RabbitMQ整合Spring Booot【消费者补偿幂等问题】

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byte01 2022-10-24 14:28:28
文章标签 spring json apache 文章分类 运维
如果消费者 运行时候 报错了
package com.toov5.msg.SMS;

import org.springframework.amqp.rabbit.annotation.RabbitHandler;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;

@Component 
@RabbitListener(queues="fanout_sms_queue")   
public class SMSConsumer {

    @RabbitHandler  
   public void process(String mString) {
       System.out.println("短信消费者获取生产者消息msg"+mString);
       int i = 1/0;
   }
}
当生产者投递消息后：消费者会不停的进行打印:
 
 
 消息一直没有被消费
 
原因 Rabbitmq 默认情况下 如果消费者程序出现异常情况 会自动实现补偿机制  也就是 重试机制
 
@RabbitListener底层使用AOP进行拦截，如果程序没有抛出异常，自动提交事务。 如果Aop使用异常通知 拦截获取异常信息的话 ， 自动实现补偿机制，该消息会一直缓存在Rabbitmq服务器端进行重放，一直重试到不抛出异常为准。
 可以修改重试策略
 一般来说默认5s重试一次，
消费者配置：
 listener:
      simple:
        retry:
        ####开启消费者重试
          enabled: true
         ####最大重试次数（默认无数次）
          max-attempts: 5
        ####重试间隔次数
          initial-interval: 3000
效果： 充实5次 不行就放弃了 
 
 
 
 
 MQ重试机制机制 需要注意的问题
  
如何合适选择重试机制
 
情况1:  消费者获取到消息后，调用第三方接口，但接口暂时无法访问，是否需要重试?      需要重试   别人的问题不是我自己的问题
 
情况2:  消费者获取到消息后，抛出数据转换异常，是否需要重试?                                      不需要重试   充实一亿次也是如此 木有必要  需要发布版本解决
总结：对于情况2，如果消费者代码抛出异常是需要发布新版本才能解决的问题，那么不需要重试，重试也无济于事。应该采用 日志记录+定时任务job健康检查+人工进行补偿
           把错误记录在日志里面，通过定时Job去自动的补偿，或通过人工去补偿。 
 
 传统的HTTP请求 如果失败了 没法自动重试  当然自己可以写个循环实现
 MQ完全自己自带的
 
 
情况2的拓展延申：
    将之前的案例改为   邮件消费者 调用邮件第三方接口 
 
   伪代码：
    在consumer 中 调用接口后 判断返回值  由于RabbitMQ 在消费者异常时候 会进行重试机制 进行补偿 
    所以可以抛出个异常 来实现
   
Consumer：
              String result   =   template.Email();
             if(result == null){
                   throw new Exception("调用第三方邮件服务器接口失败!");
               }
 
 
producer：
 
pom:
<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.itmayiedu</groupId>
    <artifactId>rabbitmq_producer_springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>
    <dependencies>

        <!-- springboot-web组件 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- 添加springboot对amqp的支持 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
        <!--fastjson -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.49</version>
        </dependency>
    </dependencies>
</project>
config:package com.itmayiedu.rabbitmq.config;

import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.FanoutExchange;
import org.springframework.amqp.core.Queue;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

//Fanout 类型 发布订阅模式
@Component
public class FanoutConfig {

    // 邮件队列
    private String FANOUT_EMAIL_QUEUE = "fanout_email_queue";

    // 短信队列
    private String FANOUT_SMS_QUEUE = "fanout_sms_queue";
    // fanout 交换机
    private String EXCHANGE_NAME = "fanoutExchange";

    // 1.定义邮件队列
    @Bean
    public Queue fanOutEamilQueue() {
        return new Queue(FANOUT_EMAIL_QUEUE);
    }

    // 2.定义短信队列
    @Bean
    public Queue fanOutSmsQueue() {
        return new Queue(FANOUT_SMS_QUEUE);
    }

    // 2.定义交换机
    @Bean
    FanoutExchange fanoutExchange() {
        return new FanoutExchange(EXCHANGE_NAME);
    }

    // 3.队列与交换机绑定邮件队列
    @Bean
    Binding bindingExchangeEamil(Queue fanOutEamilQueue, FanoutExchange fanoutExchange) {
        return BindingBuilder.bind(fanOutEamilQueue).to(fanoutExchange);
    }

    // 4.队列与交换机绑定短信队列
    @Bean
    Binding bindingExchangeSms(Queue fanOutSmsQueue, FanoutExchange fanoutExchange) {
        return BindingBuilder.bind(fanOutSmsQueue).to(fanoutExchange);
    }
}
  Producer:
package com.itmayiedu.rabbitmq;

import java.util.UUID;

import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageBuilder;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.alibaba.fastjson.JSONObject;

