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From build...@apache.org
Subject svn commit: r942137 - in /websites/production/activemq/content: cache/main.pageCache message-redelivery-and-dlq-handling.html
Date Tue, 03 Mar 2015 12:21:40 GMT
Author: buildbot
Date: Tue Mar  3 12:21:39 2015
New Revision: 942137

Log:
Production update by buildbot for activemq

Modified:
    websites/production/activemq/content/cache/main.pageCache
    websites/production/activemq/content/message-redelivery-and-dlq-handling.html

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

Modified: websites/production/activemq/content/message-redelivery-and-dlq-handling.html
==============================================================================
--- websites/production/activemq/content/message-redelivery-and-dlq-handling.html (original)
+++ websites/production/activemq/content/message-redelivery-and-dlq-handling.html Tue Mar
 3 12:21:39 2015
@@ -82,31 +82,15 @@
   <tbody>
         <tr>
         <td valign="top" width="100%">
-<div class="wiki-content maincontent"><h3 id="MessageRedeliveryandDLQHandling-Overview">Overview</h3>
-
-<p>Messages are redelivered to a client when <strong>any</strong> of the
following occurs:</p>
-<ol><li>A transacted session is used and rollback() is called.</li><li>A
transacted session is closed before commit is called.</li><li>A session is using
CLIENT_ACKNOWLEDGE and Session.recover() is called.</li></ol>
-
-
-<p>The broker transmits the default delivery policy that he prefers to a client connection
in his BrokerInfo command packet.  But the client can override the policy settings by using
the ActiveMQConnection.getRedeliveryPolicy() method:</p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: java; gutter: false" type="syntaxhighlighter"><![CDATA[
-RedeliveryPolicy policy = connection.getRedeliveryPolicy();
+<div class="wiki-content maincontent"><h3 id="MessageRedeliveryandDLQHandling-Overview">Overview</h3><p>Messages
are redelivered to a client when <strong>any</strong> of the following occurs:</p><ol><li>A
transacted session is used and rollback() is called.</li><li>A transacted session
is closed before commit is called.</li><li>A session is using CLIENT_ACKNOWLEDGE
and Session.recover() is called.</li></ol><p>The broker transmits the default
delivery policy that he prefers to a client connection in his BrokerInfo command packet. But
the client can override the policy settings by using the ActiveMQConnection.getRedeliveryPolicy()
method:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
+<script class="theme: Default; brush: java; gutter: false" type="syntaxhighlighter"><![CDATA[RedeliveryPolicy
policy = connection.getRedeliveryPolicy();
 policy.setInitialRedeliveryDelay(500);
 policy.setBackOffMultiplier(2);
 policy.setUseExponentialBackOff(true);
 policy.setMaximumRedeliveries(2);
 ]]></script>
-</div></div>
-
-<p>Once a message's redelivery attempts exceeds the maximumRedeliveries configured
for the <a shape="rect" href="redelivery-policy.html">Redelivery Policy</a>, a
"Poison ack" is sent back to the broker letting him know that the message was considered a
poison pill.  The Broker then takes the message and sends it to a Dead Letter Queue so that
it can be analyzed later on. </p>
-
-<p>The default Dead Letter Queue in ActiveMQ is called ActiveMQ.DLQ; all undeliverable
messages will get sent to this queue and this can be difficult to manage. So, you can set
an "individualDeadLetterStrategy" in the destination policy map of the <code>activemq.xml</code>
configuration file, which allows you to specify a specific dead letter queue prefix for a
given queue or topic. You can apply this strategy using wild card if you like so that all
queues get their own dead-letter queue, as is shown in the example below. </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;broker...&gt;
+</div></div><p>Once a message's redelivery attempts exceeds the maximumRedeliveries
configured for the <a shape="rect" href="redelivery-policy.html">Redelivery Policy</a>,
a "Poison ack" is sent back to the broker letting him know that the message was considered
a poison pill. The Broker then takes the message and sends it to a Dead Letter Queue so that
it can be analyzed later on.</p><p>The default Dead Letter Queue in ActiveMQ is
called ActiveMQ.DLQ; all undeliverable messages will get sent to this queue and this can be
difficult to manage. So, you can set an "individualDeadLetterStrategy" in the destination
policy map of the <code>activemq.xml</code> configuration file, which allows you
to specify a specific dead letter queue prefix for a given queue or topic. You can apply this
strategy using wild card if you like so that all queues get their own dead-letter queue, as
