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From build...@apache.org
Subject svn commit: r1020038 - in /websites/production/activemq/content: cache/main.pageCache per-destination-policies.html virtual-destinations.html
Date Wed, 25 Oct 2017 16:24:29 GMT
Author: buildbot
Date: Wed Oct 25 16:24:29 2017
New Revision: 1020038

Log:
Production update by buildbot for activemq

Modified:
    websites/production/activemq/content/cache/main.pageCache
    websites/production/activemq/content/per-destination-policies.html
    websites/production/activemq/content/virtual-destinations.html

Modified: websites/production/activemq/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.

Modified: websites/production/activemq/content/per-destination-policies.html
==============================================================================
--- websites/production/activemq/content/per-destination-policies.html (original)
+++ websites/production/activemq/content/per-destination-policies.html Wed Oct 25 16:24:29 2017
@@ -71,7 +71,7 @@
   <tbody>
         <tr>
         <td valign="top" width="100%">
-<div class="wiki-content maincontent"><p>We support a number of different policies which can be attached to individual destinations (queues, topics) or to wildcards of queue/topic hierarchies. This makes it easy to configure how different regions of the JMS destination space are handled.</p><p>The properties you can set on a Destination are as follows:</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Common Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForConsumed</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a message is consumed by a client.</p></td></tr><tr><td colspan="1" rowspan="1" class="c
 onfluenceTd"><p><code>advisoryForDelivery</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a message is sent to a client.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForFastProducers</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message if a producer is deemed fast.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForSlowConsumers</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message if a consumer is deemed slow.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryWhenFull</code></p></td><td colspan="1" rowspan="1" class="conf
 luenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a limit (memory, store, temp disk) is full.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>enableAudit</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When&#160;<strong><code>true</code></strong> the broker will track duplicate messages. Duplicates can happen for non-persistent messages during failover.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>gcInactiveDestinations</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Garbage collect inactive destinations.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>inactiveTimoutBeforeGC</code></p></td><td colspan="1" rowspan="1" class="confluenceTd">
 <p><code>5000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The timeout (in ms) after which a destination is considered inactive.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>includeBodyForAdvisory</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Includes the body of the original message that triggered the advisory as part of the&#160;<strong><code>dataStructure</code></strong> field in the advisory message (where applicable). Normally the message body is cleared.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>maxBrowsePageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>400</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in from the store at one time for a browser.</p></td></tr><tr><td colspan="1" rowspan="1" class="conflue
 nceTd"><p><code>maxDestinations</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>-1</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>(v5.12) If&#160;<strong><code>0</code></strong> or greater, sets the maximum number of destinations that can be created. This parameter is intended to limit the number of hierarchical destinations that can be created under a wildcard destination.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>maxPageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>200</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in from the store at one time. Increase this value to improve performance for queue destination's that contain grouped messages that are consumed by multiple concurrent consumers.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>memoryLimit</code></p></td><td colspan="1" rowspan
 ="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The memory limit (in bytes) of the destination's cursor.</p><p>This memory limit is subordinate to the system level memory limit, as specified by the&#160;<a shape="rect" href="producer-flow-control.html"><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></a> <span class="confluence-link">attribute</span>. There is no default for this value; it simply acts as a child to the overall broker memory until the broker memory is exhausted.</p><p><strong>Note</strong>: when this limit is specified the destination's&#160;<strong><code>cursorMemoryHighWaterMark</code></strong> will be applied against it and not the&#160;<strong><code>&lt;systemUsage&gt;/&gt;&lt;memoryUsage&gt;</code></strong> memory limit.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>minimumMessageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>1024</code></p><
 /td><td colspan="1" rowspan="1" class="confluenceTd"><p>For non-serialized messages (embedded broker) - the assumed size of the message used for memory usage calculation. Serialized messages use the serialized size as the basis for the memory calculation.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>prioritizedMessages</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Persist message priority information.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>producerFlowControl</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If <strong><code>true</code></strong> the broker will throttle (flow-control) the producer. Throttling is achieved either by withholding the producer's ACK or by raising a&#160;<strong><code>javax.jms.ResourceAllocationExc
 eption</code></strong> (that's propagated back to the client) when local resources e.g., memory and/or storage, have been exhausted.</p><p>If&#160;<strong><code>false</code></strong> excess messages will be written to the message store to prevent memory exhaustion. However, when the message store reaches capacity the producer will be throttled until resources are freed.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>slowConsumerStrategy</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the strategy for handling slow consumers. See <a shape="rect" class="external-link" href="https://github.com/apache/activemq/blob/master/activemq-broker/src/main/java/org/apache/activemq/broker/region/policy/AbortSlowConsumerStrategy.java" rel="nofollow">AbortSlowConsumerStrategy.</a></p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>storeUsageHighWat
 erMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>100</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold of the&#160;<strong><code>&lt;systemUsage&gt;/&lt;storeUsage&gt;</code></strong> store limit which when exceeded causes a send to block.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>useCache</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If&#160;<strong><code>true</code></strong> persistent messages are cached for fast retrieval from store.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span><code>usePrefetchExtension</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The prefetch extension is used when a&#160;message is delivered but not ACK