@Component
public class FanoutProducer {
    @Autowired
    private AmqpTemplate amqpTemplate;

    public void send(String queueName) {
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("email", "xx@163.com");
        jsonObject.put("timestamp", System.currentTimeMillis());
        String jsonString = jsonObject.toJSONString();
        System.out.println("jsonString:" + jsonString);
        // 设置消息唯一id 保证每次重试消息id唯一
        /*Message message = MessageBuilder.withBody(jsonString.getBytes())
                .setContentType(MessageProperties.CONTENT_TYPE_JSON).setContentEncoding("utf-8")
                .setMessageId(UUID.randomUUID() + "").build();*/
        amqpTemplate.convertAndSend(queueName, jsonString);
    }
}
Controller:package com.itmayiedu.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.itmayiedu.rabbitmq.FanoutProducer;

@RestController
public class ProducerController {
    @Autowired
    private FanoutProducer fanoutProducer;

    @RequestMapping("/sendFanout")
    public String sendFanout(String queueName) {
        fanoutProducer.send(queueName);
        return "success";
    }
}
yml:spring:
  rabbitmq:
  ####连接地址
    host: 192.168.91.6
   ####端口号   
    port: 5672
   ####账号 
    username: admin
   ####密码  
    password: admin
   ### 地址
    virtual-host: /admin_toov5
启动类：package com.itmayiedu;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class AppProducer {

    public static void main(String[] args) {
        SpringApplication.run(AppProducer.class, args);
    }

}
 Consumer：
pom:
<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.itmayiedu</groupId>
    <artifactId>rabbitmq_consumer_springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>
    <dependencies>

        <!-- springboot-web组件 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- 添加springboot对amqp的支持 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
        <!--fastjson -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.49</version>
        </dependency>

    </dependencies>
</project>
  utils:
package com.itmayiedu.rabbitmq.utils;

import com.alibaba.fastjson.JSONObject;
import org.apache.http.HttpEntity;
import org.apache.http.HttpStatus;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

/**
 * HttpClient4.3工具类
 * 
 * @author hang.luo
 */
public class HttpClientUtils {
    private static Logger logger = LoggerFactory.getLogger(HttpClientUtils.class); // 日志记录

    private static RequestConfig requestConfig = null;

    static {
        // 设置请求和传输超时时间
        requestConfig = RequestConfig.custom().setSocketTimeout(2000).setConnectTimeout(2000).build();
    }

    /**
     * post请求传输json参数
     * 
     * @param url
     *            url地址
     * @param json
     *            参数
     * @return
     */
    public static JSONObject httpPost(String url, JSONObject jsonParam) {
        // post请求返回结果
        CloseableHttpClient httpClient = HttpClients.createDefault();
        JSONObject jsonResult = null;
        HttpPost httpPost = new HttpPost(url);
        // 设置请求和传输超时时间
        httpPost.setConfig(requestConfig);
        try {
            if (null != jsonParam) {
                // 解决中文乱码问题
                StringEntity entity = new StringEntity(jsonParam.toString(), "utf-8");
                entity.setContentEncoding("UTF-8");
                entity.setContentType("application/json");
                httpPost.setEntity(entity);
            }
            CloseableHttpResponse result = httpClient.execute(httpPost);
            // 请求发送成功，并得到响应
            if (result.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                String str = "";
                try {
                    // 读取服务器返回过来的json字符串数据
                    str = EntityUtils.toString(result.getEntity(), "utf-8");
                    // 把json字符串转换成json对象
                    jsonResult = JSONObject.parseObject(str);
                } catch (Exception e) {
                    logger.error("post请求提交失败:" + url, e);
                }
            }
        } catch (IOException e) {
            logger.error("post请求提交失败:" + url, e);
        } finally {
            httpPost.releaseConnection();
        }
        return jsonResult;
    }

    /**
     * post请求传输String参数 例如：name=Jack&sex=1&type=2
     * Content-type:application/x-www-form-urlencoded
     * 
     * @param url
     *            url地址
     * @param strParam
     *            参数
     * @return
     */
    public static JSONObject httpPost(String url, String strParam) {
        // post请求返回结果
        CloseableHttpClient httpClient = HttpClients.createDefault();
        JSONObject jsonResult = null;
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);
        try {
            if (null != strParam) {
                // 解决中文乱码问题
                StringEntity entity = new StringEntity(strParam, "utf-8");
                entity.setContentEncoding("UTF-8");
                entity.setContentType("application/x-www-form-urlencoded");
                httpPost.setEntity(entity);
            }
            CloseableHttpResponse result = httpClient.execute(httpPost);
            // 请求发送成功，并得到响应
            if (result.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                String str = "";
                try {
                    // 读取服务器返回过来的json字符串数据
                    str = EntityUtils.toString(result.getEntity(), "utf-8");
                    // 把json字符串转换成json对象
                    jsonResult = JSONObject.parseObject(str);
                } catch (Exception e) {
                    logger.error("post请求提交失败:" + url, e);
                }
            }
        } catch (IOException e) {
            logger.error("post请求提交失败:" + url, e);
        } finally {
            httpPost.releaseConnection();
        }
        return jsonResult;
    }

