101 lines
5.6 KiB
XML
101 lines
5.6 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!-- ============================================================================= -->
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<!-- Licensed to the Apache Software Foundation (ASF) under one or more -->
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<!-- contributor license agreements. See the NOTICE file distributed with -->
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<!-- this work for additional information regarding copyright ownership. -->
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<!-- The ASF licenses this file to You under the Apache License, Version 2.0 -->
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<!-- (the "License"); you may not use this file except in compliance with -->
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<!-- the License. You may obtain a copy of the License at -->
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<!-- -->
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<!-- http://www.apache.org/licenses/LICENSE-2.0 -->
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<!-- -->
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<!-- Unless required by applicable law or agreed to in writing, software -->
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<!-- distributed under the License is distributed on an "AS IS" BASIS, -->
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<!-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -->
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<!-- See the License for the specific language governing permissions and -->
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<!-- limitations under the License. -->
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<!-- ============================================================================= -->
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % BOOK_ENTITIES SYSTEM "ActiveMQ_User_Manual.ent">
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%BOOK_ENTITIES;
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]>
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<chapter id="message-expiry">
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<title>Message Expiry</title>
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<para>Messages can be set with an optional <emphasis>time to live</emphasis> when sending
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them.</para>
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<para>ActiveMQ will not deliver a message to a consumer after it's time to live has been exceeded.
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If the message hasn't been delivered by the time that time to live is reached the server can
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discard it.</para>
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<para>ActiveMQ's addresses can be assigned a expiry address so that, when messages are expired,
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they are removed from the queue and sent to the expiry address. Many different queues can be
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bound to an expiry address. These <emphasis>expired</emphasis> messages can later be consumed
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for further inspection.</para>
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<section>
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<title>Message Expiry</title>
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<para>Using ActiveMQ Core API, you can set an expiration time directly on the message:</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);</programlisting>
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<para>JMS MessageProducer allows to set a TimeToLive for the messages it sent:</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);</programlisting>
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<para>Expired messages which are consumed from an expiry address have the following
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properties:</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>a String property containing the <emphasis>original address</emphasis> of the
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expired message </para>
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</listitem>
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<listitem>
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<para><literal>_HQ_ORIG_QUEUE</literal></para>
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<para>a String property containing the <emphasis>original queue</emphasis> of the
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expired message </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>a Long property containing the <emphasis>actual expiration time</emphasis> of the
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expired message</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>Configuring Expiry Addresses</title>
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<para>Expiry address are defined in the address-setting configuration:</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></programlisting>
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<para>If messages are expired and no expiry address is specified, messages are simply removed
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from the queue and dropped. Address wildcards can be used to configure expiry address for a
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set of addresses (see <xref linkend="wildcard-syntax"/>).</para>
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</section>
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<section id="configuring.expiry.reaper">
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<title>Configuring The Expiry Reaper Thread</title>
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<para>A reaper thread will periodically inspect the queues to check if messages have
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expired.</para>
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<para>The reaper thread can be configured with the following properties in <literal
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>activemq-configuration.xml</literal></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>How often the queues will be scanned to detect expired messages (in milliseconds,
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default is 30000ms, set to <literal>-1</literal> to disable the reaper thread)</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>The reaper thread priority (it must be between 0 and 9, 9 being the highest
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priority, default is 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>Example</title>
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<para>See <xref linkend="examples.expiry"/> for an example which shows how message expiry is
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configured and used with JMS.</para>
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</section>
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</chapter>
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