【本人秃顶程序员】使用Spring Cloud Stream和RabbitMQ实现事件驱动的微服务

小咪咪 2022-04-23 08:26 190阅读 0赞

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让我们展示如何使用Spring Cloud Stream来设计事件驱动的微服务。首先，Spring Cloud Stream首先有什么好处？因为Spring AMPQ提供了访问AMPQ工件所需的一切。如果您不熟悉Spring AMPQ，请查看此repo，其中包含许多有用的示例。那么为什么要使用Spring Cloud Stream …？

### Spring Cloud Stream概念 ###

*  Spring Cloud Stream通过Binder概念将使用过的消息代理与Spring Integration消息通道绑定在一起。支持RabbitMQ和Kafka。
 *  Spring Cloud Stream将基础架构配置从代码中分离为属性文件。这意味着即使您更改了底层代理，您的Spring Integration代码也将是相同的！

### 示例中的Spring Cloud Stream概念（RabbitMQ） ###

让我们有一个名为streamInput的交换，它有两个队列streamInput.cities和streamInput.persons。现在让我们将这两个队列插入两个消息通道citiesChannel和personsChannel来消费来自它的传入消息。使用Spring AMPQ，您需要创建SimpleMessageListenerContainer并在代码中连接基础结构。但这有很多样板代码。使用Spring Cloud Stream，您可以将AMPQ配置分离到属性文件：

spring.cloud.stream.bindings.citiesChannel.destination=streamInput
    spring.cloud.stream.bindings.citiesChannel.group=cities
    spring.cloud.stream.rabbit.bindings.citiesChannel.consumer.durableSubscription=true
    spring.cloud.stream.rabbit.bindings.citiesChannel.consumer.bindingRoutingKey=cities
    
    spring.cloud.stream.bindings.personsChannel.destination=streamInput
    spring.cloud.stream.bindings.personsChannel.group=persons
    spring.cloud.stream.rabbit.bindings.personsChannel.consumer.durableSubscription=true
    spring.cloud.stream.rabbit.bindings.personsChannel.consumer.bindingRoutingKey=persons

### 配置详细信息 ###

在类路径上使用RabbitMQ Binder,每个目标都映射到TopicExchange。在示例中，我创建了名为streamInput的TopicExchange， 并将其附加到两个消息通道citiesChannel和personsChannel。

spring.cloud.stream.bindings.citiesChannel.destination = streamInput 
    spring.cloud.stream.bindings.personsChannel.destination = streamInput

现在您需要了解RabbitMQ绑定器的灵感来自Kafka，队列的消费者被分组到消费者组中，其中只有一个消费者将获得消息。这是有道理的，因为您可以轻松扩展消费者。

因此，让我们创建两个队列streamInput.persons和streamInput.cities并将它们附加到streamInput TopicExchange和提到的消息通道

# This will create queue "streamInput.cities" connected to message channel citiesChannel where input messages will land.
    spring.cloud.stream.bindings.citiesChannel.group=cities 
    
    # Durable subscription, of course.
    spring.cloud.stream.rabbit.bindings.citiesChannel.consumer.durableSubscription=true 
    
    # AMPQ binding to exchange (previous spring.cloud.stream.bindings.<channel name>.destination settings).
    # Only messages with routingKey = 'cities' will land here.
    spring.cloud.stream.rabbit.bindings.citiesChannel.consumer.bindingRoutingKey=cities 
    
    spring.cloud.stream.bindings.personsChannel.group=persons
    spring.cloud.stream.rabbit.bindings.personsChannel.consumer.durableSubscription=true
    spring.cloud.stream.rabbit.bindings.personsChannel.consumer.bindingRoutingKey=persons

### 连接属性到Spring Integration ###

好的，到目前为止我创建了两个队列。StreamInput.cities绑定到citiesChannel。StreamInput.persons绑定到peopleChannel。

.是Spring Cloud Stream约定的队列命名，现在让我们将它连接到Spring Integration：

package com.example.spring.cloud.configuration;
    
    import org.springframework.cloud.stream.annotation.Input;
    import org.springframework.messaging.SubscribableChannel;
    
    /**
     * Created by tomask79 on 30.03.17.
     */
    public interface SinkRabbitAPI {
    
        String INPUT_CITIES = "citiesChannel";
    
        String INPUT_PERSONS = "personsChannel";
    
