Rabbitmq消费端消息消费幂等性的优化与手动ACK

如果重复的消息同时进来的话，我们就要进行消息幂等性的校验，使其只消费一条消息，使得消息不会被重复消费，并且手动确认消息（ACK）保证队列中的消息被成功消费

解决方案：
对于mysql在高并发情况下存在的性能瓶颈，这里使用redis缓存，把消费过的消息id存入redis中，每次消费消息前，检查redis中是否存在该消息id，如果存在则证明被消费过不再消费，不存在则直接返回。

1.开启手动确认

  rabbitmq:
    username: guest
    password: guest
    host: 8.140.157.58
    port: 5672
    #开启手动确认
    listener:
     simple:
      acknowledge-mode: manual

2.消费者模块引入redis并配置

  redis:
    host: 8.140.157.58
    port: 6379
    database: 0
    password: yyx10033016
    timeout: 10000ms
    lettuce:
      pool:
        min-idle: 5
        max-idle: 200
        max-active: 1024
        max-wait: 10000ms

3.修改消费者模块

@Component
public class MailReceiver {
    private static final Logger LOGGER = LoggerFactory.getLogger(MailReceiver.class);

    @Resource
    private JavaMailSender javaMailSender;
    @Resource
    private MailProperties mailProperties;
    @Resource
    private TemplateEngine templateEngine;
    @Autowired
    private RedisTemplate redisTemplate;

    @RabbitListener(queues = MailConstants.QUEUE)
    public void handler(Message message, Channel channel){
        Employee employee = (Employee) message.getPayload();
        MessageHeaders headers = message.getHeaders();
        //消息序号
        long tag = (long) headers.get(AmqpHeaders.DELIVERY_TAG);
        String msgId = (String) headers.get("spring_returned_message_correlation");
        HashOperations hashOperations = redisTemplate.opsForHash();
        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
        MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMessage);
        try {
            if (hashOperations.entries("mail_log").containsKey(msgId)){
                LOGGER.error("消息已将被消费=============>",msgId);
                /*
                手动确认消息
                tag:消息序号
                multiple:false 是否确认多条
                 */
                channel.basicAck(tag,false);
                return;
            }

            //发件人
            mimeMessageHelper.setFrom(mailProperties.getUsername());
            //收件人
            mimeMessageHelper.setTo(employee.getEmail());
            //主题
            mimeMessageHelper.setSubject("入职欢迎邮件");
            //发送日期
            mimeMessageHelper.setSentDate(new Date());
            //邮件发送内容
            Context context = new Context();
            context.setVariable("name",employee.getName());
            context.setVariable("posName",employee.getPositionName());
            context.setVariable("joblevelName",employee.getJoblevelName());
            context.setVariable("departmentName",employee.getDepartmentName());
            String mail = templateEngine.process("mail", context);
            mimeMessageHelper.setText(mail,true);
            //发送邮件
            javaMailSender.send(mimeMessage);
            LOGGER.info("mail发送成功！");
            //将消息id存入redis中
            hashOperations.put("mail_log",msgId,"ok");
            //手动确认消息
            channel.basicAck(tag,false);
        } catch (Exception e) {
            try {
                //true  是否退回队列
                channel.basicNack(tag,false,true);
            } catch (IOException ioException) {
                LOGGER.error("邮件发送失败======>",e.getMessage());
            }
            LOGGER.error("邮件发送失败======>",e.getMessage());
        }
    }

}