    /**
     * 发送get请求
     * 
     * @param url
     *            路径
     * @return
     */
    public static JSONObject httpGet(String url) {
        // get请求返回结果
        JSONObject jsonResult = null;
        CloseableHttpClient client = HttpClients.createDefault();
        // 发送get请求
        HttpGet request = new HttpGet(url);
        request.setConfig(requestConfig);
        try {
            CloseableHttpResponse response = client.execute(request);

            // 请求发送成功，并得到响应
            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                // 读取服务器返回过来的json字符串数据
                HttpEntity entity = response.getEntity();
                String strResult = EntityUtils.toString(entity, "utf-8");
                // 把json字符串转换成json对象
                jsonResult = JSONObject.parseObject(strResult);
            } else {
                logger.error("get请求提交失败:" + url);
            }
        } catch (IOException e) {
            logger.error("get请求提交失败:" + url, e);
        } finally {
            request.releaseConnection();
        }
        return jsonResult;
    }

}
consumer:package com.itmayiedu.rabbitmq;

import java.util.Map;

import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.amqp.support.AmqpHeaders;
import org.springframework.messaging.handler.annotation.Headers;
import org.springframework.stereotype.Component;

import com.alibaba.fastjson.JSONObject;
import com.itmayiedu.rabbitmq.utils.HttpClientUtils;
import com.rabbitmq.client.Channel;

//邮件队列
@Component
public class FanoutEamilConsumer {
     @RabbitListener(queues = "fanout_email_queue")
     public void process(String msg) throws Exception {
     System.out.println("邮件消费者获取生产者消息msg:" + msg);
     JSONObject jsonObject = JSONObject.parseObject(msg);
     // 获取email参数
     String email = jsonObject.getString("email");
     // 请求地址
     String emailUrl = "http://127.0.0.1:8083/sendEmail?email=" + email;
     JSONObject result = HttpClientUtils.httpGet(emailUrl);
     if (result == null) {
     // 因为网络原因,造成无法访问,继续重试
     throw new Exception("调用接口失败!");
     }
     System.out.println("执行结束....");

     }
}
yml:spring:
  rabbitmq:
  ####连接地址
    host: 192.168.91.6
   ####端口号   
    port: 5672
   ####账号 
    username: admin
   ####密码  
    password: admin
   ### 地址
    virtual-host: /admin_toov5
    listener: 
      simple:
        retry:
        ####开启消费者异常重试
          enabled: true
         ####最大重试次数
          max-attempts: 5
        ####重试间隔次数
          initial-interval: 2000


server:
  port: 8081
 启动类：
package com.itmayiedu.rabbitmq;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class AppConsumer {

    public static void main(String[] args) {
        SpringApplication.run(AppConsumer.class, args);
    }

}
  邮件服务器：
package com.mayikt.controller;

import java.util.HashMap;
import java.util.Map;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class MsgController {

    // 模拟第三方发送邮件
    @RequestMapping("/sendEmail")
    public Map<String, Object> sendEmail(String email) {
        System.out.println("开始发送邮件:" + email);
        Map<String, Object> result = new HashMap<String, Object>();
        result.put("code", "200");
        result.put("msg", "发送邮件成功..");
        System.out.println("发送邮件成功");
        return result;
    }

    public static void main(String[] args) {
        SpringApplication.run(MsgController.class, args);
    }

}
yml:server:
  port: 8083
pom:<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.mayikt</groupId>
    <artifactId>mayikt_sms</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>
    <dependencies>

        <!-- springboot-web组件 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- 添加springboot对amqp的支持 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
        <!--fastjson -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.49</version>
        </dependency>

    </dependencies>
</project>
在没有启动邮件服务器时候，消费者 调用接口失败 会一直重试 重试五次在此期间 如果启动成功 则重试成功 不再重试  不再进行补偿机制
 
 
消费者如果保证消息幂等性，不被重复消费
 
产生原因:网络延迟传输中，或者消费出现异常或者是消费延迟，会造成进行MQ重试进行重试补偿机制，在重试过程中，可能会造成重复消费。
 
解决办法:
使用全局MessageID判断消费方使用同一个，解决幂等性。
  
   只要重试过程中，判断如果已经走完了 不能再继续走 继续执行了
   MQ消费者的幂等行的解决 一般使用全局ID  或者写个唯一标识比如时间戳   或者UUID  或者订单号
   
