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Spring Cloud 消息总线

image-20210303164115071

回顾 Spring 事件/监听

package com.springcloud.event;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.EventListener;

/**
 * Spring 事件 Demo
 *
 * @author <a href="mailto:[email protected]">Finen</a>
 * @see
 * @since
 */
public class SpringEventDemo {
    public static void main(String[] args) {

        // 创建 Annotation 驱动的 Spring 应用上下文
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();

        // 注册EventConfiguration 到 Spring 应用上下文
        context.register(EventConfiguration.class);

        // 启动上下文
        context.refresh();

        ApplicationEventPublisher publisher = context;

        // 发布事件
        publisher.publishEvent(new MyApplicationEvent("hello,world!"));

    }

    private static class MyApplicationEvent extends ApplicationEvent {

        private static final long serialVersionUID = -6069222587522433395L;

        public MyApplicationEvent(String source) {
            super(source);
        }
    }


    @Configuration
    public static class EventConfiguration {

        /**
         * 监听 {@link MyApplicationEvent}
         * @param event {@link MyApplicationEvent}
         */
        @EventListener
        public void onEvent(MyApplicationEvent event) {
            System.out.println("监听到事件： " + event);
        }
    }
}

Spring Cloud Bus

改造 user-service-client : 使用 AMQP 整合 Spring Cloud Bus

增加 Maven 依赖

        <!-- 整合 Spring Cloud Bus : AMQP -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bus-amqp</artifactId>
        </dependency>
启动依赖服务

user-service-client 依赖：

  • Eureka Server (1000)
  • Config Server (7070)
  • Rabbit MQ (5672)

事件传播

如何定位 Application Context ID？

  1. 失效管理端安全 - management.security.enabled = false

  2. 通过访问 http://localhost:8080/beans 确认当前 Application Context ID

    {
    "context": "user-service-client:8080",
    "parent": "user-service-client",
    "beans": []
}

    Application Context ID : user-service-client:8080

单点传播

POST http://localhost:8080/bus/refresh?destination=user-service-client:8080

执行 curl：

curl -X POST http://localhost:8080/bus/refresh?destination=user-service-client:8080

日志输出：

INFO 28041 --- [nio-8080-exec-3] o.s.cloud.bus.event.RefreshListener      : Received remote refresh request. Keys refreshed []
集群传播

POST http://localhost:8080/bus/refresh?destination=user-service-client:**

执行 curl：

curl -X POST http://localhost:8080/bus/refresh?destination=user-service-client:**

日志输出：

INFO 28041 --- [nio-8080-exec-5] o.s.cloud.bus.event.RefreshListener      : Received remote refresh request. Keys refreshed []

通过日志可知事件监听器均为：org.springframework.cloud.bus.event.RefreshListener:

public class RefreshListener
		implements ApplicationListener<RefreshRemoteApplicationEvent> {

	private static Log log = LogFactory.getLog(RefreshListener.class);

	private ContextRefresher contextRefresher;

	public RefreshListener(ContextRefresher contextRefresher) {
		this.contextRefresher = contextRefresher;
	}

	@Override
	public void onApplicationEvent(RefreshRemoteApplicationEvent event) {
		Set<String> keys = contextRefresher.refresh();
		log.info("Received remote refresh request. Keys refreshed " + keys);
	}
}

RefreshListener 监听事件 RefreshRemoteApplicationEvent

自定义 RefreshRemoteApplicationEvent 监听器
@Configuration
public class BusConfiguration {

    @EventListener
    public void onRefreshRemoteApplicationEvent(RefreshRemoteApplicationEvent event) {

        System.out.printf(" Source : %s , originService : %s , destinationService : %s \n",
                event.getSource(),
                event.getOriginService(),
                event.getDestinationService());

    }
}

事件跟踪

默认事件跟踪功能是失效，需要通过配置项激活：spring.cloud.bus.trace.enabled=true

端点：/trace

事件跟踪详情
  {
    "timestamp": 1513517631139,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "RefreshRemoteApplicationEvent",
      "id": "938c1305-02b8-4697-9ac4-5996908eb58d",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:**"
    }
  },
  {
    "timestamp": 1513517631138,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "938c1305-02b8-4697-9ac4-5996908eb58d",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:**"
    }
  }
内部事件类型
  • RefreshRemoteApplicationEvent
  • EnvironmentChangeRemoteApplicationEvent
  • AckRemoteApplicationEvent : ack 激活
自定义 EnvironmentChangeRemoteApplicationEvent 监听
    @EventListener
    public void onEnvironmentChangeRemoteApplicationEvent(EnvironmentChangeRemoteApplicationEvent event) {

        System.out.printf("EnvironmentChangeRemoteApplicationEvent - " +
                        " Source : %s , originService : %s , destinationService : %s \n",
                event.getSource(),
                event.getOriginService(),
                event.getDestinationService());

