Refactor other use of ConcurrentDictionary GetOrAdd

Author: lukebakken

projects/RabbitMQ.Client/client/impl/AsyncConsumerWorkService.cs

@@ -8,14 +8,8 @@ namespace RabbitMQ.Client.Impl
 {
     internal sealed class AsyncConsumerWorkService : ConsumerWorkService
     {
-        private readonly ConcurrentDictionary<IModel, WorkPool> _workPools;
-        private readonly Func<IModel, WorkPool> _startNewWorkPoolFunc;
-
-        public AsyncConsumerWorkService()
-        {
-            _workPools = new ConcurrentDictionary<IModel, WorkPool>();
-            _startNewWorkPoolFunc = model => StartNewWorkPool(model);
-        }
+        private readonly ConcurrentDictionary<IModel, WorkPool> _workPools = new ConcurrentDictionary<IModel, WorkPool>();
+        private readonly Func<IModel, WorkPool> _startNewWorkPoolFunc = model => StartNewWorkPool(model);
 
         public void Schedule<TWork>(ModelBase model, TWork work) where TWork : Work
         {
@@ -25,10 +19,14 @@ public void Schedule<TWork>(ModelBase model, TWork work) where TWork : Work
              *
              * The lock is necessary because calling the value delegate is not atomic.
              */
+            WorkPool workPool;
+
             lock (_workPools)
             {
-                _workPools.GetOrAdd(model, _startNewWorkPoolFunc).Enqueue(work);
+                workPool = _workPools.GetOrAdd(model, _startNewWorkPoolFunc);
             }
+
+            workPool.Enqueue(work);
         }
 
         private static WorkPool StartNewWorkPool(IModel model)

projects/RabbitMQ.Client/client/impl/ConsumerWorkService.cs

@@ -8,13 +8,27 @@ namespace RabbitMQ.Client.Impl
     class ConsumerWorkService
     {
         private readonly ConcurrentDictionary<IModel, WorkPool> _workPools = new ConcurrentDictionary<IModel, WorkPool>();
+        private readonly Func<IModel, WorkPool> _startNewWorkPoolFunc = model => StartNewWorkPool(model);
 
         public void AddWork(IModel model, Action fn)
         {
-            _workPools.GetOrAdd(model, StartNewWorkPool).Enqueue(fn);
+            /*
+             * rabbitmq/rabbitmq-dotnet-client#841
+             * https://docs.microsoft.com/en-us/dotnet/api/system.collections.concurrent.concurrentdictionary-2.getoradd
+             *
+             * The lock is necessary because calling the value delegate is not atomic.
+             */
+            WorkPool workPool;
+
+            lock (_workPools)
+            {
+                workPool = _workPools.GetOrAdd(model, _startNewWorkPoolFunc);
+            }
+
+            workPool.Enqueue(fn);
         }
 
-        private WorkPool StartNewWorkPool(IModel model)
+        private static WorkPool StartNewWorkPool(IModel model)
         {
             var newWorkPool = new WorkPool();
             newWorkPool.Start();