.NET 雲原生架構師訓練營(模組二 基礎鞏固 RabbitMQ Masstransit 詳解)--學習筆記
2021-01-13 23:00:19 軟體

2.6.7 RabbitMQ -- Masstransit 詳解

  • Consumer 消費者
  • Producer 生產者
  • Request-Response 請求-響應

Consumer 消費者

在 MassTransit 中,一個消費者可以消費一種或多種訊息

消費者的型別包括:普通消費者,saga,saga 狀態機,路由活動(分散式追蹤),處理器 handlers,工作消費者 job comsumers

  • Consumer
  • Instance
  • Handler
  • Others

Consumer

public class Program
{
    public static async Task Main()
    {
        var busControl = Bus.Factory.CreateUsingRabbitMq(cfg =>
        {
            cfg.ReceiveEndpoint("order-service", e =>
            {
                e.Consumer<SubmitOrderConsumer>();
            });
        });
    }
}

繼承 IConsumer,實現 Consume 方法

class SubmitOrderConsumer :
    IConsumer<SubmitOrder>
{
    public async Task Consume(ConsumeContext<SubmitOrder> context)
    {
        await context.Publish<OrderSubmitted>(new
        {
            context.Message.OrderId
        });
    }
}

三個原則:

  • 擁抱 The Hollywood Principle, which states, "Dont't call us, we'll call you."
  • Consume 方法是一個被等待的方法,在執行中時其他消費者無法接收到這個訊息,當這個方法完成的時候,訊息被 ack,並且從佇列中移除
  • Task 方法異常會導致訊息觸發 retry,如果沒有設定重試,訊息將被投遞到失敗佇列

Instance

public class Program
{
    public static async Task Main()
    {
        var submitOrderConsumer = new SubmitOrderConsumer();

        var busControl = Bus.Factory.CreateUsingRabbitMq(cfg =>
        {
            cfg.ReceiveEndpoint("order-service", e =>
            {
                e.Instance(submitOrderConsumer);
            });
        });
    }
}

所有接收到的訊息都由一個消費者來範例來處理(請確保這個消費者類是執行緒安全)

Consumer 每次接收到訊息都會 new 一個範例

Handler

public class Program
{
    public static async Task Main()
    {
        var busControl = Bus.Factory.CreateUsingRabbitMq(cfg =>
        {
            cfg.ReceiveEndpoint("order-service", e =>
            {
                e.Handler<SubmitOrder>(async context =>
                {
                    await Console.Out.WriteLineAsync($"Submit Order Received: {context.Message.OrderId}");
                });
            });
        });
    }
}

通過一個委託 Lambda 方法,來消費訊息

Others

  • Saga<>
  • StateMachineSaga<>

Producer 生產者

訊息的生產可以通過兩種方式產生:傳送和釋出

傳送的時候需要指定一個具體的地址 DestinationAddress,釋出的時候訊息會被廣播給所有訂閱了這個訊息型別的消費者

基於這兩種規則,訊息被定義為:命令 command 和事件 event

  • send
  • publish

send

可以呼叫以下物件的 send 方法來傳送 command:

  • ConsumeContext (在 Consumer 的 Consumer 方法引數中傳遞)
  • ISendEndpointProvider(可以從 DI 中獲取)
  • IBusControl(最頂層的控制物件,用來啟動和停止 masstransit 的控制器)

ConsumeContext

public class SubmitOrderConsumer : 
    IConsumer<SubmitOrder>
{
    private readonly IOrderSubmitter _orderSubmitter;

    public SubmitOrderConsumer(IOrderSubmitter submitter)
        => _orderSubmitter = submitter;

    public async Task Consume(IConsumeContext<SubmitOrder> context)
    {
        await _orderSubmitter.Process(context.Message);

        await context.Send(new StartDelivery(context.Message.OrderId, DateTime.UtcNow));
    }
}

