ActiveMQ並發問題-多個使用者使用隊列中的同一條消息

Question

我使用的是Spring JMS和ActiveMQ，我有一個將消息推送到Queue的客戶端，並且我有多個使用方線程正在偵聽和從Queue中刪除消息。 有時， 相同的消息會由兩個使用者從隊列中出隊。 我不希望出現這種情況，並希望確保只有一個使用者線程可以處理僅一條消息。 關於我哪里出錯了的任何想法？

Spring 3.2.2配置：

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
    <context:annotation-config />
    <context:component-scan base-package="com.myapp" />

    <!-- JMS ConnectionFactory config Starts -->
    <bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
        <property name="brokerURL">
            <value>${brokerURL}</value>
        </property>
        <property name="userName" value="${username}" />
        <property name="password" value="${password}" />
    </bean>

    <bean id="pooledJmsConnectionFactory" class="org.apache.activemq.pool.PooledConnectionFactory"
        init-method="start" destroy-method="stop">
        <property name="connectionFactory" ref="jmsConnectionFactory" />
    </bean>
    <!-- JMS ConnectionFactory config Ends -->

    <!-- JMS Template config Starts -->
    <bean id="myQueue" class="org.apache.activemq.command.ActiveMQQueue">
        <constructor-arg value="${activemq.consumer.destinationName}" />
    </bean>

    <bean id="myQueueTemplate" class="org.springframework.jms.core.JmsTemplate">
        <property name="connectionFactory" ref="pooledJmsConnectionFactory" />
    </bean>
    <!-- JMS Template config Ends -->

    <!-- JMS Listener config starts -->
    <bean id="simpleMessageConverter"
        class="org.springframework.jms.support.converter.SimpleMessageConverter" />

    <bean id="myContainer" 
        class="org.springframework.jms.listener.DefaultMessageListenerContainer">
        <property name="concurrentConsumers" value="${threadcount}" />
        <property name="connectionFactory" ref="pooledJmsConnectionFactory" />
        <property name="destination" ref="myQueue" />
        <property name="messageListener" ref="myListener" />
        <property name="messageSelector" value="JMSType = 'New'" />
    </bean>

    <bean id="myListener"
        class="org.springframework.jms.listener.adapter.MessageListenerAdapter">
        <constructor-arg>
            <bean class="myapp.MessageListener" />
        </constructor-arg>
        <property name="defaultListenerMethod" value="receive" />
        <property name="messageConverter" ref="simpleMessageConverter" />
    </bean>
    <!-- JMS Listener config Ends -->


    <!-- enable the configuration of transactional behavior based on annotations -->
    <bean id="myJMSMessageSender" class="myapp.JMSMessageSender">
        <property name="jmsTemplate" ref="myQueueTemplate" />
        <property name="jmsQueue" ref="myQueue" />
        <property name="messageConverter" ref="simpleMessageConverter" />
    </bean>


    <bean id="myQueueTemplate" class="org.springframework.jms.core.JmsTemplate">
        <property name="connectionFactory" ref="pooledJmsConnectionFactory" />
    </bean>

</beans>

ActiveMQ 5.9.1配置：

<broker xmlns="http://activemq.apache.org/schema/core" brokerName="instance8161" dataDirectory="${activemq.data}" persistent="false">

        <destinationPolicy>
            <policyMap>
              <policyEntries>
                <policyEntry topic="&gt;">
                    <!-- The constantPendingMessageLimitStrategy is used to prevent
                         slow topic consumers to block producers and affect other consumers
                         by limiting the number of messages that are retained
                         For more information, see:

                         http://activemq.apache.org/slow-consumer-handling.html

                    -->
                  <pendingMessageLimitStrategy>
                    <constantPendingMessageLimitStrategy limit="1000"/>
                  </pendingMessageLimitStrategy>
                </policyEntry>
              </policyEntries>
            </policyMap>
        </destinationPolicy>

        ... <!-- rest is default ActiveMQ Config -->
</broker>

Answer 1

最有可能的是，您的myapp.MessageListener （或其依賴項之一）不是線程安全的，並且您會看到使用方線程之間的串擾。

最佳實踐是將您的偵聽器設置為無狀態的（類中沒有突變的字段）。 如果不可能，則需要使用鎖保護共享變量。