SignalR how to reconnect with same connectionId

[quytrieu37]

Hi everyone, my question is related to signalR.
I have a long-running task on Hub and after it is complete, the hub will send a response base on Clients.Caller.SendAsync method
But currently, while running, it look like that hub doesn't send keep-alive message to client and after ServerTimeout (default is 30s), the connection will timeout and reconnect cause I config WithAutomaticReconnect() on client.
But when after reconnecting, the connection comes with difference connectionId so it can't listen to messages from server which send to old connectionId
I understand that there are Groups and Users to handle this scenario, but perhaps there is an alternative approach to retaining the connection ID after reconnecting?
Thank you!

[davidfowl]

https://learn.microsoft.com/en-us/aspnet/core/release-notes/aspnetcore-8.0?view=aspnetcore-8.0#signalr-stateful-reconnect

[achalrajpoot1]

@davidfowl I shared the details as above . Could you please have a look ?

[davidfowl]

cc @BrennanConroy

[achalrajpoot1]

@davidfowl @BrennanConroy I am blocked as of now for the reconnect implementation. I would request you please have a look on this issue. Thank you .

[BrennanConroy]

What are you blocked by? Stateful reconnect is not a guarantee that clients will reconnect with the same ID. It is a best effort attempt (and that effort may change/improve in future versions) and if your application is relying on the server maintaining state for clients across reconnects then you need to implement that logic yourself.

[Mise22]

I also can't get stateful reconnect to work, is there a code sample with the js client of this working?

In NegotiationResponse.cs it is suggested that the client should handle connectionId preservation:
"UseStatefulReconnect -> If set, the connection should attempt to reconnect with the same ConnectionId if it disconnects."

Looking at the client source (HubConnection.ts/HttpConnection.ts) I see no code preserving the connection id (this.connectionId = undefined; is called before reconnect), is this done in a different way?

I have enabled withAutomaticReconnect() because without it there is no reconnection at all (also looking at the code). In the docs it is unclear if it should be enabled to use withStatefulReconnect(), it looked to me like it is a parallel feature https://learn.microsoft.com/en-us/aspnet/core/release-notes/aspnetcore-8.0?view=aspnetcore-8.0#signalr-stateful-reconnect

[co-dax]

As a workaround you should be able to use IUserIdProvider and send the message to the specific client by using the "SignalR UserId" you returned from IUserIdProvider.GetUserId(HubConnectionContext connection). That way you would send the message to the client by using the SignalR UserId that has been generated by you (so you always know its value) instead of having to rely on SignalR connectionId. If you use IUserIdProvider.GetUserId(HubConnectionContext connection) then SignalR will automatically and internally link the SignalR UserId you returned from it to the SignalR connectionId.

[jonesr-out]

Hi @BrennanConroy, I have also been unable to get stateful re-connect to work as far as I understand it should work.

I have setup a sample here

The steps I am using to work with the sample are as follows:

1. Start the solution which should fire up the aspnet core server and angular client
2. When the client loads you should start seeing a counter incrementing, this counter is being pushed to the client via a hosted service which sends messages to a group using the hub context.
3. I disable networking using the dev tools and wait for the signalr connection to close.
4. When I enable networking again I am expecting any messages which I did not receive while in the disconnected state to be received, which does not seem to be the case. You can see in the screen shot below that I did not receive a number of counter messages once the connection re-established.

Please can you confirm if there is something which I have done incorrectly, or if my expectations of how this feature works is incorrect.

Thanks in advance!