Given an Azure hosted Web Role with a highly-available WebAPI (say 99.95%, as per https://azure.microsoft.com/en-us/documentation/articles/resiliency-disaster-recovery-high-availability-azure-applications/) application that has ~1000 clients. Client is a ReactJS application. The WebAPI application will push notifications tailored to specific client groups (e.g. not all client users are interested in all events, but >1 user may be interested in the same event).
From reading the SignalR documentation and playing with some samples it feels like SignalR Groups will help us flow the right events to the right ReactJS application instances. Additionally we would use one of the SignalR scale out providers to make sure that the we push to the clients from the right WebAPI server instance.
Question: How do applications recover when the "right WebAPI" instance becomes unavailable?
I can imagine a server-side active/passive scheme with some complexity around making sure there is at least one 'server' for each Hub Client...but can a Server connect (in an unsolicited way) to a Hub Client? Would we have each Hub Client connect (when registering for a Group) to >1 Server?
How have applications solved this issue with SignalR?
I think I missed the obvious point that the scale-out providers and the back plane provide the very protection that clients need against servers that go-away. Clients don't connect to a specific server, but to a load-balanced name.