使用Spring Cloud Stream和RabbitMQ实现事件驱动的微服务

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=<b>true</b>
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=<b>true</b>
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 <font>"streamInput.cities"</font><font> 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=<b>true</b> 

# 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=<b>true</b>
spring.cloud.stream.rabbit.bindings.personsChannel.consumer.bindingRoutingKey=persons
</font>

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。

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

<b>package</b> com.example.spring.cloud.configuration;

<b>import</b> org.springframework.cloud.stream.annotation.Input;
<b>import</b> org.springframework.messaging.SubscribableChannel;

<font><i>/**
 * Created by tomask79 on 30.03.17.
 */</i></font><font>
<b>public</b> <b>interface</b> SinkRabbitAPI {

    String INPUT_CITIES = </font><font>"citiesChannel"</font><font>;

    String INPUT_PERSONS = </font><font>"personsChannel"</font><font>;

    @Input(SinkRabbitAPI.INPUT_CITIES)
    SubscribableChannel citiesChannel();

    @Input(SinkRabbitAPI.INPUT_PERSONS)
    SubscribableChannel personsChannel();
}
</font>

Spring Boot启动时加载这个属性

<b>package</b> com.example.spring.cloud;

<b>import</b> com.example.spring.cloud.configuration.SinkRabbitAPI;
<b>import</b> com.example.spring.cloud.configuration.SourceRabbitAPI;
<b>import</b> org.springframework.boot.SpringApplication;
<b>import</b> org.springframework.boot.autoconfigure.SpringBootApplication;
<b>import</b> org.springframework.cloud.stream.annotation.EnableBinding;
<b>import</b> org.springframework.scheduling.annotation.EnableScheduling;

@SpringBootApplication
@EnableBinding({SinkRabbitAPI.<b>class</b>})
<b>public</b> <b>class</b> StreamingApplication {

    <b>public</b> <b>static</b> <b>void</b> main(String[] args) {
        SpringApplication.run(StreamingApplication.<b>class</b>, 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:

<b>import</b> com.example.spring.cloud.configuration.SinkRabbitAPI;
<b>import</b> com.example.spring.cloud.configuration.SourceRabbitAPI;
<b>import</b> org.springframework.cloud.stream.annotation.StreamListener;
<b>import</b> org.springframework.integration.support.MessageBuilder;
<b>import</b> org.springframework.messaging.MessageChannel;
<b>import</b> org.springframework.messaging.handler.annotation.SendTo;
<b>import</b> org.springframework.stereotype.Service;

<b>import</b> javax.annotation.Resource;

<font><i>/**
 * Created by tomask79 on 30.03.17.
 */</i></font><font>
@Service
<b>public</b> <b>class</b> ProcessingAMPQEndpoint {

    @StreamListener(SinkRabbitAPI.INPUT_CITIES)
    <b>public</b> <b>void</b> processCity(<b>final</b> String city) {
        System.out.println(</font><font>"Trying to process input city: "</font><font>+city);
    }

    @StreamListener(SinkRabbitAPI.INPUT_PERSONS)
    <b>public</b> <b>void</b> processPersons(<b>final</b> String person) {
        System.out.println(</font><font>"Trying to process input person: "</font><font>+person);
    }
}
</font>

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
  • git clone  https://tomask79@bitbucket.org/tomask79/spring-cloud-stream-rabbitmq.git
  • 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 <b>for</b> 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)
    <b>public</b> <b>void</b> processPersons(<b>final</b> String person) {
        System.out.println(<font>"Trying to process input person: "</font><font>+person);
        <b>throw</b> <b>new</b> RuntimeException();
    }
</font>

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。

原文 

https://www.jdon.com/51397

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