fix: [#6683] Timeout issue when using DLASE (#6696)

* Add Http 202 (Accepted) for DLASE

* Fix unit tests

libraries/Microsoft.Bot.Connector.Streaming/Session/StreamingSession.cs

@@ -7,6 +7,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Runtime.InteropServices;
 using System.Text.Json;
 using System.Threading;
@@ -91,7 +92,7 @@ public async Task<ReceiveResponse> SendRequestAsync(StreamingRequest request, Ca
  }
  }
 
- return await responseCompletionSource.Task.DefaultTimeOutAsync().ConfigureAwait(false); 
+ return await responseCompletionSource.Task.DefaultTimeOutAsync().ConfigureAwait(false);
  }
 
  public async Task SendResponseAsync(Header header, StreamingResponse response, CancellationToken cancellationToken)
@@ -194,6 +195,11 @@ public virtual void ReceiveResponse(Header header, ReceiveResponse response)
 
  Log.PayloadReceived(_logger, header);
 
+ if (response.StatusCode == (int)HttpStatusCode.Accepted)
+ {
+ return;
+ }
+
  lock (_receiveSync)
  {
  if (!response.Streams.Any())
@@ -358,6 +364,8 @@ private void ProcessRequest(Guid id, ReceiveRequest request)
  {
  _ = Task.Run(async () =>
  {
+ // Send an HTTP 202 (Accepted) response right away, otherwise, while under high streaming load, the conversation times out due to not having a response in the request/response time frame.
+ await SendResponseAsync(new Header { Id = id, Type = PayloadTypes.Response }, new StreamingResponse { StatusCode = (int)HttpStatusCode.Accepted }, _connectionCancellationToken).ConfigureAwait(false);
  var streamingResponse = await _receiver.ProcessRequestAsync(request, null).ConfigureAwait(false);
  await SendResponseAsync(new Header() { Id = id, Type = PayloadTypes.Response }, streamingResponse, _connectionCancellationToken).ConfigureAwait(false);
 

libraries/Microsoft.Bot.Streaming/ProtocolAdapter.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System;
+using System.Net;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -75,6 +76,11 @@ private async Task OnReceiveRequestAsync(Guid id, ReceiveRequest request)
 
  private async Task OnReceiveResponseAsync(Guid id, ReceiveResponse response)
  {
+ if (response.StatusCode == (int)HttpStatusCode.Accepted)
+ {
+ return;
+ }
+
  // we received the response to something, signal it
  await _requestManager.SignalResponseAsync(id, response).ConfigureAwait(false);
  }