82 lines
4.9 KiB
XML
82 lines
4.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!-- ============================================================================= -->
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<!-- Copyright © 2009 Red Hat, Inc. and others. -->
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<!-- -->
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<!-- The text of and illustrations in this document are licensed by Red Hat under -->
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<!-- a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). -->
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<!-- -->
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<!-- An explanation of CC-BY-SA is available at -->
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<!-- -->
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<!-- http://creativecommons.org/licenses/by-sa/3.0/. -->
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<!-- -->
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<!-- In accordance with CC-BY-SA, if you distribute this document or an adaptation -->
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<!-- of it, you must provide the URL for the original version. -->
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<!-- -->
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<!-- Red Hat, as the licensor of this document, waives the right to enforce, -->
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<!-- and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent -->
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<!-- permitted by applicable law. -->
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<!-- ============================================================================= -->
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<chapter id="message-expiry">
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<title>过期的消息</title>
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<para>消息在发送时有一个可选的<emphasis>生存时间</emphasis>属性。</para>
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<para>如果一个消息已经超过了它的生存时间，HornetQ不再将它传递给任何接收者。
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服务器会将过期的消息抛弃。</para>
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<para>HornetQ的地址可以配置一个过期地址，当消息过期时，它们被从队列中删除并被转移到过期地址中。
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多个不同的队列可以绑定到一个过期地址上。这些过期的消息过后可以接收下来以供分析用。</para>
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<section>
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<title>过期消息的配置</title>
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<para>如果使用HornetQ核心API，可以直接在消息上设置过期时间：</para>
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<programlisting>
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// message will expire in 5000ms from now
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message.setExpiration(System.currentTimeMillis() + 5000);
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</programlisting>
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<para>JMS的MessageProducer可以设置一个TimeToLive来控制其发送的消息：</para>
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<programlisting>
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// messages sent by this producer will be retained for 5s (5000ms) before expiration
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producer.setTimeToLive(5000);
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</programlisting>
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<para>从过期地址中接收下来的消息有以下属性：</para>
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<itemizedlist>
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<listitem>
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<para><literal>_HQ_ORIG_ADDRESS</literal></para>
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<para>这是一个字符串，它是该消息的<emphasis>原始地址</emphasis>。</para>
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</listitem>
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<listitem>
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<para><literal>_HQ_ACTUAL_EXPIRY</literal></para>
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<para>一个长整型量，代表此消息<emphasis>实际过期时间</emphasis>。</para>
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</listitem>
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</itemizedlist>
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</section>
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<section id="message-expiry.configuring">
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<title>配置过期地址</title>
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<para>过期地址配置在地址设置（address-setting）中：</para>
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<programlisting>
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<!-- expired messages in exampleQueue will be sent to the expiry address expiryQueue -->
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<address-setting match="jms.queue.exampleQueue">
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<expiry-address>jms.queue.expiryQueue</expiry-address>
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</address-setting>
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</programlisting>
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<para>如果没有定义过期地址，当一个消息过期时，它将被删除。配置过期地址时可以使用通配符
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来给一组地址配置过期地址。（参见<xref linkend="wildcard-syntax"/>）。</para>
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</section>
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<section id="configuring.expiry.reaper">
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<title>配置过期回收线程</title>
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<para>HornetQ有一个回收线程定期地检查队列中的消息，目的是发现是否有消息过期。</para>
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<para>在<literal>hornetq-configuration.xml</literal>文件中可以对回收线程进行配置，参数如下：</para>
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<itemizedlist>
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<listitem>
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<para><literal>message-expiry-scan-period</literal></para>
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<para>过期消息的扫描间隔（单位毫秒，默认为30000ms）。如要关闭扫描，将其设为<literal>-1</literal>。</para>
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</listitem>
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<listitem>
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<para><literal>message-expiry-thread-priority</literal></para>
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<para>回收线程的优先级（为0到9的整数，9优先级最高。默认是3）。</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>例子</title>
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<para>参见<xref linkend="examples.expiry"/>。这个例子展示了在JMS中如何配置使用消息过期功能。</para>
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</section>
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</chapter>
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