SignalR healthcheck issue

[ChrisProlls]

Please, fill the following sections to help us fix the issue

What happened: I tried to use the SignalR healthcheck but I faced with a Object reference not set to an instance of an object. into the health check portal.

What you expected to happen: I expect the health check to work properly

Source code sample: I used this code :

services.AddHealthChecks()
                .AddSignalRHub("/Hub", name: "signalr hub")
                .AddSignalRHub("/UploaderHub", name: "signalr uploader")
                .AddHealthChecksUI(setup =>
                {
                    setup.AddHealthCheckEndpoint("HealthCheck", "/healthz");
                    setup.SetEvaluationTimeInSeconds(60);
                })
                .AddInMemoryStorage();

and for my route configuration

app
                .UseHealthChecks("/healthz", new HealthCheckOptions
                {
                    Predicate = _ => true,
                    ResponseWriter = UIResponseWriter.WriteHealthCheckUIResponse
                })
                .UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapHub<UploaderHub>("/UploaderHub");
                endpoints.MapHub<ClientHub>("/Hub");
                endpoints.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
                endpoints.MapRazorPages();
                endpoints.MapHealthChecksUI(options => options.UIPath = "/health-ui");
            });

Into the health check, I assume that this line returns null, but can't figure out why:

new HubConnectionBuilder()
                    .WithUrl(url)
                    .Build();

Anything else we need to know?: Ths UI portal is showing correctly, others health check (sql, redis) are working properly.

Environment:

• .NET Core version : 3.1.100
• Healthchecks version : 3.1.1
• Operative system: Windows

[unaizorrilla]

Hi @ChrisProlls

Thanks for submitting the issue!

Well, the issue is related with your Uri configuration for the SignalR hubs. AddSignalRHub need the hub uri, not the path string, ie /hub.

When the healthcheck perform the iteration, the HubConnectionBuilder throw because this uri is not valid.

Can you set the valid Uri for the Hub and test if this works well?

Please, close the issue if this solve the problem!

[ChrisProlls]

So, if I understand correctly, I need the full SignalR hub URL into my Startup ? For example : https://mydomain.com/hub ?

Into the startup it's not possible to retrive the domain name, so I would have to store it into the configuration files.

[unaizorrilla]

@ChrisProlls

Yeap, you need to set the uri in configuration vars! Is not easy to get the domain name at startup time