    }

POST 请求 /bus-env:

curl -X POST http://localhost:8080/bus-env

控制台输出：

EnvironmentChangeRemoteApplicationEvent -  Source : org.springframework.cloud.bus.endpoint.EnvironmentBusEndpoint@656c356c , originService : user-service-client:8080 , destinationService : ** 
2017-12-17 21:40:42.440  INFO 33364 --- [nio-8080-exec-3] o.s.c.b.event.EnvironmentChangeListener  : Received remote environment change request. Keys/values to update {}

EnvironmentChangeListener 是默认的EnvironmentChangeRemoteApplicationEvent 监听器实现

/trace 的变化:

  {
    "timestamp": 1513518042463,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "EnvironmentChangeRemoteApplicationEvent",
      "id": "1af8f5a0-6d1f-440a-82cd-e09876977d33",
      "origin": "user-service-client:8080",
      "destination": "**:**"
    }
  },
  {
    "timestamp": 1513518042462,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "EnvironmentChangeRemoteApplicationEvent",
      "id": "1af8f5a0-6d1f-440a-82cd-e09876977d33",
      "origin": "user-service-client:8080",
      "destination": "**"
    }
  },
举例说明

单机：http://localhost:8080/bus/refresh?destination=user-service-client:8080

集群：http://localhost:8080/bus/refresh?destination=user-service-client:**

本地：http://localhost:8080/refresh

user-service-client 应用，它有三台服务实例 8080、 8081和8082，Application Context 分别 ：

  • user-service-client:8080
  • user-service-client:8081
  • user-service-client:8082

广播集群事件：curl -X POST http://localhost:8080/bus/refresh?destination=user-service-client:**

http://localhost:8080/trace：

  {
    "timestamp": 1513519229726,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "dbb44a68-1edb-49fd-ac20-fc19669d7c75",
      "origin": "user-service-client:8081",
      "destination": "user-service-client:**"
    }
  },
  {
    "timestamp": 1513519226752,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "RefreshRemoteApplicationEvent",
      "id": "dbb44a68-1edb-49fd-ac20-fc19669d7c75",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:**"
    }
  },
  {
    "timestamp": 1513519226751,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "dbb44a68-1edb-49fd-ac20-fc19669d7c75",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:**"
    }
  },

http://localhost:8081/trace：

  {
    "timestamp": 1513519229726,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "RefreshRemoteApplicationEvent",
      "id": "dbb44a68-1edb-49fd-ac20-fc19669d7c75",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:**"
    }
  },
  {
    "timestamp": 1513519229724,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "dbb44a68-1edb-49fd-ac20-fc19669d7c75",
      "origin": "user-service-client:8081",
      "destination": "user-service-client:**"
    }
  },

传播单点事件：curl -X POST http://localhost:8080/bus/refresh?destination=user-service-client:8081

事件源：8080

  {
    "timestamp": 1513519487670,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "6cbc9711-d1a5-4cce-b65c-098f8a6e41d5",
      "origin": "user-service-client:8081",
      "destination": "user-service-client:8081:**"
    }
  },
  {
    "timestamp": 1513519484687,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "RefreshRemoteApplicationEvent",
      "id": "6cbc9711-d1a5-4cce-b65c-098f8a6e41d5",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:8081:**"
    }
  }

监听者：8081

  {
    "timestamp": 1513519487665,
    "info": {
      "signal": "spring.cloud.bus.sent",
      "type": "RefreshRemoteApplicationEvent",
      "id": "6cbc9711-d1a5-4cce-b65c-098f8a6e41d5",
      "origin": "user-service-client:8080",
      "destination": "user-service-client:8081:**"
    }
  },
  {
    "timestamp": 1513519487664,
    "info": {
      "signal": "spring.cloud.bus.ack",
      "event": "RefreshRemoteApplicationEvent",
      "id": "6cbc9711-d1a5-4cce-b65c-098f8a6e41d5",
      "origin": "user-service-client:8081",
      "destination": "user-service-client:8081:**"
    }
  }

源码分析

BusAutoConfiguration
监听 Spring Event（本地事件）
	@EventListener(classes = RemoteApplicationEvent.class)
	public void acceptLocal(RemoteApplicationEvent event) {
		if (this.serviceMatcher.isFromSelf(event)
				&& !(event instanceof AckRemoteApplicationEvent)) {
			this.cloudBusOutboundChannel.send(MessageBuilder.withPayload(event).build());
		}
	}

