Fix the ack message issue when MapHub for the same hub is called mult…

…iple times (#2021)

* Fix the ack message issue when MapHub for the same hub is called multiple times

* Update ServiceConnectionContainerBase.cs

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

@@ -113,7 +113,10 @@ protected ServiceConnectionContainerBase(IServiceConnectionFactory serviceConnec
  Logger = logger ?? throw new ArgumentNullException(nameof(logger));
  ServiceConnectionFactory = serviceConnectionFactory;
  Endpoint = endpoint;
- _ackHandler = ackHandler ?? new AckHandler();
+ // use globally unique AckHanlder if not specified
+ // It is possible that the multiple MapHub calls the same hub, so that ack messages could be received by another instance of ServiceConnectionContainer
+ // Use the ack handler singleton to allow ack message to be acked by another container instance
+ _ackHandler = ackHandler ?? AckHandler.Singleton;
 
  // make sure it is after _endpoint is set
  // init initial connections

src/Microsoft.Azure.SignalR.Common/Utilities/AckHandler.cs

@@ -11,6 +11,7 @@ namespace Microsoft.Azure.SignalR
 {
  internal sealed class AckHandler : IDisposable
  {
+ public static readonly AckHandler Singleton = new();
  private readonly ConcurrentDictionary<int, IAckInfo> _acks = new();
  private readonly Timer _timer;
  private readonly TimeSpan _defaultAckTimeout;