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.NET 云原生架构师训练营(模块二 基础巩固 RabbitMQ Masstransit 详解)--学习笔记

2.6.7 RabbitMQ -- Masstransit 详解

  • Consumer 消费者
  • Producer 生产者
  • Request-Response 请求-响应

Consumer 消费者

在 MassTransit 中,一个消费者可以消费一种或多种消息

消费者的类型包括:普通消费者,saga,saga 状态机,路由活动(分布式追踪),处理器 handlers,工作消费者 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>();
            });
        });
    }
}

继承 IConsumer,实现 Consume 方法

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

三个原则:

  • 拥抱 The Hollywood Principle, which states, "Dont't call us, we'll call you."
  • Consume 方法是一个被等待的方法,在执行中时其他消费者无法接收到这个消息,当这个方法完成的时候,消息被 ack,并且从队列中移除
  • Task 方法异常会导致消息触发 retry,如果没有配置重试,消息将被投递到失败队列

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);
            });
        });
    }
}

所有接收到的消息都由一个消费者来实例来处理(请确保这个消费者类是线程安全)

Consumer 每次接收到消息都会 new 一个实例

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}");
                });
            });
        });
    }
}

通过一个委托 Lambda 方法,来消费消息

Others

  • Saga<>
  • StateMachineSaga<>

Producer 生产者

消息的生产可以通过两种方式产生:发送和发布

发送的时候需要指定一个具体的地址 DestinationAddress,发布的时候消息会被广播给所有订阅了这个消息类型的消费者

基于这两种规则,消息被定义为:命令 command 和事件 event

  • send
  • publish

send

可以调用以下对象的 send 方法来发送 command:

  • ConsumeContext (在 Consumer 的 Consumer 方法参数中传递)
  • ISendEndpointProvider(可以从 DI 中获取)
  • IBusControl(最顶层的控制对象,用来启动和停止 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

  • 发送地址
  • 短地址
  • Convention Map

发送地址

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

短地址

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

Convention Map

在配置文件中指定 map 规则

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

直接发送

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));
    }
}

可以调用以下对象的 publish 方法来发送 event:

  • ConsumeContext (在 Consumer 的 Consumer 方法参数中传递)
  • IPublishEndpoint(可以从 DI 中获取)
  • IBusControl(最顶层的控制对象,用来启动和停止 masstransit 的控制器)

IPublishEndpoint

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

Request-Response 请求-响应

Request-Response 模式让应用程序之间解耦之后,依然采用同步的方式

  • 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
    });
}

需要处理返回类型 OrderStatusResult,异步方式模拟同步,实际上同样有消息队列,消费者处理过程

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);
}

通过 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 可以创建请求,或者直接获得响应

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});

课程链接

https://appsqsyiqlk5791.h5.xiaoeknow.com/v1/course/video/v_5f39bdb8e4b01187873136cf?type=2

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posted @ 2021-01-13 22:52  郑子铭  阅读(654)  评论(0编辑  收藏  举报