springcloud学习笔记(十二) 消息总线(Spring Cloud Bus)

电玩女神 2022-05-31 12:05 195阅读 0赞

Spring Cloud Bus 将分布式的节点用轻量的消息代理连接起来。它可以用于广播配置文件的更改或者服务之间的通讯，也可以用于监控。本文要讲述的是用Spring Cloud Bus实现通知微服务架构的配置文件的更改。

### 一、准备工作 ###

本文还是基于上一篇文章来实现。按照官方文档，我们只需要在配置文件中配置 spring-cloud-starter-bus-amqp ；这就是说我们需要装rabbitMq，点击[rabbitmq][]下载。至于怎么使用 rabbitmq，搜索引擎下。

### 二、改造config-client ###

在pom文件加上起步依赖spring-cloud-starter-bus-amqp，完整的配置文件如下：

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.forezp</groupId>
        <artifactId>config-client</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
    
        <name>config-client</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.2.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.retry</groupId>
                <artifactId>spring-retry</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-config</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-aop</artifactId>
            </dependency>
    
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-eureka</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-bus-amqp</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-actuator</artifactId>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Dalston.RC1</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>
    
    
    </project>

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在配置文件application.properties中加上RabbitMq的配置，包括RabbitMq的地址、端口，用户名、密码，代码如下：

spring.rabbitmq.host=localhost
    spring.rabbitmq.port=5672
    # spring.rabbitmq.username=
    # spring.rabbitmq.password=

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如果rabbitmq有用户名密码，输入即可。

依次启动eureka-server、confg-cserver,启动两个config-client，端口为：8881、8882。

访问[http://localhost:8881/hi][http_localhost_8881_hi] 或者[http://localhost:8882/hi][http_localhost_8882_hi] 浏览器显示：

> foo version 3

这时我们去[代码仓库][Link 1]将foo的值改为“foo version 4”，即改变配置文件foo的值。如果是传统的做法，需要重启服务，才能达到配置文件的更新。此时，我们只需要发送post请求：[http://localhost:8881/bus/refresh][http_localhost_8881_bus_refresh]，你会发现config-client会重新读取配置文件

![Paste\_Image.png][Paste_Image.png]

重新读取配置文件：

![Paste\_Image.png][Paste_Image.png 1]

这时我们再访问[http://localhost:8881/hi][http_localhost_8881_hi] 或者[http://localhost:8882/hi][http_localhost_8882_hi] 浏览器显示：

> foo version 4

另外，/bus/refresh接口可以指定服务，即使用”destination”参数，比如 “/bus/refresh?destination=customers:\*\*” 即刷新服务名为customers的所有服务，不管ip。

### 三、分析 ###

此时的架构图：   
![Paste\_Image.png][Paste_Image.png 2]

当git文件更改的时候，通过pc端用post 向端口为8882的config-client发送请求/bus/refresh／；此时8882端口会发送一个消息，由消息总线向其他服务传递，从而使整个微服务集群都达到更新配置文件。

### 四、其他扩展（可忽视） ###

可以用作自定义的Message Broker,只需要spring-cloud-starter-bus-amqp, 然后再配置文件写上配置即可，同上。

Tracing Bus Events：   
需要设置：spring.cloud.bus.trace.enabled=true，如果那样做的话，那么Spring Boot TraceRepository（如果存在）将显示每个服务实例发送的所有事件和所有的ack,比如：（来自官网）

{
      "timestamp": "2015-11-26T10:24:44.411+0000",
      "info": {
        "signal": "spring.cloud.bus.ack",
        "type": "RefreshRemoteApplicationEvent",
        "id": "c4d374b7-58ea-4928-a312-31984def293b",
        "origin": "stores:8081",
        "destination": "*:**"
      }
      },
      {
      "timestamp": "2015-11-26T10:24:41.864+0000",
      "info": {
        "signal": "spring.cloud.bus.sent",
        "type": "RefreshRemoteApplicationEvent",
        "id": "c4d374b7-58ea-4928-a312-31984def293b",
        "origin": "customers:9000",
        "destination": "*:**"
      }
      },
      {
      "timestamp": "2015-11-26T10:24:41.862+0000",
      "info": {
        "signal": "spring.cloud.bus.ack",
        "type": "RefreshRemoteApplicationEvent",
        "id": "c4d374b7-58ea-4928-a312-31984def293b",
        "origin": "customers:9000",
        "destination": "*:**"
      }
    }

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本文源码下载：   
[https://github.com/forezp/SpringCloudLearning/tree/master/chapter8][https_github.com_forezp_SpringCloudLearning_tree_master_chapter8]

### 五、参考资料 ###

[spring\_cloud\_bus][spring_cloud_bus]

[rabbitmq]: http://www.rabbitmq.com/
[http_localhost_8881_hi]: http://localhost:8881/hi
[http_localhost_8882_hi]: http://localhost:8882/hi
[Link 1]: https://github.com/forezp/SpringcloudConfig/blob/master/respo/config-client-dev.properties
[http_localhost_8881_bus_refresh]: http://localhost:8881/bus/refresh
[Paste_Image.png]: /images/20220531/29dcc6e9998a4eafbe9e1f69153aef6e.png
[Paste_Image.png 1]: /images/20220531/3340671c9ab943458ca9e1668ea89121.png
[Paste_Image.png 2]: /images/20220531/c40c7f8a0cb7440e8d58685d23762259.png
[https_github.com_forezp_SpringCloudLearning_tree_master_chapter8]: https://github.com/forezp/SpringCloudLearning/tree/master/chapter8
[spring_cloud_bus]: http://projects.spring.io/spring-cloud/spring-cloud.html#_spring_cloud_bus