  改进：
  producer：
 添加：
 
// 设置消息唯一id 保证每次重试消息id唯一  
        Message message = MessageBuilder.withBody(jsonString.getBytes())
                .setContentType(MessageProperties.CONTENT_TYPE_JSON).setContentEncoding("utf-8")
                .setMessageId(UUID.randomUUID() + "").build(); //消息id设置在请求头里面 用UUID做全局ID 
        amqpTemplate.convertAndSend(queueName, message);
  全部代码：
  
package com.itmayiedu.rabbitmq;

import java.util.UUID;

import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageBuilder;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.alibaba.fastjson.JSONObject;

@Component
public class FanoutProducer {
    @Autowired
    private AmqpTemplate amqpTemplate;

    public void send(String queueName) {
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("email", "xx@163.com");
        jsonObject.put("timestamp", System.currentTimeMillis());
        String jsonString = jsonObject.toJSONString();
        System.out.println("jsonString:" + jsonString);
        // 设置消息唯一id 保证每次重试消息id唯一  
        Message message = MessageBuilder.withBody(jsonString.getBytes())
                .setContentType(MessageProperties.CONTENT_TYPE_JSON).setContentEncoding("utf-8")
                .setMessageId(UUID.randomUUID() + "").build(); //消息id设置在请求头里面 用UUID做全局ID 
        amqpTemplate.convertAndSend(queueName, message);
    }
}
  同样的 消费者也需要修改：
 方法参数类型为 Message  然后可以获取这个ID 然后可以进行业务逻辑操作
 @RabbitListener(queues = "fanout_email_queue")
     public void process(Message message) throws Exception {
     // 获取消息Id
     String messageId = message.getMessageProperties().getMessageId();  //id获取之
     String msg = new String(message.getBody(), "UTF-8"); //消息内容获取之
     System.out.println("-----邮件消费者获取生产者消息-----------------" + "messageId:" + messageId + ",消息内容:" +
     msg);
     if (messageId == null) {
            return;
        }
     JSONObject jsonObject = JSONObject.parseObject(msg);
     // 获取email参数
     String email = jsonObject.getString("email");
     // 请求地址
     String emailUrl = "http://127.0.0.1:8083/sendEmail?email=" + email;
     JSONObject result = HttpClientUtils.httpGet(emailUrl);
     if (result == null) {
     // 因为网络原因,造成无法访问,继续重试
     throw new Exception("调用接口失败!");
     }
     System.out.println("执行结束....");
     //messId 的情况写入到redis 中  成功就修改为空
     }
  重试机制都是间隔性的  每次都是一个线程  单线程重试
 
 
 关于应答模式：
    Spring boot 中进行 AOP拦截 自动帮助做重试
    手动应答的话 ，如果不告诉服务器已经消费成功，则服务器不会删除 消息。告诉消费成功了才会删除。
    
消费者的yml加入：
 acknowledge-mode: manual 
    spring:
  rabbitmq:
  ####连接地址
    host: 192.168.91.6
   ####端口号   
    port: 5672
   ####账号 
    username: admin
   ####密码  
    password: admin
   ### 地址
    virtual-host: /admin_toov5
    listener: 
      simple:
        retry:
        ####开启消费者异常重试
          enabled: true
         ####最大重试次数
          max-attempts: 5
        ####重试间隔次数
          initial-interval: 2000
        ####开启手动ack  
        acknowledge-mode: manual 

server:
  port: 8081
  
 开启模式之后：
   消费者参数需要加入：  @Headers Map<String, Object> headers, Channel channel
  代码逻辑最后面加入：
// // 手动ack
Long deliveryTag = (Long) headers.get(AmqpHeaders.DELIVERY_TAG);
// 手动签收  告诉RabbitMQ 消费成功了  消息可以删除了
channel.basicAck(deliveryTag, false);   
代码如下：
@RabbitListener(queues = "fanout_email_queue")
    public void process(Message message, @Headers Map<String, Object> headers, Channel channel) throws Exception {
        // 获取消息Id
        String messageId = message.getMessageProperties().getMessageId();
        String msg = new String(message.getBody(), "UTF-8");
        System.out.println("邮件消费者获取生产者消息" + "messageId:" + messageId + ",消息内容:" + msg);
        JSONObject jsonObject = JSONObject.parseObject(msg);
        // 获取email参数
        String email = jsonObject.getString("email");
        // 请求地址
        String emailUrl = "http://127.0.0.1:8083/sendEmail?email=" + email;
        JSONObject result = HttpClientUtils.httpGet(emailUrl);
        if (result == null) {
            // 因为网络原因,造成无法访问,继续重试
            throw new Exception("调用接口失败!");
        }
        // // 手动ack
        Long deliveryTag = (Long) headers.get(AmqpHeaders.DELIVERY_TAG);
        // 手动签收
        channel.basicAck(deliveryTag, false);
        System.out.println("执行结束....");
    }