 'ed, such that the broker can dispatch&#160;another message, e.g., <code>prefetch == 0</code>, the idea being that there will always be prefetch number of messages pending. It also allows a transaction batch to exceed the prefetch&#160;value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">sendFailIfNoSpace </span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">false</span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><span style="color: rgb(0,0,0);">(v5.16.0) If true, will cause a send to fail with a javax.jms.ResourceAllocationException when the destination has reached is resource limits (memory or storage)</span></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">sendFailIfNoSpaceAfterTimeout</span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><code>0</code></td><td colspan="1" rowspan="1" clas
 s="confluenceTd"><span style="color: rgb(0,0,0);">(v5.16.0) if &gt; 0, will cause a send to fail with a javax.jms.ResourceAllocationException when the destination resource limits (memory or storage) remain exhausted for the configured duration in milliseconds</span></td></tr></tbody></table></div><p>Additional properties for a Queue</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Queue Only Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>allConsumersExclusiveByDefault</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When&#160;<strong><code>true</code></strong> all consumers will be exclusive. See <a shape="rect" href="nms/activemq-exclus
 ive-consumers.html">ActiveMQ Exclusive Consumers</a></p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>cursorMemoryHighWaterMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>70</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold applied either to the&#160;<strong><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></strong> or the destination's&#160;<strong><code>memoryLimit</code></strong> (when defined) which when exceeded will cause the destination's cursor to either block or write to disk.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>consumersBeforeDispatchStarts</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When the first consumer connects, wait for specified number of consumers before message dispatching starts.</p></td></tr><tr><td colspan="1" rowspan="1" c
 lass="confluenceTd"><p><code>expireMessagesPeriod</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The period (in ms) of checks for message expiry on queued messages, value of 0 disables.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>lazyDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Only page in from store the number of messages that can be dispatched at time.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><pre>maxExpirePageSize</pre></td><td colspan="1" rowspan="1" class="confluenceTd"><pre>400</pre></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in when periodically expiring messages.</p><p>Messages are paged in according to this setting if the number of messages in memory pending dis
 patch is less than this value, and there are messages in the store to page in. Messages are expired during this paging step as they are brought into memory from the store.</p><p>Once the paging process is completed, messages are expired from the list of those that are in memory and pending dispatch, then from the list of those that are in memory but not yet targeted at a subscription.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>optimizedDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Don't use a separate thread for dispatching from a Queue.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>persistJMSRedelivered</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>(v 5.10) If true, before a persistent message is dispatched by the br
 oker for the first time, the message is rewritten to reflect the possible delivery.</p><p>This ensures the message&#160;<strong><code>JMSRedelivered</code></strong> header is a reliable indication of possible duplicate delivery.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>queuePrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for consumers that are using the default value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>strictOrderDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If&#160;<strong><code>true</code></strong> queue will not round robin consumers, but it'll use a single one until its prefetch buffer is full.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>timeBefore
 DispatchStarts</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When the first consumer connects, wait for specified time (in ms) before message dispatching starts.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>useConsumerPriority</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Use the priority of a consumer when dispatching messages from a Queue.</p></td></tr></tbody></table></div><p>Additional properties for a Topic</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Topic Only Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p>
 <code>advisoryForDiscardingMessages</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory when a message is discarded from a non durable subscription.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>cursorMemoryHighWaterMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>70</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold applied to the&#160;<strong><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></strong> which when exceeded will cause the destination's cursor to either block or write to disk.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span style="color: rgb(0,0,0);"><code>alwaysRetroactive</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confl
 uenceTd"><p>Makes all subscribers retroactive negating the need to modify the clients to enable this feature.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>durableTopicPrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for durable topic consumers that are using the default value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span style="color: rgb(0,0,0);"><code>expireMessagesPeriod</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The interval (in ms) between message expiration checks on inactive durable subscribers.</p><p><strong>Note</strong>: set to <strong><code>0</code></strong> to disable message expiration checking.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><co
 de>topicPrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for topic consumers that are using the default value.</p></td></tr></tbody></table></div><p><span style="line-height: 1.4285715;">The following are examples of different policies that can be customized on a per destination basis:</span></p><ul><li><a shape="rect" href="dispatch-policies.html">Dispatch Policies</a></li></ul><p>&#160;</p></div>
+<div class="wiki-content maincontent"><p>We support a number of different policies which can be attached to individual destinations (queues, topics) or to wildcards of queue/topic hierarchies. This makes it easy to configure how different regions of the JMS destination space are handled.</p><p>The properties you can set on a Destination are as follows:</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Common Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForConsumed</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a message is consumed by a client.</p></td></tr><tr><td colspan="1" rowspan="1" class="c
 onfluenceTd"><p><code>advisoryForDelivery</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a message is sent to a client.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForFastProducers</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message if a producer is deemed fast.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryForSlowConsumers</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message if a consumer is deemed slow.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>advisoryWhenFull</code></p></td><td colspan="1" rowspan="1" class="conf
 luenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory message when a limit (memory, store, temp disk) is full.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>enableAudit</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When&#160;<strong><code>true</code></strong> the broker will track duplicate messages. Duplicates can happen for non-persistent messages during failover.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>gcInactiveDestinations</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Garbage collect inactive destinations.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>inactiveTimoutBeforeGC</code></p></td><td colspan="1" rowspan="1" class="confluenceTd">
 <p><code>5000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The timeout (in ms) after which a destination is considered inactive.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>includeBodyForAdvisory</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Includes the body of the original message that triggered the advisory as part of the&#160;<strong><code>dataStructure</code></strong> field in the advisory message (where applicable). Normally the message body is cleared.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>maxBrowsePageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>400</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in from the store at one time for a browser.</p></td></tr><tr><td colspan="1" rowspan="1" class="conflue
 nceTd"><p><code>maxDestinations</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>-1</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>(v5.12) If&#160;<strong><code>0</code></strong> or greater, sets the maximum number of destinations that can be created. This parameter is intended to limit the number of hierarchical destinations that can be created under a wildcard destination.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>maxPageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>200</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in from the store at one time. Increase this value to improve performance for queue destination's that contain grouped messages that are consumed by multiple concurrent consumers.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>memoryLimit</code></p></td><td colspan="1" rowspan
 ="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The memory limit (in bytes) of the destination's cursor.</p><p>This memory limit is subordinate to the system level memory limit, as specified by the&#160;<a shape="rect" href="producer-flow-control.html"><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></a> <span class="confluence-link">attribute</span>. There is no default for this value; it simply acts as a child to the overall broker memory until the broker memory is exhausted.</p><p><strong>Note</strong>: when this limit is specified the destination's&#160;<strong><code>cursorMemoryHighWaterMark</code></strong> will be applied against it and not the&#160;<strong><code>&lt;systemUsage&gt;/&gt;&lt;memoryUsage&gt;</code></strong> memory limit.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>minimumMessageSize</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>1024</code></p><
 /td><td colspan="1" rowspan="1" class="confluenceTd"><p>For non-serialized messages (embedded broker) - the assumed size of the message used for memory usage calculation. Serialized messages use the serialized size as the basis for the memory calculation.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>prioritizedMessages</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Persist message priority information.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>producerFlowControl</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If <strong><code>true</code></strong> the broker will throttle (flow-control) the producer. Throttling is achieved either by withholding the producer's ACK or by raising a&#160;<strong><code>javax.jms.ResourceAllocationExc
 eption</code></strong> (that's propagated back to the client) when local resources e.g., memory and/or storage, have been exhausted.</p><p>If&#160;<strong><code>false</code></strong> excess messages will be written to the message store to prevent memory exhaustion. However, when the message store reaches capacity the producer will be throttled until resources are freed.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>slowConsumerStrategy</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the strategy for handling slow consumers. See <a shape="rect" class="external-link" href="https://github.com/apache/activemq/blob/master/activemq-broker/src/main/java/org/apache/activemq/broker/region/policy/AbortSlowConsumerStrategy.java" rel="nofollow">AbortSlowConsumerStrategy.</a></p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>storeUsageHighWat
 erMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>100</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold of the&#160;<strong><code>&lt;systemUsage&gt;/&lt;storeUsage&gt;</code></strong> store limit which when exceeded causes a send to block.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>useCache</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If&#160;<strong><code>true</code></strong> persistent messages are cached for fast retrieval from store.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span><code>usePrefetchExtension</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The prefetch extension is used when a&#160;message is delivered but not ACK
 'ed, such that the broker can dispatch&#160;another message, e.g., <code>prefetch == 0</code>, the idea being that there will always be prefetch number of messages pending. It also allows a transaction batch to exceed the prefetch&#160;value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">sendFailIfNoSpace </span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">false</span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><span style="color: rgb(0,0,0);">(v5.16.0) If true, will cause a send to fail with a javax.jms.ResourceAllocationException when the destination has reached is resource limits (memory or storage)</span></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><code><span style="color: rgb(0,0,0);">sendFailIfNoSpaceAfterTimeout</span></code></td><td colspan="1" rowspan="1" class="confluenceTd"><code>0</code></td><td colspan="1" rowspan="1" clas
 s="confluenceTd"><span style="color: rgb(0,0,0);">(v5.16.0) if &gt; 0, will cause a send to fail with a javax.jms.ResourceAllocationException when the destination resource limits (memory or storage) remain exhausted for the configured duration in milliseconds</span></td></tr></tbody></table></div><p>Additional properties for a Queue</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Queue Only Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>allConsumersExclusiveByDefault</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When&#160;<strong><code>true</code></strong> all consumers will be exclusive. See <a shape="rect" href="nms/activemq-exclus
 ive-consumers.html">ActiveMQ Exclusive Consumers</a></p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>cursorMemoryHighWaterMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>70</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold applied either to the&#160;<strong><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></strong> or the destination's&#160;<strong><code>memoryLimit</code></strong> (when defined) which when exceeded will cause the destination's cursor to either block or write to disk.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>consumersBeforeDispatchStarts</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When the first consumer connects, wait for specified number of consumers before message dispatching starts.</p></td></tr><tr><td colspan="1" rowspan="1" c
