Activation repartitioner: use null for no-op message observer to avoid interface call

src/Orleans.Core/Networking/Connection.cs

@@ -353,7 +353,7 @@ private async Task ProcessOutgoing()
 
             Exception error = default;
             var serializer = this.shared.ServiceProvider.GetRequiredService<MessageSerializer>();
-            var messageStatisticsSink = this.shared.MessageStatisticsSink;
+            var messageObserver = this.shared.MessageStatisticsSink.GetMessageObserver();
             try
             {
                 var output = this._transport.Output;
@@ -375,7 +375,7 @@ private async Task ProcessOutgoing()
                             inflight.Add(message);
                             var (headerLength, bodyLength) = serializer.Write(output, message);
                             RecordMessageSend(message, headerLength + bodyLength, headerLength);
-                            messageStatisticsSink.RecordMessage(message);
+                            messageObserver?.Invoke(message);
                             message = null;
                         }
                     }

src/Orleans.Core/Placement/Repartitioning/IMessageStatisticsSink.cs

@@ -1,13 +1,15 @@
+#nullable enable
+using System;
 using Orleans.Runtime;
 
 namespace Orleans.Placement.Repartitioning;
 
 internal interface IMessageStatisticsSink
 {
-    void RecordMessage(Message message);
+    Action<Message>? GetMessageObserver();
 }
 
 internal sealed class NoOpMessageStatisticsSink : IMessageStatisticsSink
 {
-    public void RecordMessage(Message message) { }
+    public Action<Message>? GetMessageObserver() => null;
 }

src/Orleans.Runtime/Hosting/DefaultSiloServices.cs

@@ -138,7 +138,7 @@ internal static void AddDefaultServices(ISiloBuilder builder)
             services.TryAddSingleton<MessageCenter>();
             services.TryAddFromExisting<IMessageCenter, MessageCenter>();
             services.TryAddSingleton(FactoryUtility.Create<MessageCenter, Gateway>);
-            services.TryAddSingleton<IConnectedClientCollection>(sp => (IConnectedClientCollection)sp.GetRequiredService<MessageCenter>().Gateway ?? new EmptyConnectedClientCollection());
+            services.TryAddSingleton<IConnectedClientCollection>(sp => sp.GetRequiredService<MessageCenter>().Gateway as IConnectedClientCollection ?? new EmptyConnectedClientCollection());
             services.TryAddSingleton<InternalGrainRuntime>();
             services.TryAddSingleton<InsideRuntimeClient>();
             services.TryAddFromExisting<IRuntimeClient, InsideRuntimeClient>();

src/Orleans.Runtime/Messaging/MessageCenter.cs

@@ -1,3 +1,4 @@
+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -22,12 +23,12 @@ internal class MessageCenter : IMessageCenter, IAsyncDisposable
         private readonly SiloMessagingOptions messagingOptions;
         private readonly PlacementService placementService;
         private readonly GrainLocator _grainLocator;
-        private readonly IMessageStatisticsSink _messageStatisticsSink;
+        private readonly Action<Message>? _messageObserver;
         private readonly ILogger log;
         private readonly Catalog catalog;
         private bool stopped;
-        private HostedClient hostedClient;
-        private Action<Message> sniffIncomingMessageHandler;
+        private HostedClient? hostedClient;
+        private Action<Message>? sniffIncomingMessageHandler;
 
         public MessageCenter(
             ILocalSiloDetails siloDetails,
@@ -50,7 +51,7 @@ public MessageCenter(
             this.messagingTrace = messagingTrace;
             this.placementService = placementService;
             _grainLocator = grainLocator;
-            _messageStatisticsSink = messageStatisticsSink;
+            _messageObserver = messageStatisticsSink.GetMessageObserver();
             this.log = logger;
             this.messageFactory = messageFactory;
             this._siloAddress = siloDetails.SiloAddress;
@@ -61,19 +62,19 @@ public MessageCenter(
             }
         }
 
-        public Gateway Gateway { get; }
+        public Gateway? Gateway { get; }
 
         internal bool IsBlockingApplicationMessages { get; private set; }
 
-        public void SetHostedClient(HostedClient client) => this.hostedClient = client;
+        public void SetHostedClient(HostedClient? client) => this.hostedClient = client;
 
         public bool TryDeliverToProxy(Message msg)
         {
             if (!msg.TargetGrain.IsClient()) return false;
             if (this.Gateway is Gateway gateway && gateway.TryDeliverToProxy(msg)
                 || this.hostedClient is HostedClient client && client.TryDispatchToClient(msg))
             {
-                _messageStatisticsSink.RecordMessage(msg);
+                _messageObserver?.Invoke(msg);
                 return true;
             }
 
@@ -125,7 +126,7 @@ public async Task StopAcceptingClientMessages()
             }
         }
 
