SignalR - SSE/LongPoll Close connection returns 404

[omorsky-pcor]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Client - signalR 8.0.0 (typescript/browser)
Server - 8.0.4

I have a browser client that connect to SignalR hub via Server-Sent events (My reverse proxy does not support websockets)
The communication works well.

1. Client connects
2. Sends some data via invoke function
3. Once all data is transfered the client calls connection.stop(), which generates POST request to a hub with 404/No Connection with that ID response
4. It seems that the server successfully closes the connection but returns 404 with

Server logs from close call:

[11:51:38.482 INF] Microsoft.AspNetCore.Hosting.Diagnostics - Request starting HTTP/2 POST https://localhost:56480/hubs/plansExport?id=njAzClV6o81z9cB3kHElpg - text/plain;charset=UTF-8 11
[11:51:38.488 DBG] Microsoft.AspNetCore.Routing.Matching.DfaMatcher - 2 candidate(s) found for the request path '/hubs/plansExport'
[11:51:38.510 DBG] Microsoft.AspNetCore.Routing.Matching.DfaMatcher - Endpoint '/hubs/plansExport' with route pattern '/hubs/plansExport' is valid for the request path '/hubs/plansExport'
[11:51:40.829 DBG] Microsoft.AspNetCore.Routing.Matching.DfaMatcher - Endpoint 'Fallback {*path:nonfile}' with route pattern '{*path:nonfile}' is valid for the request path '/hubs/plansExport'
[11:51:40.845 DBG] Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware - Request matched endpoint '/hubs/plansExport'
[11:51:40.970 DBG] Microsoft.AspNetCore.SignalR.HubConnectionHandler - OnConnectedAsync ending.
[11:51:41.844 DBG] Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionManager - Removing connection njAzClV6o81z9cB3kHElpg from the list of connections.
[11:51:41.853 INF] Microsoft.AspNetCore.Routing.EndpointMiddleware - Executing endpoint '/hubs/plansExport'
[11:51:41.863 INF] Microsoft.AspNetCore.Routing.EndpointMiddleware - Executed endpoint '/hubs/plansExport'
[11:51:42.627 INF] Microsoft.AspNetCore.Hosting.Diagnostics - Request finished HTTP/2 GET https://localhost:56480/hubs/plansExport?id=njAzClV6o81z9cB3kHElpg - 200 null text/event-stream 12650.3697ms
[11:51:42.627 INF] Microsoft.AspNetCore.Routing.EndpointMiddleware - Executed endpoint '/hubs/plansExport'
[11:51:42.671 INF] Microsoft.AspNetCore.Hosting.Diagnostics - Request finished HTTP/2 POST https://localhost:56480/hubs/plansExport?id=njAzClV6o81z9cB3kHElpg - 404 null text/plain 4188.9645ms

In logs I can see

• 11:51:38.482 Close request starting

• 11:51:41.844 Connection removed

• 11:51:42.627 SSE connection closed

• 11:51:42.671 Close request finished with 404

• My hub url has a custom query parameter but removing it does not seem to make any change

• I have multiple server instances, but the communication works well except the close call

• The same happens when using Long-Poll

• The same happens with other versions on client/server

• The app is running in linux/docker in production and the same happens when debugging locally with Windows

There is no visible issue for a users, The only thing is that this 404 generates Failed to Fetch exception + error log which gets collected by a monitoring tools in both client and server.

Possibly related issues:

• #5350
• #27584

Expected Behavior

Close connection should return 2xx if there is no error.

Steps To Reproduce

I am not able to reproduce it on small/new project.
My application is pretty big. I tried removing all code that is not needed and all middlewares except the minimal needed ones (authorization, session, routing, ...) but the issue still occurs

EDIT: I somehow managed to reporoduce it - https://github.com/omorsky-pcor/signalr_close_404
It returns 404 randomly (about 1 out of 10 close calls) with empty content.
The No Connection with that ID is even less frequent

Exceptions (if any)

No response

.NET Version

8.0.4

Anything else?

No response