 lass="confluenceTd"><p><code>expireMessagesPeriod</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The period (in ms) of checks for message expiry on queued messages, value of 0 disables.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>lazyDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Only page in from store the number of messages that can be dispatched at time.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><pre>maxExpirePageSize</pre></td><td colspan="1" rowspan="1" class="confluenceTd"><pre>400</pre></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of messages to page in when periodically expiring messages.</p><p>Messages are paged in according to this setting if the number of messages in memory pending dis
 patch is less than this value, and there are messages in the store to page in. Messages are expired during this paging step as they are brought into memory from the store.</p><p>Once the paging process is completed, messages are expired from the list of those that are in memory and pending dispatch, then from the list of those that are in memory but not yet targeted at a subscription.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>optimizedDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Don't use a separate thread for dispatching from a Queue.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>persistJMSRedelivered</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>(v 5.10) If true, before a persistent message is dispatched by the br
 oker for the first time, the message is rewritten to reflect the possible delivery.</p><p>This ensures the message&#160;<strong><code>JMSRedelivered</code></strong> header is a reliable indication of possible duplicate delivery.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>queuePrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for consumers that are using the default value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>strictOrderDispatch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>If&#160;<strong><code>true</code></strong> queue will not round robin consumers, but it'll use a single one until its prefetch buffer is full.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>timeBefore
 DispatchStarts</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>When the first consumer connects, wait for specified time (in ms) before message dispatching starts.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>useConsumerPriority</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Use the priority of a consumer when dispatching messages from a Queue.</p></td></tr></tbody></table></div><p>Additional properties for a Topic</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>Topic Only Property</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Default Value</p></th><th colspan="1" rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p>
 <code>advisoryForDiscardingMessages</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Send an advisory when a message is discarded from a non durable subscription.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>cursorMemoryHighWaterMark</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>70</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The percentage (%) threshold applied to the&#160;<strong><code>&lt;systemUsage&gt;/&lt;memoryUsage&gt;</code></strong> which when exceeded will cause the destination's cursor to either block or write to disk.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span style="color: rgb(0,0,0);"><code>alwaysRetroactive</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1" class="confl
 uenceTd"><p>Makes all subscribers retroactive negating the need to modify the clients to enable this feature.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>durableTopicPrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for durable topic consumers that are using the default value.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><span style="color: rgb(0,0,0);"><code>expireMessagesPeriod</code><br clear="none"></span></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>The interval (in ms) between message expiration checks on inactive durable subscribers.</p><p><strong>Note</strong>: set to <strong><code>0</code></strong> to disable message expiration checking.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><co
 de>topicPrefetch</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><code>n/a</code></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p>Sets the prefetch for topic consumers that are using the default value.</p></td></tr></tbody></table></div><p><span style="line-height: 1.4285715;">The following are examples of different policies that can be customized on a per destination basis:</span></p><ul><li><a shape="rect" href="dispatch-policies.html">Dispatch Policies</a></li></ul><pre>&#160;</pre><p>An example from the demos&#160;<a shape="rect" class="external-link" href="https://git-wip-us.apache.org/repos/asf?p=activemq.git;a=blob;f=assembly/src/release/examples/conf/activemq-demo.xml;hb=HEAD">https://git-wip-us.apache.org/repos/asf?p=activemq.git;a=blob;f=assembly/src/release/examples/conf/activemq-demo.xml;hb=HEAD</a>:&#160;</p><p><code class="xml plain">&lt;</code><code class="xml keyword">beans</code> <code class="xml color1">xmlns</code><code class="xml pl
 ain">=</code><code class="xml string">"<a shape="rect" class="external-link" href="http://www.springframework.org/schema/beans" rel="nofollow">http://www.springframework.org/schema/beans</a>"</code></p><div class="line number2 index1 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml color1">xmlns:amq</code><code class="xml plain">=</code><code class="xml string">"<a shape="rect" class="external-link" href="http://activemq.apache.org/schema/core">http://activemq.apache.org/schema/core</a>"</code></div><div class="line number3 index2 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml color1">xmlns:xsi</code><code class="xml plain">=</code><code class="xml string">"<a shape="rect" class="external-link" href="http://www.w3.org/2001/XMLSchema-instance" rel="nofollow">http://www.w3.org/2001/XMLSchema-instance</a>"</code></div><div class="line number4 index3 alt1"><code class="xml spaces">&#160;&#1
 60;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">xsi:schemaLocation="<a shape="rect" class="external-link" href="http://www.springframework.org/schema/beans" rel="nofollow">http://www.springframework.org/schema/beans</a> <a shape="rect" class="external-link" href="http://www.springframework.org/schema/beans/spring-beans-2.0.xsd" rel="nofollow">http://www.springframework.org/schema/beans/spring-beans-2.0.xsd</a></code></div><div class="line number5 index4 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain"><a shape="rect" class="external-link" href="http://activemq.apache.org/schema/core">http://activemq.apache.org/schema/core</a> <a shape="rect" class="external-link" href="http://activemq.apache.org/schema/core/activemq-core.xsd">http://activemq.apache.org/schema/core/activemq-core.xsd</a>"&gt;</cod
 e></div><div class="line number6 index5 alt1">&#160;</div><div class="line number7 index6 alt2"><code class="xml spaces">&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">bean</code> <code class="xml color1">class</code><code class="xml plain">=</code><code class="xml string">"org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"</code><code class="xml plain">/&gt;</code></div><div class="line number8 index7 alt1">&#160;</div><div class="line number9 index8 alt2"><code class="xml spaces">&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">broker</code> <code class="xml color1">persistent</code><code class="xml plain">=</code><code class="xml string">"false"</code> <code class="xml color1">brokerName</code><code class="xml plain">=</code><code class="xml string">"${brokername}"</code> <code class="xml color1">xmlns</code><code class="xml plain">=</code><code class="xml string">"<a shape="rect" class="external
