05 - Event-Driven Architecture Blueprint

Kiến trúc xây trên nền tảng sự kiện (events) thay vì gọi trực tiếp. Blueprint này dùng stack: .NET 9 + Next.js + Azure Service Bus + Azure Functions + SQL Server + Azure Entra ID (SSO).

Tổng Quan

Event Flow Chi Tiết

Khi Nào Dùng / Không Dùng

Dự án hay dùng: eCommerce (đặt hàng → xử lý kho → gửi mail), IoT telemetry, Logistics tracking, Fintech (fraud detection pipeline).

Project Structure (Full Stack)

eventdriven-app/
├── frontend/
│   └── next-app/
│       ├── app/
│       │   ├── layout.tsx
│       │   ├── page.tsx
│       │   ├── orders/
│       │   │   └── page.tsx
│       │   └── api/
│       │       └── auth/[...nextauth]/route.ts
│       ├── lib/
│       │   ├── auth.ts            ← MSAL.js config (Azure Entra ID)
│       │   └── api-client.ts      ← Fetch wrapper with Bearer Token
│       ├── next.config.js
│       └── package.json
│
├── backend/
│   ├── src/
│   │   ├── OrderApi/              ← .NET 9 Minimal API
│   │   │   ├── Program.cs
│   │   │   ├── Features/
│   │   │   │   ├── Orders/
│   │   │   │   │   ├── CreateOrder.cs
│   │   │   │   │   └── GetOrders.cs
│   │   │   │   └── Products/
│   │   │   ├── Infrastructure/
│   │   │   │   ├── AppDbContext.cs
│   │   │   │   ├── Outbox/
│   │   │   │   │   ├── OutboxMessage.cs
│   │   │   │   │   └── OutboxProcessor.cs   ← Background Service
│   │   │   │   └── Auth/
│   │   │   │       └── EntraIdExtensions.cs
│   │   │   ├── Dockerfile
│   │   │   └── appsettings.json
│   │   │
│   │   └── Functions/             ← Azure Functions (Isolated Worker)
│   │       ├── InventoryProcessor.cs
│   │       ├── EmailNotifier.cs
│   │       ├── AnalyticsIngestion.cs
│   │       ├── Program.cs
│   │       └── host.json
│   │
│   └── shared/
│       └── Contracts/
│           ├── Events/
│           │   ├── OrderCreatedEvent.cs
│           │   └── OrderCancelledEvent.cs
│           └── DTOs/
│               └── OrderDto.cs
│
├── infra/
│   ├── bicep/
│   │   ├── main.bicep
│   │   ├── servicebus.bicep
│   │   └── function.bicep
│   └── docker-compose.yml
│
└── eventdriven-app.sln

NuGet & NPM Checklist

Backend (.NET 9)

xml
<!-- Order API -->
<PackageReference Include="Microsoft.Identity.Web" Version="3.*" />  <!-- Entra ID -->
<PackageReference Include="MassTransit.Azure.ServiceBus.Core" Version="8.*" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.*" />
<PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="9.*" />
<PackageReference Include="Serilog.AspNetCore" Version="8.*" />

<!-- Azure Functions (Isolated) -->
<PackageReference Include="Microsoft.Azure.Functions.Worker" Version="2.*" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.ServiceBus" Version="5.*" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="2.*" />

Frontend (Next.js)

json
{
  "dependencies": {
    "next": "14.*",
    "@azure/msal-browser": "^3.0",
    "@azure/msal-react": "^2.0",
    "next-auth": "^5.0"
  }
}

Code Blueprint - Key Components

1. Azure Entra ID Setup (.NET API)

csharp
// Program.cs
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));

// appsettings.json
{
  "AzureAd": {
    "Instance": "https://login.microsoftonline.com/",
    "TenantId": "your-tenant-id",
    "ClientId": "your-api-client-id",
    "Audience": "api://your-api-client-id"
  }
}

2. Next.js MSAL Integration

typescript
// lib/auth.ts
import { PublicClientApplication } from "@azure/msal-browser";

export const msalConfig = {
  auth: {
    clientId: process.env.NEXT_PUBLIC_AZURE_CLIENT_ID!,
    authority: `https://login.microsoftonline.com/${process.env.NEXT_PUBLIC_AZURE_TENANT_ID}`,
    redirectUri: "http://localhost:3000",
  },
};

export const loginRequest = {
  scopes: ["api://your-api-client-id/.default"],
};

// lib/api-client.ts
export async function fetchWithAuth(url: string, msalInstance: PublicClientApplication) {
  const account = msalInstance.getActiveAccount();
  const token = await msalInstance.acquireTokenSilent({
    ...loginRequest,
    account: account!,
  });

  return fetch(url, {
    headers: { Authorization: `Bearer ${token.accessToken}` },
  });
}

3. Outbox Pattern (Reliable Event Publishing)

csharp
// Features/Orders/CreateOrder.cs
app.MapPost("/api/orders", async (CreateOrderRequest req, AppDbContext db) =>
{
    await using var tx = await db.Database.BeginTransactionAsync();

    var order = new Order { /* ... */ };
    db.Orders.Add(order);

    // Save event to Outbox (SAME transaction!)
    db.OutboxMessages.Add(new OutboxMessage
    {
        Id = Guid.NewGuid(),
        Type = nameof(OrderCreatedEvent),
        Payload = JsonSerializer.Serialize(new OrderCreatedEvent(order.Id, order.ProductId, order.Quantity)),
        CreatedAt = DateTime.UtcNow
    });

    await db.SaveChangesAsync();
    await tx.CommitAsync();

    return Results.Accepted($"/api/orders/{order.Id}");
});

4. Azure Function Consumer

csharp
// Functions/InventoryProcessor.cs
public class InventoryProcessor(IDbContextFactory<AppDbContext> dbFactory)
{
    [Function(nameof(ProcessOrderCreated))]
    public async Task ProcessOrderCreated(
        [ServiceBusTrigger("order-events", "inventory-processor",
            Connection = "ServiceBusConnection")]
        OrderCreatedEvent evt,
        FunctionContext context)
    {
        await using var db = await dbFactory.CreateDbContextAsync();

        var product = await db.Products.FindAsync(evt.ProductId);
        if (product is null || product.Stock < evt.Quantity)
        {
            // Publish compensation event
            throw new InvalidOperationException("Insufficient stock - will retry/DLQ");
        }

        product.Stock -= evt.Quantity;
        await db.SaveChangesAsync();
    }
}

5. Azure Service Bus Topic/Subscription

Infrastructure as Code (Bicep)

bicep
// infra/bicep/servicebus.bicep
resource serviceBusNamespace 'Microsoft.ServiceBus/namespaces@2022-10-01-preview' = {
  name: 'myapp-sb-${environment}'
  location: location
  sku: { name: 'Standard', tier: 'Standard' }
}

resource topic 'Microsoft.ServiceBus/namespaces/topics@2022-10-01-preview' = {
  parent: serviceBusNamespace
  name: 'order-events'
  properties: { maxSizeInMegabytes: 1024 }
}

resource inventorySub 'Microsoft.ServiceBus/namespaces/topics/subscriptions@2022-10-01-preview' = {
  parent: topic
  name: 'inventory-processor'
  properties: {
    maxDeliveryCount: 3
    deadLetteringOnMessageExpiration: true
  }
}