Partial support client results in sharding mode.

specs/ClientInvocation.md

@@ -62,9 +62,11 @@ Basically the process is similar and the major different is that service underst
 
 ### Transient Mode(TODO)
 
+## Limitations
+
 > NOTES
 > 
 > * Service cached pending invocations for at most __10 minutes__ for memory concerns and will notify server when timeout.
 > * Serverless is __NOT__ supporeted in the first stage.
 > * ASPNET SignalR is __NOT__ supported.
-> * Sharding is __NOT__ supported. Please use [Geo-Replication](https://learn.microsoft.com/azure/azure-signalr/howto-enable-geo-replication) for combined client invocation and large scale scenarios.
+> * Sharding is __NOT__ fully supported yet. Please use [Geo-Replication](https://learn.microsoft.com/azure/azure-signalr/howto-enable-geo-replication) for combined client invocation and large scale scenarios. Also see [this](https://github.com/Azure/azure-signalr/pull/1828) for planning.

src/Microsoft.Azure.SignalR.Common/ServiceConnections/MultiEndpointServiceConnectionContainer.cs

@@ -230,6 +230,15 @@ internal IEnumerable<ServiceEndpoint> GetRoutedEndpoints(ServiceMessage message)
                 case CloseConnectionMessage closeConnectionMessage:
                     return _router.GetEndpointsForConnection(closeConnectionMessage.ConnectionId, endpoints);
 
+                case ClientInvocationMessage clientInvocationMessage:
+                    return SingleOrNotSupported(_router.GetEndpointsForConnection(clientInvocationMessage.ConnectionId, endpoints), clientInvocationMessage);
+
+                case ServiceMappingMessage serviceMappingMessage:
+                    return SingleOrNotSupported(_router.GetEndpointsForConnection(serviceMappingMessage.ConnectionId, endpoints), serviceMappingMessage);
+
+                case ServiceCompletionMessage serviceCompletionMessage:
+                    return SingleOrNotSupported(_router.GetEndpointsForConnection(serviceCompletionMessage.ConnectionId, endpoints), serviceCompletionMessage);
+
                 default:
                     throw new NotSupportedException(message.GetType().Name);
             }
@@ -416,6 +425,20 @@ private async Task WaitForClientsDisconnect(HubServiceEndpoint endpoint)
             Log.TimeoutWaitingClientsDisconnect(_logger, endpoint.ToString(), (int)_scaleTimeout.TotalSeconds);
         }
 
+        private IEnumerable<ServiceEndpoint> SingleOrNotSupported(IEnumerable<ServiceEndpoint> endpoints, ServiceMessage message)
+        {
+            var endpointCnt = endpoints.ToList().Count;
+            if (endpointCnt == 1)
+            {
+                return endpoints;
+            }
+            if (endpointCnt == 0)
+            {
+                throw new ArgumentException("Client invocation is not sent because no endpoint is returned from the endpoint router.");
+            }
+            throw new NotSupportedException("Client invocation to wait for multiple endpoints' results is not supported yet.");
+        }
+
         internal static class Log
         {
             private static readonly Action<ILogger, string, Exception> _startingConnection =