关于#RabbitMQ#的Unacked问题，如何解决？

Question

问题遇到的现象和发生背景

RabbitMQ 出现Unacked，且消费端未监听到消息，消费端配置 手动ack，

Unacked 只是偶尔出现，重启消费端后正常

消费端配置如下

<rabbit:connection-factory id="rabbitMqConnectionFactory" thread-factory="tf" host="${rabbit.host}" port="${rabbit.port}"
                               username="${rabbit.user}" password="${rabbit.pass}"/>

    <rabbit:admin connection-factory="rabbitMqConnectionFactory" />

    <bean id="tf" class="org.springframework.scheduling.concurrent.CustomizableThreadFactory">
        <constructor-arg value="rabbitmq-" />
    </bean>

    <rabbit:queue name="${rabbit.monitor.down.queue}" auto-declare="true" />

    <rabbit:direct-exchange id="fedExchange" name="fedExchange">
        <rabbit:bindings>
            <rabbit:binding queue="${rabbit.monitor.down.queue}" key="${rabbit.monitor.down.key}"/>
        </rabbit:bindings>
    </rabbit:direct-exchange>

    <bean id ="rabbitExecutor"  class ="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor" >
        <property name ="corePoolSize" value ="30" /><!-- 线程池维护线程的最少数量 -->
        <property name ="maxPoolSize" value ="200" /><!-- 线程池维护线程的最大数量 -->
        <property name ="queueCapacity" value ="50" /><!-- 线程池所使用的缓冲队列 -->
        <property name ="keepAliveSeconds" value ="30" /><!-- 线程池维护线程所允许的空闲时间-->
    </bean>

    <!--prefetch="1" 一个线程预取数量设置为1 -->
    <rabbit:listener-container connection-factory="rabbitMqConnectionFactory" acknowledge="manual"
                               task-executor="rabbitExecutor" concurrency="5" prefetch="1">
        <rabbit:listener response-exchange="fedExchange" queues="${rabbit.monitor.down.queue}" ref="monitorDownListener" />
    </rabbit:listener-container>