Recommended lifecycle for services using SignalR hubs

Question

I'm injecting following service with the SignalR ContentHub in various controllers in a ASP.NET Core web application (running on .NET Core 2.2). Currently the service is injected with a transient lifecycle. Using singleton lifecycle would be better? Is the transient lifecycle in this case a possible source for performance issues?

public class PushMessageService : IPushMessageService
{
    private readonly ILogger<PushMessageService> _logger;
    private readonly IHubContext<ContentHub> _context;

    public PushMessageService(
        ILogger<PushMessageService> logger,
        IHubContext<ContentHub> context
    )
    {
        _logger = logger;
        _context = context;
    }    

    public async Task Push(int productId)
    {
        var msg = new Message
        {
            ProductId = productId
        };

        await SendAsync("PushMsg", productId, msg);
    }

    private async Task SendAsync<TPayload>(string methodName, int productId, TPayload payload)
    {
        await _context.Clients.Group("prod" + productId).SendAsync(methodName, payload);
    }
}

Answer 1

The IHubContext abstraction that wraps the hub is a singleton. As such, the lifetime of the class using it as a dependency doesn't really matter. Whether you use a singleton, scoped, or transient lifetime, you always get the same instance.