Injecting tenant information in a SignalR Hub's OnConnected/OnDisconnected

Question

There is a multi-tenant SaaS app where I want to create groups for each tenantIds in the SignalR Hub's OnConnectedAsync/OnDisconnectedAsync hook.

The problem is that ITenancyContext<ApplicationTenant> is registered as a scoped service, which means it is only available within the scope of a request. In the context of a SignalR hub, it is not associated with a request, and thus it is not available.

So how do I make it available? Authorize it and enrich the claims somehow?

public sealed class NotificationHub : Hub
{
    readonly ILogger<NotificationHub> _logger;
    readonly Guid _tenantId;

    public NotificationHub(ILogger<NotificationHub> logger, ITenancyContext<ApplicationTenant> tenancyContext) => (_logger, _tenantId) = (logger, tenancyContext.Tenant.Id);

    public override async Task OnConnectedAsync()
    {
        await JoinGroup(_tenantId.ToString());
        _logger.LogInformation("{ConnectionId} has connected to the hub. TenantId: {TenantId}", Context.ConnectionId, _tenantId);
        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        await LeaveGroup(_tenantId.ToString());
        _logger.LogInformation("{ConnectionId} was disconnected from the hub. TenantId: {TenantId}", Context.ConnectionId, _tenantId);
        await base.OnDisconnectedAsync(exception);
    }

    Task JoinGroup(string groupName) => Groups.AddToGroupAsync(Context.ConnectionId, groupName);

    Task LeaveGroup(string groupName) => Groups.RemoveFromGroupAsync(Context.ConnectionId, groupName);
}

Answer 1

I think we can create a middleware to implement it. Inject ITenancyContext<ApplicationTenant> in this middlerware, let call it TenantMiddleware.

public class TenantMiddleware
{
    private readonly ITenancyContext<ApplicationTenant> _tenancyContext;

    public TenantMiddleware(ITenancyContext<ApplicationTenant> tenancyContext)
    {
        _tenancyContext = tenancyContext;
    }

    public async Task InvokeAsync(HttpContext context, Func<Task> next)
    {
        var user = context.User.Identity as ClaimsIdentity;
        if (user != null)
        {
            var TenantId= _tenancyContext.Tenant.Id;
            user.AddClaim(new Claim("TenantId", TenantId.ToString()));
        }

        await next();
    }
}

Then we can use it in your NotificationHub class.

public override async Task OnConnectedAsync()
{
    // Get TenantId like below.
    var user = Context.User.Identity as ClaimsIdentity;
    var tenantIdClaim = user?.FindFirst("TenantId");
    _tenantId = tenantIdClaim != null ? Guid.Parse(tenantIdClaim.Value) : Guid.Empty;
    ...
    await JoinGroup(_tenantId.ToString());
    _logger.LogInformation("{ConnectionId} has connected to the hub. TenantId: {TenantId}", Context.ConnectionId, _tenantId);
    await base.OnConnectedAsync();
}