Add comments to describe why we retry

Signed-off-by: halspang <[email protected]>

Author: halspang

src/Worker/Grpc/GrpcDurableTaskWorker.Processor.cs

@@ -67,7 +67,12 @@ public async Task ExecuteAsync(CancellationToken cancellation)
                 }
                 catch (RpcException ex) when (ex.StatusCode == StatusCode.NotFound)
                 {
-                    // Task hub is not found or insufficient permissions - retry
+                    // We retry on a NotFound for several reasons:
+                    // 1. It was the existing behavior through the UnexpectedError path.
+                    // 2. A 404 can be returned for a missing task hub or authentication failure. Authentication takes
+                    //    time to propagate so we should retry instead of making the user restart the application.
+                    // 3. In some cases, a task hub can be created separately from the scheduler. If a worker is deployed
+                    //    between the scheduler and task hub, it would need to be restarted to function.
                     this.Logger.TaskHubNotFound();
                 }
                 catch (OperationCanceledException) when (cancellation.IsCancellationRequested)