }
+                else
+                {
+                    Task result = sendAsync.ContinueWith(task =>
                     {
-                        mLogger.Error("An error occured while attempting to send a message to remote peer.", ex);                        
-                    }
-                });
-                
-                return result;
-            }
-            else
-            {
-                TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
-                tcs.SetResult(null);
-                return tcs.Task;
+                        var ex = task.Exception;
+
+                        if (ex != null)
+                        {
+                            mLogger.Error(errorMessage, ex);
+                        }
+                    });
+
+                    return result;
+                }
             }
+
+            TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
+            tcs.SetResult(null);
+            return tcs.Task;
         }
 
 #endif

src/net45/WampSharp/Core/Utilities/DictionaryExtensions.cs

@@ -1,10 +1,31 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 
 namespace WampSharp.Core.Utilities
 {
     internal static class DictionaryExtensions
     {
+        public static bool TryRemoveExact<TKey, TValue>
+            (this ConcurrentDictionary<TKey, TValue> dictionary,
+             TKey key,
+             TValue value)
+        {
+            bool result = false;
+            TValue dictionaryValue;
+
+            if (dictionary.TryGetValue(key, out dictionaryValue))
+            {
+                if (object.ReferenceEquals(dictionaryValue, value))
+                {
+                    TValue removed;
+                    result = dictionary.TryRemove(key, out removed);
+                }
+            }
+
+            return result;
+        }
+
         public static bool Remove<TKey, TValue>(this IDictionary<TKey, ICollection<TValue>> dictionary,
                                                 TKey key,
                                                 TValue value)

src/net45/WampSharp/Core/Utilities/IdMapperBase.cs

@@ -34,6 +34,11 @@ public bool TryRemove(TKey id, out T value)
             return mIdToValue.TryRemove(id, out value);
         }
 
+        public bool TryRemoveExact(TKey id, T value)
+        {
+            return mIdToValue.TryRemoveExact(id, value);
+        }
+
         public void Clear()
         {
             mIdToValue.Clear();

src/net45/WampSharp/WAMP2/V2/PubSub/MatchTopicContainer.cs

@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using WampSharp.Core.Serialization;
+using WampSharp.Core.Utilities;
 using WampSharp.V2.Core.Contracts;
 
 namespace WampSharp.V2.PubSub
@@ -184,15 +185,14 @@ private void OnTopicEmpty(object sender, EventArgs e)
         {
             lock (mLock)
             {
-                IWampTopic topic = sender as IWampTopic;
+                WampTopic topic = sender as WampTopic;
 
                 if (!topic.HasSubscribers)
                 {
                     topic.TopicEmpty -= OnTopicEmpty;
                     topic.Dispose();
 
-                    IWampTopic deletedTopic;
-                    TryRemoveTopicByUri(topic.TopicUri, out deletedTopic);
+                    mTopicUriToSubject.TryRemoveExact(topic.TopicUri, topic);
                 }
             }
         }

src/net45/WampSharp/WAMP2/V2/PubSub/WampRawTopicContainer.cs

@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
+using WampSharp.Core.Utilities;
 using WampSharp.V2.Binding;
 using WampSharp.V2.Core;
 using WampSharp.V2.Core.Contracts;
@@ -96,8 +97,8 @@ private void OnTopicEmpty(object sender, EventArgs e)
                 {
                     if (!rawTopic.HasSubscribers)
                     {
-                        mSubscriptionIdToTopic.TryRemove(rawTopic.SubscriptionId, out rawTopic);
-                        mTopicUriToTopic.TryRemove(rawTopic.CustomizedSubscriptionId, out rawTopic);
+                        mSubscriptionIdToTopic.TryRemoveExact(rawTopic.SubscriptionId, rawTopic);
+                        mTopicUriToTopic.TryRemoveExact(rawTopic.CustomizedSubscriptionId, rawTopic);
                         rawTopic.Dispose();
                     }
                 }

src/net45/WampSharp/WAMP2/V2/Rpc/Dealer/MatchRpcOperationCatalog.cs

@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using WampSharp.Core.Serialization;
+using WampSharp.Core.Utilities;
 using WampSharp.V2.Core;
 using WampSharp.V2.Core.Contracts;
 
@@ -69,9 +70,8 @@ private void OnRegistrationEmpty(object sender, EventArgs e)
                 {
                     if (!registration.HasOperations)
                     {
-                        ProcedureRegistration removed;
-                        mRegistrationIdToRegistration.TryRemove(registration.RegistrationId, out removed);
-                        mProcedureToRegistration.TryRemove(registration.Procedure, out removed);
+                        mRegistrationIdToRegistration.TryRemoveExact(registration.RegistrationId, registration);
+                        mProcedureToRegistration.TryRemoveExact(registration.Procedure, registration);
                         registration.Empty -= OnRegistrationEmpty;
                         OnRegistrationRemoved(registration.Procedure);
                     }