Can't reason why a custom SignalR Hub get created two times when a user does not log in.

[aaronamm]

Hello everyone.
During debugging my project I found something interesting for a project that uses SignalR.
If a user does not log in to a website, a custom SignalR Hub is created two times after starting a SignalR connection.

If a custom Hub has an overridden OnConnectedAsync method, it is called on second instance.

On the other hand, if a user has logged in to a website, a custom hub is created only one instance and OnConnectedAsync is called immediately.

Here is the simple project to reproduce this behavior.
https://github.com/aaronamm/aspnetcore-signalr-sample/blob/develop/PingHub.cs#L7

I tried to figure it out and reason why a custom hub get created two times when a user does not log in.
https://github.com/dotnet/aspnetcore/blob/main/src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs#L104

However, I still can't reason about it. There must be some logic to check if a user has logged in or other checking logic but I couldn't find it.

If someone is familiar with this area, please let me know why a custom hub get created two times when a user does not log in.

Thank you.

[BrennanConroy]

https://learn.microsoft.com/aspnet/core/signalr/hubs?view=aspnetcore-9.0#create-and-use-hubs

Hubs are transient:

[aaronamm]

@BrennanConroy thank you so much for a prompt reply.
I think I ran into this document before.
That's information is very helpful for managing hub and its dependencies.

However, I still don't understand why a hub get created two times when a user does not log in and created only one time when a user log in.

[aaronamm]

It is not about a user log in or not.
If we reload a page that has SignalR, there are two SignalR hubs get create because of the following scenario:

If there is a connected connection, a SigalR hub get created from DefaultHubDispatcher<THub>.OnConnectedAsync.
https://github.com/dotnet/aspnetcore/blob/main/src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs#L124

Then a new connection is started. A new SignalR hub get created from DefaultHubDispatcher<THub>.OnConnectedAsync and hub.ConnectedAsync method get called.

https://github.com/dotnet/aspnetcore/blob/main/src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs#L88