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Autofac.AspNetCore.Multitenant

ASP.NET Core support for multitenant DI via Autofac.Multitenant.

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Please file issues and pull requests for this package in this repository rather than in the Autofac core repo.

Why Use This?

ASP.NET Core default RequestServicesContainerMiddleware is where the per-request lifetime scope usually gets generated. However, its constructor is where it wants the IServiceScopeFactory that will be used later during the request to create the request lifetime scope.

Unfortunately, that means the IServiceScopeFactory is created/resolved at the point when the request comes in, long before an HttpContext is set in any IHttpContextAccessor. The result is the scope factory ends up coming from the default tenant scope, before a tenant can be identified, and per-request services will later all come from the default tenant. Multitenancy fails.

This package provides a different request services middleware that ensures the IHttpContextAccessor.HttpContext is set and defers creation of the request lifetime scope until as late as possible so anything needed for tenant identification can be established.

Quick Start

When creating your application host, use the multitenant service provider factory. Your Startup will register common dependencies, but you'll need to provide a static method to initialize the tenant-specific overrides.

var host = Host.CreateDefaultBuilder(args)
    .UseServiceProviderFactory(new AutofacMultitenantServiceProviderFactory(MultitenantContainerSetup.ConfigureMultitenantContainer))
    .ConfigureWebHostDefaults(webHostBuilder => webHostBuilder.UseStartup<Startup>())
    .Build();

In your Startup class, make sure to use the multitenant request services middleware and register your common dependencies.

public class Startup
{
  public void ConfigureServices(IServiceCollection services)
  {
    // Add the multitenant request services handler.
    services
      .AddAutofacMultitenantRequestServices()
      .AddControllers();
  }

  public void ConfigureContainer(ContainerBuilder builder)
  {
    // Register tenant-shared dependencies and defaults.
    builder.RegisterType<CommonDependency>()
      .As<IDependency>()
      .InstancePerLifetimeScope();
  }

  public void Configure(IApplicationBuilder app)
  {
      app.UseRouting();
      app.UseEndpoints(builder => builder.MapControllers());
  }
}

Provide a method to override things for tenant-specific dependencies. This is what gets passed to the multitenant service provider factory.

public static class MultitenantContainerSetup
{
  public static MultitenantContainer ConfigureMultitenantContainer(IContainer container)
  {
    // Define how you're going to identify tenants.
    var strategy = new QueryStringTenantIdentificationStrategy(
        container.Resolve<IHttpContextAccessor>(),
        container.Resolve<ILogger<QueryStringTenantIdentificationStrategy>>());

    // Create the multitenant container.
    var multitenantContainer = new MultitenantContainer(strategy, container);

    // Register tenant overrides.
    multitenantContainer.ConfigureTenant(
        "some-tenant",
        cb => cb
          .RegisterType<OverrideDependency>()
          .As<IDependency>()
          .WithProperty("Id", "some-tenant")
          .InstancePerLifetimeScope());

    // Return the built container for use in the app.
    return multitenantContainer;
  }
}

Reference