-        public Action<Message> SniffIncomingMessage
+        public Action<Message>? SniffIncomingMessage
         {
             set
             {
@@ -251,8 +252,8 @@ static async Task SendAsync(MessageCenter messageCenter, ValueTask<Connection> c
         public void RejectMessage(
             Message message,
             Message.RejectionTypes rejectionType,
-            Exception exc,
-            string rejectInfo = null)
+            Exception? exc,
+            string? rejectInfo = null)
         {
             if (message.Direction == Message.Directions.Request
                 || (message.Direction == Message.Directions.OneWay && message.HasCacheInvalidationHeader))
@@ -271,20 +272,20 @@ public void RejectMessage(
 
         internal void ProcessRequestsToInvalidActivation(
             List<Message> messages,
-            GrainAddress oldAddress,
-            SiloAddress forwardingAddress,
-            string failedOperation = null,
-            Exception exc = null,
+            GrainAddress? oldAddress,
+            SiloAddress? forwardingAddress,
+            string? failedOperation = null,
+            Exception? exc = null,
             bool rejectMessages = false)
         {
             if (rejectMessages)
             {
-                GrainAddress validAddress = forwardingAddress switch
+                GrainAddress? validAddress = forwardingAddress switch
                 {
                     null => null,
                     _ => new()
                     {
-                        GrainId = oldAddress.GrainId,
+                        GrainId = oldAddress?.GrainId ?? default,
                         SiloAddress = forwardingAddress,
                     }
                 };
@@ -304,12 +305,12 @@ internal void ProcessRequestsToInvalidActivation(
             else
             {
                 this.messagingTrace.OnDispatcherForwardingMultiple(messages.Count, oldAddress, forwardingAddress, failedOperation, exc);
-                GrainAddress destination = forwardingAddress switch
+                GrainAddress? destination = forwardingAddress switch
                 {
                     null => null,
                     _ => new()
                     {
-                        GrainId = oldAddress.GrainId,
+                        GrainId = oldAddress?.GrainId ?? default,
                         SiloAddress = forwardingAddress,
                     }
                 };
@@ -323,10 +324,10 @@ internal void ProcessRequestsToInvalidActivation(
 
         private void ProcessRequestToInvalidActivation(
             Message message,
-            GrainAddress oldAddress,
-            SiloAddress forwardingAddress,
+            GrainAddress? oldAddress,
+            SiloAddress? forwardingAddress,
             string failedOperation,
-            Exception exc = null,
+            Exception? exc = null,
             bool rejectMessages = false)
         {
             Debug.Assert(!message.IsLocalOnly);
@@ -344,20 +345,20 @@ private void ProcessRequestToInvalidActivation(
             }
             else
             {
-                GrainAddress destination = forwardingAddress switch
+                GrainAddress? destination = forwardingAddress switch
                 {
                     null => null,
                     _ => new()
                     {
-                        GrainId = oldAddress.GrainId,
+                        GrainId = oldAddress?.GrainId ?? default,
                         SiloAddress = forwardingAddress,
                     }
                 };
                 this.TryForwardRequest(message, oldAddress, destination, failedOperation, exc);
             }
         }
 
-        private void TryForwardRequest(Message message, GrainAddress oldAddress, GrainAddress destination, string failedOperation = null, Exception exc = null)
+        private void TryForwardRequest(Message message, GrainAddress? oldAddress, GrainAddress? destination, string? failedOperation = null, Exception? exc = null)
         {
             Debug.Assert(!message.IsLocalOnly);
 
@@ -415,7 +416,7 @@ internal void RerouteMessage(Message message)
             ResendMessageImpl(message);
         }
 
-        private bool TryForwardMessage(Message message, SiloAddress forwardingAddress)
+        private bool TryForwardMessage(Message message, SiloAddress? forwardingAddress)
         {
             if (!MayForward(message, this.messagingOptions)) return false;
 
@@ -425,7 +426,7 @@ private bool TryForwardMessage(Message message, SiloAddress forwardingAddress)
             return true;
         }
 
-        private void ResendMessageImpl(Message message, SiloAddress forwardingAddress = null)
+        private void ResendMessageImpl(Message message, SiloAddress? forwardingAddress = null)
         {
             if (log.IsEnabled(LogLevel.Debug)) log.LogDebug("Resend {Message}", message);
 
@@ -543,7 +544,7 @@ public void ReceiveMessage(Message msg)
                     }
 
                     targetActivation.ReceiveMessage(msg);
-                    _messageStatisticsSink.RecordMessage(msg);
+                    _messageObserver?.Invoke(msg);
                 }
             }
             catch (Exception ex)

src/Orleans.Runtime/Placement/Repartitioning/ActivationRepartitioner.MessageSink.cs

@@ -1,6 +1,7 @@
 #nullable enable
 using System;
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
@@ -109,7 +110,9 @@ private async Task ProcessPendingEdges(CancellationToken cancellationToken)
         }
     }
 
-    public void RecordMessage(Message message)
+    public Action<Message>? GetMessageObserver() => RecordMessage;
+
+    private void RecordMessage(Message message)
     {
         if (!_enableMessageSampling || message.IsSystemMessage)
         {

src/Orleans.Runtime/Placement/Repartitioning/RepartitionerMessageFilter.cs

@@ -1,5 +1,4 @@
 #nullable enable
-using Orleans;
 using Orleans.Metadata;
 using System;
 using System.Collections.Concurrent;