        @Input(SinkRabbitAPI.INPUT_CITIES)
        SubscribableChannel citiesChannel();
    
        @Input(SinkRabbitAPI.INPUT_PERSONS)
        SubscribableChannel personsChannel();
    }

Spring Boot启动时加载这个属性

package com.example.spring.cloud;
    
    import com.example.spring.cloud.configuration.SinkRabbitAPI;
    import com.example.spring.cloud.configuration.SourceRabbitAPI;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.stream.annotation.EnableBinding;
    import org.springframework.scheduling.annotation.EnableScheduling;
    
    @SpringBootApplication
    @EnableBinding({SinkRabbitAPI.class})
    public class StreamingApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(StreamingApplication.class, args);
        }
    }

在此之后，我们可以创建消费者从绑定的消息通道中的队列接收消息：

import com.example.spring.cloud.configuration.SinkRabbitAPI;
    import com.example.spring.cloud.configuration.SourceRabbitAPI;
    import org.springframework.cloud.stream.annotation.StreamListener;
    import org.springframework.integration.support.MessageBuilder;
    import org.springframework.messaging.MessageChannel;
    import org.springframework.messaging.handler.annotation.SendTo;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    
    /**
     * Created by tomask79 on 30.03.17.
     */
    @Service
    public class ProcessingAMPQEndpoint {
    
        @StreamListener(SinkRabbitAPI.INPUT_CITIES)
        public void processCity(final String city) {
            System.out.println("Trying to process input city: "+city);
        }
    
        @StreamListener(SinkRabbitAPI.INPUT_PERSONS)
        public void processPersons(final String person) {
            System.out.println("Trying to process input person: "+person);
        }
    }

RabbitMQ绑定器和代理配置

Spring Cloud Stream如何知道在哪里寻找消息中间件？如果在类路径中找到RabbitMQ绑定器，则使用默认RabbitMQ主机（localhost）和端口（5672）连接到RabbitMQ服务器。如果您的消息中间件配置在不同端口，则需要配置属性：

spring:
      cloud:
        stream:
          bindings:
            ...
          binders:
              rabbitbinder:
                type: rabbit
                environment:
                  spring:
                    rabbitmq:
                      host: rabbitmq
                      port: 5672
                      username: XXX
                      password: XXX

测试消息消费

*  安装并运行RabbitMQ代理
 *  mvn clean install
 *  java -jar target / streaming-0.0.1-SNAPSHOT.jar
 *  现在使用路由键’cities’或’persons’在streamInput Exchange上发布消息…输出应该是：

Started StreamingApplication in 6.513 seconds (JVM running for 6.92) 
    Trying to process input city: sdjfjljksdflkjsdflkjsdfsfd
    Trying to process input person: sdjfjljksdflkjsdflkjsdfsfd

### 使用Spring Cloud Stream重新传递消息 ###

您通常希望在进入DLX交换之前再次尝试接收消息。首先，让我们配置Spring Cloud Stream尝试重新发送失败消息的次数：

spring.cloud.stream.bindings.personsChannel.consumer.maxAttempts = 6

这意味着如果从streamInput.persons队列接收的消息出错，那么Spring Cloud Stream将尝试重新发送六次。让我们试试，首先让我们修改接收端点以模拟接收崩溃：

@StreamListener(SinkRabbitAPI.INPUT_PERSONS)
        public void processPersons(final String person) {
            System.out.println("Trying to process input person: "+person);
            throw new RuntimeException();
        }

如果我现在尝试使用人员路由键将某些内容发布到streamInput交换中，那么这应该是输出：

Trying to process input person: sfsdfsdfsd
    Trying to process input person: sfsdfsdfsd
    Trying to process input person: sfsdfsdfsd
    Trying to process input person: sfsdfsdfsd
    Trying to process input person: sfsdfsdfsd
    Trying to process input person: sfsdfsdfsd
     Retry Policy Exhausted
            at org.springframework.amqp.rabbit.retry.RejectAndDontRequeueRecoverer.recover
    (RejectAndDontRequeueRecoverer.java:45) ~[spring-rabbit-1.7.0.RELEASE.jar! /:na]
            at org.springframework.amqp.rabbit.config.StatelessRetryOperationsInterc

建议将Spring Cloud Stream 用于事件驱动的MicroServices，因为它可以节省时间，而且您不需要为Java中的AMPQ基础架构编写样板代码。

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