Adding Azure SignalR Service to Pointing Party

For a while I’ve hosted a small scale Blazor application to help my team with so called planning poker sessions. This went through some iterations, starting out as a Blazor Server application, and moving to a Blazor WebAssembly when Blazor Server turned out to be too cumbersome for mobile users.

The Blazor WebAssembly experience has been pretty great. The application runs on a single fly.io instance which distributes updates to the WASM clients over SignalR websockets. Unfortunately, there have been strange issues with SignalR that had me looking for other solutions. I quickly realised that Azure SignalR Service should be my first experiment, since it promises to handle scaing grafecully. Azure SignalR Service has a free tier that allows up to 20 concurrent connections, which was sufficient for my fledgling application, so I give it a shot.

To use SignalR service, your application doesn’t even have to run on Azure. You can authorize using an API key when using the service from outside Azure. To configure the Blazor Web App, all that’s needed is adding the Microsoft.Azure.SignalR NuGet package and this single line of code:

builder.Services.AddSignalR().AddAzureSignalR(options => options.InitialHubServerConnectionCount = 1);

By limiting the InitialHubServerConnectionCount, we ensure that only one connection is established between the backend and the Azure SignalR Service. This leaves 19 connections for our clients. That’s all! Clients are automatically redirected to the Azure SignalR Service and traffic between the backend and the Azure SignalR Service is multiplexed automatically.

Perceived performance of the application improved immediately. Gone were the remaining SignalR stability issues and there was no noticable impact on latency. So while it’s a shame that SignalR locks you in to this single Azure service, I have to say the service itself is good, pretty pretty good and I’m happy to stick with it!

You can check out my application at https://pointingparty.com/ and the source code on github.com/martijn/PointingParty.