ActiveMQ持久化消息

ActiveMQ的另一個問題就是只要是軟件就有可能掛掉，掛掉不可怕，怕的是掛掉之后把信息給丟了，所以本節分析一下幾種持久化方式：

一、持久化為文件

ActiveMQ默認就支持這種方式，只要在發消息時設置消息為持久化就可以了。

打開安裝目錄下的配置文件：

D:\ActiveMQ\apache-activemq\conf\activemq.xml在越80行會發現默認的配置項：

        <persistenceAdapter>

            <kahaDB directory="${activemq.data}/kahadb"/>

        </persistenceAdapter>

注意這里使用的是kahaDB，是一個基於文件支持事務的消息存儲器，是一個可靠，高性能，可擴展的消息存儲器。

     他的設計初衷就是使用簡單並盡可能的快。KahaDB的索引使用一個transaction log，並且所有的destination只使用一個index，有人測試表明：如果用於生產環境，支持1萬個active connection，每個connection有一個獨立的queue。該表現已經足矣應付大部分的需求。

然后再發送消息的時候改變第二個參數為：

MsgDeliveryMode.Persistent

Message保存方式有2種
PERSISTENT：保存到磁盤，consumer消費之后，message被刪除。
NON_PERSISTENT：保存到內存，消費之后message被清除。
注意：堆積的消息太多可能導致內存溢出。

然后打開生產者端發送一個消息：

不啟動消費者端，同時在管理界面查看：

發現有一個消息正在等待，這時如果沒有持久化，ActiveMQ宕機后重啟這個消息就是丟失，而我們現在修改為文件持久化，重啟ActiveMQ后消費者仍然能夠收到這個消息。

二、持久化為數據庫

我們從支持Mysql為例，先從http://dev.mysql.com/downloads/connector/j/下載mysql-connector-java-5.1.34-bin.jar包放到：

D:\ActiveMQ\apache-activemq\lib目錄下。

打開並修改配置文件：

 

<beans
  xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
  http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/activemq-core.xsd">

    <!-- Allows us to use system properties as variables in this configuration file -->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <value>file:${activemq.conf}/credentials.properties</value>
        </property>
    </bean>

   <!-- Allows accessing the server log -->
    <bean id="logQuery" class="org.fusesource.insight.log.log4j.Log4jLogQuery"
          lazy-init="false" scope="singleton"
          init-method="start" destroy-method="stop">
    </bean>

    <!--
        The <broker> element is used to configure the ActiveMQ broker.
    -->
    <broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}">

        <destinationPolicy>
            <policyMap>
              <policyEntries>
                <policyEntry topic=">" >
                    <!-- 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>


        <!--
            The managementContext is used to configure how ActiveMQ is exposed in
            JMX. By default, ActiveMQ uses the MBean server that is started by
            the JVM. For more information, see:

            http://activemq.apache.org/jmx.html
        -->
        <managementContext>
            <managementContext createConnector="false"/>
        </managementContext>

        <!--
            Configure message persistence for the broker. The default persistence
            mechanism is the KahaDB store (identified by the kahaDB tag).
            For more information, see:

            http://activemq.apache.org/persistence.html
            <kahaDB directory="${activemq.data}/kahadb"/>
        -->
        <persistenceAdapter>
            <jdbcPersistenceAdapter dataDirectory="${activemq.base}/data" dataSource="#derby-ds"/>
        </persistenceAdapter>


          <!--
            The systemUsage controls the maximum amount of space the broker will
            use before disabling caching and/or slowing down producers. For more information, see:
            http://activemq.apache.org/producer-flow-control.html
          -->
          <systemUsage>
            <systemUsage>
                <memoryUsage>
                    <memoryUsage percentOfJvmHeap="70" />
                </memoryUsage>
                <storeUsage>
                    <storeUsage limit="100 gb"/>
                </storeUsage>
                <tempUsage>
                    <tempUsage limit="50 gb"/>
                </tempUsage>
            </systemUsage>
        </systemUsage>

        <!--
            The transport connectors expose ActiveMQ over a given protocol to
            clients and other brokers. For more information, see:

            http://activemq.apache.org/configuring-transports.html
        -->
        <transportConnectors>
            <!-- DOS protection, limit concurrent connections to 1000 and frame size to 100MB -->
            <transportConnector name="openwire" uri="tcp://0.0.0.0:61616?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
            <transportConnector name="amqp" uri="amqp://0.0.0.0:5672?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
            <transportConnector name="stomp" uri="stomp://0.0.0.0:61613?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
            <transportConnector name="mqtt" uri="mqtt://0.0.0.0:1883?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
            <transportConnector name="ws" uri="ws://0.0.0.0:61614?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
        </transportConnectors>

        <!-- destroy the spring context on shutdown to stop jetty -->
        <shutdownHooks>
            <bean xmlns="http://www.springframework.org/schema/beans" class="org.apache.activemq.hooks.SpringContextHook" />
        </shutdownHooks>

    </broker>
  <bean id="derby-ds" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost/activemq?relaxAutoCommit=true"/>
    <property name="username" value="root"/>
    <property name="password" value=""/>
    <property name="maxActive" value="200"/>
    <property name="poolPreparedStatements" value="true"/>
  </bean>
    <!--
        Enable web consoles, REST and Ajax APIs and demos
        The web consoles requires by default login, you can disable this in the jetty.xml file

        Take a look at ${ACTIVEMQ_HOME}/conf/jetty.xml for more details
    -->
    <import resource="jetty.xml"/>

</beans>
<!-- END SNIPPET: example -->

重啟ActiveMQ打開phpmyadmin發現多了3張表：

然后啟動生產者（不啟動消費者）

在Mysql中可以找到這條消息：

關掉ActiveMQ並重啟，模擬宕機。

然后啟動消費者：

然后發現Mysql中已經沒有這條消息了。