由于@EventListener 监听 Spring Event，事件RemoteApplicationEvent 属于本地事件，因此必然有发布该事件的源头。

监听 Stream 事件（远程事件）
	@StreamListener(SpringCloudBusClient.INPUT)
	public void acceptRemote(RemoteApplicationEvent event) {
		if (event instanceof AckRemoteApplicationEvent) {
			if (this.bus.getTrace().isEnabled() && !this.serviceMatcher.isFromSelf(event)
					&& this.applicationEventPublisher != null) {
				this.applicationEventPublisher.publishEvent(event);
			}
			// If it's an ACK we are finished processing at this point
			return;
		}
		if (this.serviceMatcher.isForSelf(event)
				&& this.applicationEventPublisher != null) {
			if (!this.serviceMatcher.isFromSelf(event)) {
				this.applicationEventPublisher.publishEvent(event);
			}
			if (this.bus.getAck().isEnabled()) {
				AckRemoteApplicationEvent ack = new AckRemoteApplicationEvent(this,
						this.serviceMatcher.getServiceId(),
						this.bus.getAck().getDestinationService(),
						event.getDestinationService(), event.getId(), event.getClass());
				this.cloudBusOutboundChannel
						.send(MessageBuilder.withPayload(ack).build());
				this.applicationEventPublisher.publishEvent(ack);
			}
		}
		if (this.bus.getTrace().isEnabled() && this.applicationEventPublisher != null) {
			// We are set to register sent events so publish it for local consumption,
			// irrespective of the origin
			this.applicationEventPublisher.publishEvent(new SentApplicationEvent(this,
					event.getOriginService(), event.getDestinationService(),
					event.getId(), event.getClass()));
		}
	}

acceptRemote 监听 Stream 事件，同时发送 Spring Event（本地事件）。

ServiceMatcher#isForSelf(RemoteApplicationEvent) 用于匹配 RemoteApplicationEvent 是否为当前应用实例而来。

this.serviceMatcher.isForSelf(event)

ServiceMatcher#isFromSelf(RemoteApplicationEvent) 用于判断当前事件是否为自己发送。

this.serviceMatcher.isFromSelf(event)
整体流程

假设 user-service-client:8080 执行/bus/refresh 端口，发送了一个RefreshRemoteApplicationEvent事件:

curl -X POST http://localhost:8080/bus/refresh?destination=user-service-client:8082

user-service-client:8080 : Bus 事件的发布者、监听者

user-service-client:8081 : Bus 事件监听者

user-service-client:8082: Bus 事件监听者

当 Stream Binder 接收到发布者RefreshRemoteApplicationEvent事件，广播该事件到所有的监听者：

  • user-service-client:8080 : 判断事件是自己发送，SentApplicationEvent

  • user-service-client:8081：判断事件不是为自己发送，忽略

  • user-service-client:8082：判断事件是为自己发送，执行RefreshRemoteApplicationEvent 事件监听。如果 ack 激活的，cloudBusOutboundChannel 会发送AckRemoteApplicationEvent 到管道里。可以由：

        @StreamListener(SpringCloudBusClient.OUTPUT)
    public void onAckRemoteApplicationEvent(AckRemoteApplicationEvent event) {}

    自定义实现 RemoteApplicationEvent

扩展 RemoteApplicationEvent ：UserRemoteApplicationEvent
package com.springcloud.lesson14.user.service.client.bus;

import com.springcloud.lesson14.domain.User;
import org.springframework.cloud.bus.event.RemoteApplicationEvent;

/**
 * 自定义事件
 *
 * @author <a href="mailto:[email protected]">Finen</a>
 * @see
 * @since
 */
public class UserRemoteApplicationEvent extends RemoteApplicationEvent {
    private static final long serialVersionUID = 7549594113210834670L;

    public UserRemoteApplicationEvent(User user, String originService,
                                      String destinationService) {
        super(user, originService, destinationService);
    }
}
添加 @RemoteApplicationEventScan
@Configuration
@RemoteApplicationEventScan(basePackageClasses = UserRemoteApplicationEvent.class)
public class BusConfiguration {
}
发布 UserRemoteApplicationEvent
package com.springcloud.lesson14.user.service.client.web.controller;

import com.springcloud.lesson14.domain.User;
import com.springcloud.lesson14.user.service.client.bus.UserRemoteApplicationEvent;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * TODO
 *
 * @author <a href="mailto:[email protected]">Finen</a>
 * @see
 * @since
 */
@RestController
public class BusEventController implements ApplicationContextAware, ApplicationEventPublisherAware {

    private ApplicationEventPublisher eventPublisher;

    private ApplicationContext applicationContext;

    @PostMapping("/bus/event/publish/user")
    public boolean publishUserEvent(@RequestBody User user,
                                    @RequestParam(value = "destination", required = false) String destination) {
        String serviceInstanced = applicationContext.getId();
        UserRemoteApplicationEvent event = new UserRemoteApplicationEvent(user, serviceInstanced, destination);
        eventPublisher.publishEvent(event);
        return true;
    }

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.eventPublisher = applicationEventPublisher;

    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
}
监听 UserRemoteApplicationEvent
    @EventListener
    public void onUserRemoteApplicationEvent(UserRemoteApplicationEvent event) {

        System.out.printf("UserRemoteApplicationEvent - " +
                        " Source : %s , originService : %s , destinationService : %s \n",
                event.getSource(),
                event.getOriginService(),
                event.getDestinationService());
    }
测试 UserRemoteApplicationEvent

Postman http://localhost:8080/bus/event/publish/user?destination=user-service-client:8081

POST JSON data：

{
    "id":3,
    "name": "xiaoming"
}