 -link" href="http://activemq.apache.org/schema/core">http://activemq.apache.org/schema/core</a>"</code><code class="xml plain">&gt;</code></div><div class="line number10 index9 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;</code><code class="xml comments">&lt;!--&#160; lets define the dispatch policy --&gt;</code></div><div class="line number11 index10 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">destinationPolicy</code><code class="xml plain">&gt;</code></div><div class="line number12 index11 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyMap</code><code class="xml plain">&gt;</code></div><div class="line number13 index12 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntries</code><code class="xml 
 plain">&gt;</code></div><div class="line number14 index13 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntry</code> <code class="xml plain">topic="FOO.&gt;"&gt;</code></div><div class="line number15 index14 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">dispatchPolicy</code><code class="xml plain">&gt;</code></div><div class="line number16 index15 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">roundRobinDispatchPolicy</code> <code class="xml plain">/&gt;</code></div><div class="line number17 index16 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><c
 ode class="xml plain">&lt;/</code><code class="xml keyword">dispatchPolicy</code><code class="xml plain">&gt;</code></div><div class="line number18 index17 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">subscriptionRecoveryPolicy</code><code class="xml plain">&gt;</code></div><div class="line number19 index18 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">lastImageSubscriptionRecoveryPolicy</code> <code class="xml plain">/&gt;</code></div><div class="line number20 index19 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">subscriptionRecoveryPolicy</code><code class="xml plain">&gt;</code></div><div class="li
 ne number21 index20 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">policyEntry</code><code class="xml plain">&gt;</code></div><div class="line number22 index21 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code>&#160;</div><div class="line number23 index22 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntry</code> <code class="xml plain">topic="ORDERS.&gt;"&gt;</code></div><div class="line number24 index23 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">dispatchPolicy</code><code class="xml plain">&gt;</code></div><div class="line number25 index24 alt2"><code class="xml spaces">&#160;&#16
 0;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">strictOrderDispatchPolicy</code> <code class="xml plain">/&gt;</code></div><div class="line number26 index25 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">dispatchPolicy</code><code class="xml plain">&gt;</code></div><div class="line number27 index26 alt2">&#160;</div><div class="line number28 index27 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml comments">&lt;!--&#160; 1 minute's worth --&gt;</code></div><div class="line number29 index28 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">subscriptionRecoveryPolicy</code><
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 ass="line number33 index32 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;</code>&#160;</div><div class="line number34 index33 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntry</code> <code class="xml plain">topic="PRICES.&gt;"&gt;</code></div><div class="line number35 index34 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml comments">&lt;!-- lets force old messages to be discarded for slow consumers --&gt;</code></div><div class="line number36 index35 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">pendingMessageLimitStrategy</code><code class="xml plain">&gt;</code></div><div class="line number37 index36 alt2"><code class="xml spaces">&#160;&#160;&#160;&#16
 0;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">constantPendingMessageLimitStrategy</code> <code class="xml color1">limit</code><code class="xml plain">=</code><code class="xml string">"10"</code><code class="xml plain">/&gt;</code></div><div class="line number38 index37 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">pendingMessageLimitStrategy</code><code class="xml plain">&gt;</code></div><div class="line number39 index38 alt2">&#160;</div><div class="line number40 index39 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml comments">&lt;!--&#160; 10 seconds worth --&gt;</code></div><div class="line number41 index40 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#16
 0;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">subscriptionRecoveryPolicy</code><code class="xml plain">&gt;</code></div><div class="line number42 index41 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">timedSubscriptionRecoveryPolicy</code> <code class="xml color1">recoverDuration</code><code class="xml plain">=</code><code class="xml string">"10000"</code> <code class="xml plain">/&gt;</code></div><div class="line number43 index42 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">subscriptionRecoveryPolicy</code><code class="xml plain">&gt;</code></div><div class="line number44 index43 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code>
 &#160;</div><div class="line number45 index44 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">policyEntry</code><code class="xml plain">&gt;</code></div><div class="line number46 index45 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntry</code> <code class="xml color1">tempTopic</code><code class="xml plain">=</code><code class="xml string">"true"</code> <code class="xml color1">advisoryForConsumed</code><code class="xml plain">=</code><code class="xml string">"true"</code> <code class="xml plain">/&gt;</code></div><div class="line number47 index46 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;</code><code class="xml keyword">policyEntry</code> <code class="xml color1">tempQue
 ue</code><code class="xml plain">=</code><code class="xml string">"true"</code> <code class="xml color1">advisoryForConsumed</code><code class="xml plain">=</code><code class="xml string">"true"</code> <code class="xml plain">/&gt;</code></div><div class="line number48 index47 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">policyEntries</code><code class="xml plain">&gt;</code></div><div class="line number49 index48 alt2"><code class="xml spaces">&#160;&#160;&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">policyMap</code><code class="xml plain">&gt;</code></div><div class="line number50 index49 alt1"><code class="xml spaces">&#160;&#160;&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">destinationPolicy</code><code class="xml plain">&gt;</code></div><div class="line number51 index50 alt2"><code class="xml spa
 ces">&#160;&#160;</code><code class="xml plain">&lt;/</code><code class="xml keyword">broker</code><code class="xml plain">&gt;</code></div><div class="line number52 index51 alt1"><code class="xml plain">&lt;/</code><code class="xml keyword">beans</code><code class="xml plain">&gt;</code></div></div>
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Modified: websites/production/activemq/content/virtual-destinations.html
==============================================================================
--- websites/production/activemq/content/virtual-destinations.html (original)
+++ websites/production/activemq/content/virtual-destinations.html Wed Oct 25 16:24:29 2017
@@ -71,46 +71,7 @@
