Master Spring Cloud Bus: Dynamic Config Refresh with RabbitMQ

Spring Cloud Bus Overview

Spring Cloud Bus uses a lightweight message broker to connect services in a microservice architecture, allowing broadcast of state changes such as configuration updates. It works with Spring Cloud Config to enable dynamic configuration refresh and supports RabbitMQ and Kafka; the example below uses RabbitMQ.

RabbitMQ Installation

Install Erlang (download from http://erlang.org/download/otp_win64_21.3.exe ).

Install RabbitMQ (download from https://dl.bintray.com/rabbitmq/all/rabbitmq-server/3.7.14/rabbitmq-server-3.7.14.exe ).

Navigate to the

sbin

directory of the RabbitMQ installation.

Open a command line and enable the management plugin:

<code>rabbitmq-plugins enable rabbitmq_management</code>

Visit http://localhost:15672/ and log in with username

guest

and password

guest

.

Dynamic Configuration Refresh

Dynamic refresh requires Spring Cloud Config. The example uses the config‑server and config‑client modules from the previous lesson.

Add Bus Support to config‑server

Add dependencies to

pom.xml

:

<code>&lt;dependency&gt;
    &lt;groupId&gt;org.springframework.cloud&lt;/groupId&gt;
    &lt;artifactId&gt;spring-cloud-starter-bus-amqp&lt;/artifactId&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
    &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
    &lt;artifactId&gt;spring-boot-starter-actuator&lt;/artifactId&gt;
&lt;/dependency&gt;</code>

Create

application-amqp.yml

with RabbitMQ settings and expose the

bus-refresh

actuator endpoint.

<code>server:
  port: 8904
spring:
  application:
    name: config-server
  cloud:
    config:
      server:
        git:
          uri: https://gitee.com/macrozheng/springcloud-config.git
          username: macro
          password: 123456
          clone-on-start: true
    rabbitmq:
      host: localhost
      port: 5672
      username: guest
      password: guest
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8001/eureka/
management:
  endpoints:
    web:
      exposure:
        include: 'bus-refresh'</code>

Add Bus Support to config‑client

Add the same

spring-cloud-starter-bus-amqp

dependency to the client’s

pom.xml

.

<code>&lt;dependency&gt;
    &lt;groupId&gt;org.springframework.cloud&lt;/groupId&gt;
    &lt;artifactId&gt;spring-cloud-starter-bus-amqp&lt;/artifactId&gt;
&lt;/dependency&gt;</code>

Create two bootstrap files (

bootstrap-amqp1.yml

and

bootstrap-amqp2.yml

) for two client instances with different ports.

<code>server:
  port: 9004
spring:
  application:
    name: config-client
  cloud:
    config:
      profile: dev
      label: dev
      name: config
      discovery:
        enabled: true
        service-id: config-server
    rabbitmq:
      host: localhost
      port: 5672
      username: guest
      password: guest
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8001/eureka/
management:
  endpoints:
    web:
      exposure:
        include: 'refresh'</code>

Demonstration

Start Eureka server, config‑server (using

application-amqp.yml

), and the two config‑clients.

In the RabbitMQ console, a

springCloudBus

exchange and three queues prefixed with

springCloudBus.anonymous

are created.

Modify

config-dev.yml

in the Git repository (change

config.info

value).

<code># before
config:
  info: "config info for dev(dev)"
# after
config:
  info: "update config info for dev(dev)"</code>

Trigger a refresh for all services via http://localhost:8904/actuator/bus-refresh . The updated value appears when calling

http://localhost:9004/configInfo

and

http://localhost:9005/configInfo

:

<code>update config info for dev(dev)</code>

To refresh a specific instance, call

http://localhost:8904/actuator/bus-refresh/{destination}

, e.g.,

http://localhost:8904/actuator/bus-refresh/config-client:9004

.

Using WebHooks

Configure a Gitee webhook to invoke the bus‑refresh endpoint whenever code is pushed to the configuration repository, enabling automatic configuration updates.

Modules Used

<code>springcloud-learning
├── eureka-server   // Eureka registration center
├── config-server   // Configuration center service
└── config-client   // Client services that fetch configuration</code>

Project Source Code

https://github.com/macrozheng/springcloud-learning