PouryaKit.Modularity 0.1.0-preview.1

PouryaKit.Modularity

Modules for a Host. A Module is a business boundary that declares what it needs and offers in one public class, its Composition Root, and keeps everything else internal. Anything outside it, an endpoint, a job, another Module or a test, runs one of its Operations through its Gateway and passes an Operation Context that says which Actor it runs for.

Install

dotnet add package PouryaKit.Modularity --prerelease

When to use it

• You are writing a Module's Composition Root, or composing the Host from its Modules.
• Code outside a Module needs to run one of its commands or queries.
• One Module needs an answer from another before its Operation can go on.
• A Host fails when it is built or started, and you want to know which check stopped it.

It builds on PouryaKit.Cqrs. A Host with a single Module may leave it out, as the monolith template does until a second Module arrives.

Quick start

Add each Module to the Host:

builder.AddPouryaKitModules(modules => modules.Add<InventoryModule>());

Declare the Module in its Composition Root, as the Proving Sample's Billing does:

public sealed class BillingModule : IModuleDefinition
{
    public void Configure(ModuleBuilder module)
    {
        module.UsePouryaKitPostgres<BillingDbContext>(connectionName: "app", schema: "billing");
        module.AddPouryaKitCqrs();
        module.Subscribe<ProductCreatedV1, OpenPriceListIntegrationEventHandler>(
            "billing.product-created"
        );
        module.Subscribe<AccountOpenedV1, OpenWelcomeQuoteIntegrationEventHandler>(
            "billing.account-opened"
        );
        module.AddPouryaKitDelayedCommand<ExpireQuoteCommand>("billing.expire-quote");
    }
}

Run an Operation through its Gateway, with the context of the running request. This endpoint also needs PouryaKit.Web, which begins the request's Operation and supplies ToHttpResult():

routes.MapGet(
    "/stock-items/{productId}",
    async (
        Guid productId,
        OperationContext context,
        IGatewayProcessor<InventoryModule> inventory,
        CancellationToken cancellationToken
    ) =>
        (
            await inventory.QueryAsync(
                new GetStockItemQuery(productId),
                context,
                cancellationToken
            )
        ).ToHttpResult()
);

What you get

• One public class per Module, with everything else internal, and architecture tests that hold the boundary.
• IGatewayProcessor<TModule>, the only way in: each call is one Operation in a scope of its own.
• Every Operation belongs to one Module, which owns what it declares.
• A Host that fails when it is built or started, naming what its composition got wrong, before it serves.

Learn more

• Modules
• Host and Module
• Add a Module
• The Host's checks