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-<div class="wiki-content maincontent"><p><em>Virtual Destinations</em> allow us to create logical destinations that clients can use to produce and consume from but which map onto one or more <em>physical destinations</em>. It allows us to provide more flexible loosely coupled messaging configurations.</p><h2 id="VirtualDestinations-VirtualTopics">Virtual Topics</h2><p>The idea behind <em>publish subscribe</em> is a great one. Allow producers to be decoupled from consumers so that they do not even know how many consumers are interested in the messages they publish. The JMS specification defines support for durable topics however they have limitations as we will describe...</p><h3 id="VirtualDestinations-ThelimitationsofJMSdurabletopics">The limitations of JMS durable topics</h3><p>A JMS durable subscriber MessageConsumer is created with a unique JMS clientID and durable subscriber name. To be JMS compliant only one JMS connection can be active at any point in time for one JMS clientI
 D, and only one consumer can be active for a clientID and subscriber name. i.e., only <strong>one</strong> thread can be actively consuming from a given logical topic subscriber. This means we cannot implement</p><ul><li>load balancing of messages.</li><li>fast failover of the subscriber if that one process running that one consumer thread dies.</li></ul><p>Now <em>queue</em> semantics in JMS offer the ability to load balance work across a number of consumers in a reliable way - allowing many threads, processes and machines to be used to process messages. Then we have sophisticated sticky load balancing techniques like <a shape="rect" href="message-groups.html">Message Groups</a> to load balance and parallelise work while maintaining ordering.</p><p>Another added benefit of having physical queues for each logical topic subscriber is we can them monitor the queue depths via <a shape="rect" href="jmx.html">JMX</a> to monitor system performance together with being able to browse these 
 physical queues.</p><h3 id="VirtualDestinations-VirtualTopicstotherescue">Virtual Topics to the rescue</h3><p>The idea behind virtual topics is that producers send to a topic in the usual JMS way. Consumers can continue to use the Topic semantics in the JMS specification. However if the topic is virtual, consumer can consume from a physical queue for a logical topic subscription, allowing many consumers to be running on many machines &amp; threads to load balance the load.</p><p>E.g., let's say we have a topic called <strong>VirtualTopic.Orders</strong>. (Where the prefix VirtualTopic. indicates its a virtual topic). And we logically want to send orders to systems A and B. Now with regular durable topics we'd create a JMS consumer for clientID_A and "A" along with clientID_B and "B".</p><p>With virtual topics we can just go right ahead and consume to queue <strong>Consumer.A.VirtualTopic.Orders</strong> to be a consumer for system A or consume to <strong>Consumer.B.VirtualTopic.Orde
 rs</strong> to be a consumer for system B.</p><p>We can now have a pool of consumers for each system which then compete for messages for systems A or B such that all the messages for system A are processed exactly once and similarly for system B.</p><h3 id="VirtualDestinations-Customizingtheout-of-the-boxdefaults">Customizing the out-of-the-box defaults</h3><p>The out-of-the-box defaults are described above. Namely that the only virtual topics available must be within the <strong>VirtualTopic.&gt;</strong> namespace and that the consumer queues are named <strong>Consumer.*.VirtualTopic.&gt;</strong>.</p><p>You can configure this to use whatever naming convention you wish. The following <a shape="rect" class="external-link" href="https://svn.apache.org/repos/asf/incubator/activemq/trunk/activemq-unit-tests/src/test/resources/org/apache/activemq/broker/virtual/global-virtual-topics.xml">example</a> shows how to make all topics virtual topics. The example below is using the name <stron
 g>&gt;</strong> to indicate 'match all topics'. You could use this wildcard to apply different virtual topic policies in different hierarchies.</p><parameter ac:name="">xml</parameter><plain-text-body>&lt;destinationInterceptors&gt;
-  &lt;virtualDestinationInterceptor&gt;
-	&lt;virtualDestinations&gt;
-	  &lt;virtualTopic name="&gt;" prefix="VirtualTopicConsumers.*." selectorAware="false"/&gt;
-	&lt;/virtualDestinations&gt;
-  &lt;/virtualDestinationInterceptor&gt;
-&lt;/destinationInterceptors&gt;</plain-text-body><p>Note that making a topic virtual does add a small CPU overhead when sending messages to the topic but it is fairly small.</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh">Option</th><th colspan="1" rowspan="1" class="confluenceTh">Default</th><th colspan="1" rowspan="1" class="confluenceTh">Description</th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">selectorAware</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">only messages that match one of the existing subscribers are actually dispatched. Using this option prevents the build up of unmatched messages when selectors are used by exclusive consumers</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">local</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, d
 on't fan out messages that were received over a network</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">concurrentSend</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, use an executor to fanout such that sends occur in parallel. This allows the journal to batch writes which will reduce disk io (5.12)</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">transactedSend</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, use a transaction for fanout sends such that there is a single disk sync. A local broker transaction will be created if there is no client transaction (5.13)</td></tr></tbody></table></div><p>&#160;</p><h2 id="VirtualDestinations-CompositeDestinations">Composite Destinations</h2><p>Composite Destinations allow for one-to-many relationships on individual destinations; the main use case is for <em>composit
 e queues</em>. For example when a message is sent to queue A you may want to forward it also to queues B and C and topic D. Composite destinations are then a mapping from a virtual destination to a collection of other physical destinations. In this case the mapping is broker side and the client is unaware of the mapping between the destinations. This is different from client side <a shape="rect" href="composite-destinations.html">Composite Destinations</a> where the client uses a URL notation to specify the actual physical destinations that a message must be sent to.</p><p>The following <a shape="rect" class="external-link" href="http://svn.apache.org/repos/asf/incubator/activemq/trunk/activemq-unit-tests/src/test/resources/org/apache/activemq/broker/virtual/composite-queue.xml">example</a> shows how to set up a <strong>&lt;compositeQueue/&gt;</strong> element in the XML configuration so that when a message is sent to <code>MY.QUEUE</code> then it is really forwarded to the physical
  queue <code>FOO</code> and the topic <code>BAR</code>.</p><parameter ac:name="">xml</parameter><plain-text-body>&lt;destinationInterceptors&gt;
-  &lt;virtualDestinationInterceptor&gt;
-	&lt;virtualDestinations&gt;
-	  &lt;compositeQueue name="MY.QUEUE"&gt;
-		&lt;forwardTo&gt;
-		  &lt;queue physicalName="FOO" /&gt;
-		  &lt;topic physicalName="BAR" /&gt;
-		&lt;/forwardTo&gt;
-	  &lt;/compositeQueue&gt;
-	&lt;/virtualDestinations&gt;
-  &lt;/virtualDestinationInterceptor&gt;
-&lt;/destinationInterceptors&gt;</plain-text-body><p>By default, subscribers cannot consume messages directly from a composite queue or topic - it is a logical construct only. Given the configuration above, subscribers can only consume messages from <code>FOO</code> and <code>BAR</code>; but not <code>MY.QUEUE</code>.</p><p>This behaviour can be altered to implement use cases such as watching a queue by sending the same messages to a notification topic (wire tapping), by setting the optionally set <code>forwardOnly</code> attribute to false.</p><parameter ac:name="">xml</parameter><plain-text-body>&lt;compositeQueue name="IncomingOrders" forwardOnly="false"&gt;
