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 { OrderIdad8= \"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 IClient56cFactory{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<ad0;OrderStatusResult>(new { OrderId = id});
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