SignalR, No Connection with that ID

I have an asp.net core app that uses SignalR to report metrics that are visualized in the browser. It has been working fine for several weeks, but today I noticed that SignalR fails to connect very often and even when it connects, it disconnect shortly after. I’m using LongPolling and I can see in the network logs of Chrome that the first request to “negotiate” is always successful.

{"connectionId":"Vg4Mieg0ya3aD17-f8kMxw","availableTransports":[{"transport":"LongPolling","transferFormats":["Text","Binary"]}]}

but the second one which is a POST to “notify” is not (49 out of 50 times) and it responds with 404 Not found.

No Connection with that ID

I sometimes get the following as well.

{"error":"Handshake was canceled."}

The app works flawlessly when hosted locally (using localhost). It only happens when the app is hosted (IT/FT/…) in Azure as a Web App Service and all the resources of the application are downloaded successfully. I have the above issues only for SignalR requests from browser and logs on the server side don’t show anything wrong. Target framework: .NET Core 2.2

[analogrelay]

@mathiassiig I’d strongly advise you to create a new issue with your specific scenario. Since this is a closed issue, it doesn’t come up in our regular tracking so you’re relying on David and I alone paying attention to our GitHub notifications (which we generally do, but can easily get behind on 😉).

[zeroregard]

It’s an Azure Web App running ASP.NET Core with the newest version of SignalR. I increased the timeout intervals, but it didn’t seem to do a difference. It happens randomly, although there seems to be periods where it happens several times in a row.