-    &lt;forwardTo&gt;
-        &lt;topic physicalName="Notifications" /&gt;
-    &lt;/forwardTo&gt;
-&lt;/compositeQueue&gt;</plain-text-body><p>Messages sent to <code>IncomingOrders</code> will all be copied and forwarded to <code>Notifications</code>, before being placed on the physical <code>IncomingOrders</code> queue for consumption by subscribers.</p><p>Where the <code>forwardOnly</code> attribute is not defined or is set to <code>true</code>, there is no logical difference between a <code>compositeQueue</code> and a <code>compositeTopic</code> - they can be used interchangeably. It is only when a composite destination is made physical through the use of <code>forwardOnly</code> that the choice of <code>compositeTopic</code>/<code>compositeQueue</code> has an impact on behavior.</p><h3 id="VirtualDestinations-Usingfiltereddestinations">Using filtered destinations</h3><p>From Apache ActiveMQ <strong>4.2</strong> onwards you can now use selectors to define virtual destinations.</p><p>You may wish to create a virtual destination which forwards messages to multiple destinations b
 ut applying a selector first to decide if the message really does have to go to a particular destination.</p><p>The following example shows how a message sent to the virtual destination <strong>MY.QUEUE</strong> will be forwarded to <strong>FOO</strong> and <strong>BAR</strong> if the selectors match</p><parameter ac:name="">xml</parameter><plain-text-body>&lt;destinationInterceptors&gt;
-  &lt;virtualDestinationInterceptor&gt;
-	&lt;virtualDestinations&gt;
-	  &lt;compositeQueue name="MY.QUEUE"&gt;
-		&lt;forwardTo&gt;
-		  &lt;filteredDestination selector="odd = 'yes'" queue="FOO"/&gt;
-		  &lt;filteredDestination selector="i = 5" topic="BAR"/&gt;
-		&lt;/forwardTo&gt;
-	  &lt;/compositeQueue&gt;
-	&lt;/virtualDestinations&gt;
-  &lt;/virtualDestinationInterceptor&gt;
-&lt;/destinationInterceptors&gt;</plain-text-body><h2 id="VirtualDestinations-AvoidingDuplicateMessageinaNetworkofBrokers">Avoiding Duplicate Message in a Network of Brokers</h2><p>You have to make sure that the messages sent to the <strong>Consumer.*.VirtualTopic.&gt;</strong> destination are not forwarded when you're using both queue-based and non-queue based subscribers to the virtual topic (that is, if you have normal topic subscribers to the virtual topic). If you use Virtual Topics in a network of brokers, it is likely you will get duplicate messages if you use the default network configuration. This is because a network node will not only forward message sent to the virtual topic, but also the associated physical queues. To fix this, you should disable forwarding messages on the associated physical queues.</p><p>Here is an example of how to do that:</p><parameter ac:name="">xml</parameter><plain-text-body>    &lt;networkConnectors&gt;
-      &lt;networkConnector uri="static://(tcp://localhost:61617)"&gt;
-      	&lt;excludedDestinations&gt;
-   	  &lt;queue physicalName="Consumer.*.VirtualTopic.&gt;"/&gt;
-      	&lt;/excludedDestinations&gt;
-      &lt;/networkConnector&gt;
-    &lt;/networkConnectors&gt;
-</plain-text-body></div>
+<div class="wiki-content maincontent"><p><em>Virtual Destinations</em> allow us to create logical destinations that clients can use to produce and consume from but which map onto one or more <em>physical destinations</em>. It allows us to provide more flexible loosely coupled messaging configurations.</p><h2 id="VirtualDestinations-VirtualTopics">Virtual Topics</h2><p>The idea behind <em>publish subscribe</em> is a great one. Allow producers to be decoupled from consumers so that they do not even know how many consumers are interested in the messages they publish. The JMS specification defines support for durable topics however they have limitations as we will describe...</p><h3 id="VirtualDestinations-ThelimitationsofJMSdurabletopics">The limitations of JMS durable topics</h3><p>A JMS durable subscriber MessageConsumer is created with a unique JMS clientID and durable subscriber name. To be JMS compliant only one JMS connection can be active at any point in time for one JMS clientI
 D, and only one consumer can be active for a clientID and subscriber name. i.e., only <strong>one</strong> thread can be actively consuming from a given logical topic subscriber. This means we cannot implement</p><ul><li>load balancing of messages.</li><li>fast failover of the subscriber if that one process running that one consumer thread dies.</li></ul><p>Now <em>queue</em> semantics in JMS offer the ability to load balance work across a number of consumers in a reliable way - allowing many threads, processes and machines to be used to process messages. Then we have sophisticated sticky load balancing techniques like <a shape="rect" href="message-groups.html">Message Groups</a> to load balance and parallelise work while maintaining ordering.</p><p>Another added benefit of having physical queues for each logical topic subscriber is we can them monitor the queue depths via <a shape="rect" href="jmx.html">JMX</a> to monitor system performance together with being able to browse these 
 physical queues.</p><h3 id="VirtualDestinations-VirtualTopicstotherescue">Virtual Topics to the rescue</h3><p>The idea behind virtual topics is that producers send to a topic in the usual JMS way. Consumers can continue to use the Topic semantics in the JMS specification. However if the topic is virtual, consumer can consume from a physical queue for a logical topic subscription, allowing many consumers to be running on many machines &amp; threads to load balance the load.</p><p>E.g., let's say we have a topic called <strong>VirtualTopic.Orders</strong>. (Where the prefix VirtualTopic. indicates its a virtual topic). And we logically want to send orders to systems A and B. Now with regular durable topics we'd create a JMS consumer for clientID_A and "A" along with clientID_B and "B".</p><p>With virtual topics we can just go right ahead and consume to queue <strong>Consumer.A.VirtualTopic.Orders</strong> to be a consumer for system A or consume to <strong>Consumer.B.VirtualTopic.Orde
 rs</strong> to be a consumer for system B.</p><p>We can now have a pool of consumers for each system which then compete for messages for systems A or B such that all the messages for system A are processed exactly once and similarly for system B.</p><h3 id="VirtualDestinations-Customizingtheout-of-the-boxdefaults">Customizing the out-of-the-box defaults</h3><p>The out-of-the-box defaults are described above. Namely that the only virtual topics available must be within the <strong>VirtualTopic.&gt;</strong> namespace and that the consumer queues are named <strong>Consumer.*.VirtualTopic.&gt;</strong>.</p><p>You can configure this to use whatever naming convention you wish. The following <a shape="rect" class="external-link" href="https://svn.apache.org/repos/asf/incubator/activemq/trunk/activemq-unit-tests/src/test/resources/org/apache/activemq/broker/virtual/global-virtual-topics.xml">example</a> shows how to make all topics virtual topics. The example below is using the name <stron
 g>&gt;</strong> to indicate 'match all topics'. You could use this wildcard to apply different virtual topic policies in different hierarchies.</p><pre><span style="color: rgb(0,0,0);">&lt;destinationInterceptors&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;virtualDestinationInterceptor&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;virtualDestinations&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;virtualTopic name="&gt;" prefix="VirtualTopicConsumers.*." selectorAware="false"/&gt; </span>   </pre><pre>   &lt;/virtualDestinations&gt;</pre><pre><span style="color: rgb(0,0,0);"> &lt;/virtualDestinationInterceptor&gt; </span></pre><pre><span style="color: rgb(0,0,0);">&lt;/destinationInterceptors&gt;</span></pre><p>&#160;</p><p>Note that making a topic virtual does add a small CPU overhead when sending messages to the topic but it is fairly small.</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" c