ISendEndpointProvider

public async Task SendOrder(ISendEndpointProvider sendEndpointProvider)
{
    var endpoint = await sendEndpointProvider.GetSendEndpoint(_serviceAddress);

    await endpoint.Send(new SubmitOrder { OrderId = "123" });
}

publish

  • 傳送地址
  • 短地址
  • Convention Map

傳送地址

  • rabbitmq://localhost/input-queue
  • rabbitmq://localhost/input-queue?durable=false

短地址

  • GetSendEndpoint(new Uri("queue:input-queue"))

Convention Map

在組態檔中指定 map 規則

EndpointConvention.Map<StartDelivery>(new Uri(ConfigurationManager.AppSettings["deliveryServiceQueue"]));

直接傳送

public class SubmitOrderConsumer : 
    IConsumer<SubmitOrder>
{
    private readonly IOrderSubmitter _orderSubmitter;

    public SubmitOrderConsumer(IOrderSubmitter submitter)
        => _orderSubmitter = submitter;

    public async Task Consume(IConsumeContext<SubmitOrder> context)
    {
        await _orderSubmitter.Process(context.Message);

        await context.Send(new StartDelivery(context.Message.OrderId, DateTime.UtcNow));
    }
}

可以呼叫以下物件的 publish 方法來傳送 event:

  • ConsumeContext (在 Consumer 的 Consumer 方法引數中傳遞)
  • IPublishEndpoint(可以從 DI 中獲取)
  • IBusControl(最頂層的控制物件,用來啟動和停止 masstransit 的控制器)

IPublishEndpoint

public async Task NotifyOrderSubmitted(IPublishEndpoint publishEndpoint)
{
    await publishEndpoint.Publish<OrderSubmitted>(new
    {
        OrderId = "27",
        OrderDate = DateTime.UtcNow,
    });
}

Request-Response 請求-響應

Request-Response 模式讓應用程式之間解耦之後,依然採用同步的方式

  • Consumer
  • IClientFactory
  • IRequestClient
  • Send a request

Consumer

public async Task Consume(ConsumeContext<CheckOrderStatus> context)
{
    var order = await _orderRepository.Get(context.Message.OrderId);
    if (order == null)
        throw new InvalidOperationException("Order not found");
    
    await context.RespondAsync<OrderStatusResult>(new 
    {
        OrderId = order.Id,
        order.Timestamp,
        order.StatusCode,
        order.StatusText
    });
}

需要處理返回型別 OrderStatusResult,非同步方式模擬同步,實際上同樣有訊息佇列,消費者處理過程

IClientFactory

public interface IClientFactory 
{
    IRequestClient<T> CreateRequestClient<T>(ConsumeContext context, Uri destinationAddress, RequestTimeout timeout);

    IRequestClient<T> CreateRequestClient<T>(Uri destinationAddress, RequestTimeout timeout);

    RequestHandle<T> CreateRequest<T>(T request, Uri destinationAddress, CancellationToken cancellationToken, RequestTimeout timeout);

    RequestHandle<T> CreateRequest<T>(ConsumeContext context, T request, Uri destinationAddress, CancellationToken cancellationToken, RequestTimeout timeout);
}

通過 IBusControl 的 CreateClientFactory 方法可以得到 ClientFactory

IRequestClient

public interface IRequestClient<TRequest>
    where TRequest : class
{
    RequestHandle<TRequest> Create(TRequest request, CancellationToken cancellationToken, RequestTimeout timeout);

    Task<Response<T>> GetResponse<T>(TRequest request, CancellationToken cancellationToken, RequestTimeout timeout);
}

RequestClient 可以建立請求,或者直接獲得響應

Send a request

var serviceAddress = new Uri("rabbitmq://localhost/check-order-status");
var client = bus.CreateRequestClient<CheckOrderStatus>(serviceAddress);

var response = await client.GetResponse<OrderStatusResult>(new { OrderId = id});

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