How to access a request scoped service when generating a resolver scoped DbContext (Multi-tenancy, multi database)

[kpschaper]

Hi,

I'm trying to implement multi-tenancy (Database per tenant) using Hotchocolate and Entity Framework Core based on the following blogpost:
https://youssefsellami.com/implementing-multi-tenancy-with-entityframework-core/

Instead of having as separate TenantMiddleware, I get the TenantId from the HttpRequest by overriding the OnCreateAsync method in the DefaultHttpRequestInterceptor.

In the Program.cs only the TenantDbContext is registered with DbContext.Resolver (default), this creates a problem as with DbContext.Resolver a new resolver scope is created for the DbContext.
Therefore the ITenantProvider with request scope is not accessable anymore when adding a new TenantDbContext.

How do I fix this?

HttpRequestInterceptor.cs

public override async ValueTask OnCreateAsync(HttpContext context, IRequestExecutor requestExecutor, IQueryRequestBuilder requestBuilder, CancellationToken cancellationToken)
{
    await base.OnCreateAsync(context, requestExecutor, requestBuilder, cancellationToken);

    var dbContext = context.RequestServices.GetService<CentralDbContext>();
    var tenantProvider = context.RequestServices.GetService<ITenantProvider>();

    if (context.Request.Headers.TryGetValue("TenantId", out var headerValue) && int.TryParse(headerValue.ToString(), out var tenantId))
    {
        var tenant = await dbContext.Tenants.FirstOrDefaultAsync(e => e.Id == tenantId);
        if (tenant != null)
        {
            tenantProvider.SetTenant(tenant);
            return;
        }
    }
}

Program.cs

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddScoped<ITenantProvider, TenantProvider>();

// register the db contexts
builder.Services.AddDbContext<CentralDbContext>(options =>
{
    options.UseMySql(_connectionString, ServerVersion.AutoDetect(connectionString));
});

builder.Services.AddDbContext<TenantDbContext>((serviceProvider, options) =>
{
    var tenantProvider = serviceProvider.GetService<ITenantProvider>();
    var tenant = tenantProvider?.GetTenant();
    if (tenant is null)
        throw new TenantNotSetException();

    // set the db context to the tenant connection string
    options.UseMySql(tenant.ConnectionString, ServerVersion.AutoDetect(tenant.ConnectionString));
});

builder.Services
    .AddGraphQLServer()
    .AddHttpRequestInterceptor<HttpRequestInterceptor>()
    .AddTypes()
    .RegisterDbContext<TenantDbContext>();

var app = builder.Build();

app.UseStaticFiles();
app.UseRouting();
app.MapGraphQL();

app.Run();