 lass="confluenceTh">Option</th><th colspan="1" rowspan="1" class="confluenceTh">Default</th><th colspan="1" rowspan="1" class="confluenceTh">Description</th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">selectorAware</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">only messages that match one of the existing subscribers are actually dispatched. Using this option prevents the build up of unmatched messages when selectors are used by exclusive consumers</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">local</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, don't fan out messages that were received over a network</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">concurrentSend</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, use an executor t
 o fanout such that sends occur in parallel. This allows the journal to batch writes which will reduce disk io (5.12)</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">transactedSend</td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, use a transaction for fanout sends such that there is a single disk sync. A local broker transaction will be created if there is no client transaction (5.13)</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><span>dropOnResourceLimit</span></td><td colspan="1" rowspan="1" class="confluenceTd">false</td><td colspan="1" rowspan="1" class="confluenceTd">when true, ignore any ResourceAllocationException thrown during fanout (see: sendFailIfNoSpace policy entry) (5.16)</td></tr></tbody></table></div><p>&#160;</p><h2 id="VirtualDestinations-CompositeDestinations">Composite Destinations</h2><p>Composite Destinations allow for one-to-many relationships on individual d
 estinations; the main use case is for <em>composite queues</em>. For example when a message is sent to queue A you may want to forward it also to queues B and C and topic D. Composite destinations are then a mapping from a virtual destination to a collection of other physical destinations. In this case the mapping is broker side and the client is unaware of the mapping between the destinations. This is different from client side <a shape="rect" href="composite-destinations.html">Composite Destinations</a> where the client uses a URL notation to specify the actual physical destinations that a message must be sent to.</p><p>The following <a shape="rect" class="external-link" href="http://svn.apache.org/repos/asf/incubator/activemq/trunk/activemq-unit-tests/src/test/resources/org/apache/activemq/broker/virtual/composite-queue.xml">example</a> shows how to set up a <strong>&lt;compositeQueue/&gt;</strong> element in the XML configuration so that when a message is sent to <code>MY.QUEUE<
 /code> then it is really forwarded to the physical queue <code>FOO</code> and the topic <code>BAR</code>.</p><pre><span style="color: rgb(0,0,0);">&lt;destinationInterceptors&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;virtualDestinationInterceptor&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;virtualDestinations&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;compositeQueue name="MY.QUEUE"&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;forwardTo&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;queue physicalName="FOO" /&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;topic physicalName="BAR" /&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;/forwardTo&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;/compositeQueue&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;/virtualDestinations&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;/virtualDestinationInterceptor&gt;</
 span></pre><pre><span style="color: rgb(0,0,0);">&lt;/destinationInterceptors&gt;</span></pre><p>&#160;</p><p>By default, subscribers cannot consume messages directly from a composite queue or topic - it is a logical construct only. Given the configuration above, subscribers can only consume messages from <code>FOO</code> and <code>BAR</code>; but not <code>MY.QUEUE</code>.</p><p>This behaviour can be altered to implement use cases such as watching a queue by sending the same messages to a notification topic (wire tapping), by setting the optionally set <code>forwardOnly</code> attribute to false.</p><pre>&lt;compositeQueue name="IncomingOrders" forwardOnly="false"&gt; </pre><pre>   &lt;forwardTo&gt;</pre><pre>    &lt;topic physicalName="Notifications" /&gt;</pre><pre>   &lt;/forwardTo&gt;</pre><pre> &lt;/compositeQueue&gt;</pre><p>&#160;</p><p>Messages sent to <code>IncomingOrders</code> will all be copied and forwarded to <code>Notifications</code>, before being placed on the phys
 ical <code>IncomingOrders</code> queue for consumption by subscribers.</p><p>Where the <code>forwardOnly</code> attribute is not defined or is set to <code>true</code>, there is no logical difference between a <code>compositeQueue</code> and a <code>compositeTopic</code> - they can be used interchangeably. It is only when a composite destination is made physical through the use of <code>forwardOnly</code> that the choice of <code>compositeTopic</code>/<code>compositeQueue</code> has an impact on behavior.</p><h3 id="VirtualDestinations-Usingfiltereddestinations">Using filtered destinations</h3><p>From Apache ActiveMQ <strong>4.2</strong> onwards you can now use selectors to define virtual destinations.</p><p>You may wish to create a virtual destination which forwards messages to multiple destinations but applying a selector first to decide if the message really does have to go to a particular destination.</p><p>The following example shows how a message sent to the virtual destinatio
 n <strong>MY.QUEUE</strong> will be forwarded to <strong>FOO</strong> and <strong>BAR</strong> if the selectors match</p><pre>&lt;destinationInterceptors&gt; &lt;virtualDestinationInterceptor&gt; &lt;virtualDestinations&gt; </pre><pre>   &lt;compositeQueue name="MY.QUEUE"&gt;</pre><pre>    &lt;forwardTo&gt;</pre><pre>     &lt;filteredDestination selector="odd = 'yes'" queue="FOO"/&gt;</pre><pre>     &lt;filteredDestination selector="i = 5" topic="BAR"/&gt;</pre><pre>    &lt;/forwardTo&gt;</pre><pre>  &lt;/compositeQueue&gt;</pre><pre>&lt;/virtualDestinations&gt; &lt;/virtualDestinationInterceptor&gt; &lt;/destinationInterceptors&gt;</pre><p>&#160;</p><h2 id="VirtualDestinations-AvoidingDuplicateMessageinaNetworkofBrokers">Avoiding Duplicate Message in a Network of Brokers</h2><p>You have to make sure that the messages sent to the <strong>Consumer.*.VirtualTopic.&gt;</strong> destination are not forwarded when you're using both queue-based and non-queue based subscribers to the virtu
 al topic (that is, if you have normal topic subscribers to the virtual topic). If you use Virtual Topics in a network of brokers, it is likely you will get duplicate messages if you use the default network configuration. This is because a network node will not only forward message sent to the virtual topic, but also the associated physical queues. To fix this, you should disable forwarding messages on the associated physical queues.</p><p>Here is an example of how to do that:</p><pre><span style="color: rgb(0,0,0);">&lt;networkConnectors&gt; &lt;networkConnector uri="static://(<a shape="rect" href="tcp://localhost:61617" rel="nofollow">tcp://localhost:61617</a>)"&gt;</span></pre><pre><span style="color: rgb(0,0,0);"> &lt;excludedDestinations&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;queue physicalName="Consumer.*.VirtualTopic.&gt;"/&gt; </span></pre><pre><span style="color: rgb(0,0,0);"> &lt;/excludedDestinations&gt; </span></pre><pre><span style="color: rgb(0,0,0)
 ;">&lt;/networkConnector&gt; &lt;/networkConnectors&gt;</span></pre><p>&#160;</p></div>
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