is shown in the example below.</p><div class="code panel pdl" style="border-width:
1px;"><div class="codeContent
  panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;broker...&gt;
   &lt;destinationPolicy&gt;
     &lt;policyMap&gt;
       &lt;policyEntries&gt;
@@ -127,17 +111,8 @@ policy.setMaximumRedeliveries(2);
   ...
 &lt;/broker&gt;
 ]]></script>
-</div></div>
-
-<p>See the <a shape="rect" href="redelivery-policy.html">Redelivery Policy</a>
section for some more detail on the policy options.</p>
-
-<h3 id="MessageRedeliveryandDLQHandling-AutomaticallyDiscardExpiredMessages">Automatically
Discard Expired Messages </h3>
-
-<p>Some folks simply need expired messages to be discarded instead of sent to the DLQ
(i.e., skip the DLQ entirely). This simplifies the management of the DLQ so that you're not
sifting through loads of expired messages to find messages with real problems. To tell ActiveMQ
to just discard expired messages, configure the <code>processExpired</code> property
to false on a dead letter strategy: </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;broker...&gt;
+</div></div><p>See the <a shape="rect" href="redelivery-policy.html">Redelivery
Policy</a> section for some more detail on the policy options.</p><h3 id="MessageRedeliveryandDLQHandling-AutomaticallyDiscardExpiredMessages">Automatically
Discard Expired Messages</h3><p>Some folks simply need expired messages to be
discarded instead of sent to the DLQ (i.e., skip the DLQ entirely). This simplifies the management
of the DLQ so that you're not sifting through loads of expired messages to find messages with
real problems. To tell ActiveMQ to just discard expired messages, configure the <code>processExpired</code>
property to false on a dead letter strategy:</p><div class="code panel pdl" style="border-width:
1px;"><div class="codeContent panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;broker...&gt;
   &lt;destinationPolicy&gt;
    &lt;policyMap&gt;
      &lt;policyEntries&gt;
@@ -158,15 +133,8 @@ policy.setMaximumRedeliveries(2);
 ...
 &lt;/broker&gt;
 ]]></script>
-</div></div>
-
-<h3 id="MessageRedeliveryandDLQHandling-Placenon-persistentmessagesontothedead-letterqueue">Place
non-persistent messages onto the dead-letter queue</h3>
-
-<p>By default, ActiveMQ will not place undeliverable <em>non-persistent</em>
messages on the dead-letter queue.  The rationale for this behavior is that if the application
doesn't care enough to make the message persistent, then there is little or no value in recording
that the message was undeliverable. If you do want to place non-persistent messages on the
dead-letter queue, then you should set <code>processNonPersistent="true"</code>
on the dead-letter strategy. </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;broker...&gt;
+</div></div><h3 id="MessageRedeliveryandDLQHandling-Placenon-persistentmessagesontothedead-letterqueue">Place
non-persistent messages onto the dead-letter queue</h3><p>By default, ActiveMQ
will not place undeliverable <em>non-persistent</em> messages on the dead-letter
queue. The rationale for this behavior is that if the application doesn't care enough to make
the message persistent, then there is little or no value in recording that the message was
undeliverable. If you do want to place non-persistent messages on the dead-letter queue, then
you should set <code>processNonPersistent="true"</code> on the dead-letter strategy.</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;broker...&gt;
   &lt;destinationPolicy&gt;
    &lt;policyMap&gt;
      &lt;policyEntries&gt;
@@ -186,17 +154,24 @@ policy.setMaximumRedeliveries(2);
 ...
 &lt;/broker&gt;
 ]]></script>
-</div></div>
-
-<h3 id="MessageRedeliveryandDLQHandling-TheDiscardingDLQPlugin">The Discarding DLQ
Plugin </h3>
-
-<p>A very simple yet very useful plugin to the broker. This plugin allows the configuration
of queues and topics, all or matched based on <a shape="rect" class="external-link" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/regex/Pattern.html"
rel="nofollow">Java SE regular expressions</a>, to drop messages that have been sent
to the DLQ. This is extremely useful when using <a shape="rect" href="slow-consumer-handling.html#SlowConsumerHandling-ConstantPendingMessageLimitStrategy">constant
pending message limit strategy</a> or the other eviction rules, but you don't want to
incur the overhead of yet another consumer to clear the DLQ. </p>
-
-<p>Below is an example of a basic configuration to drop everything: </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;beans&gt; 
+</div></div><h3 id="MessageRedeliveryandDLQHandling-SettingexpirationonmessagesintheDLQ">Setting
expiration on messages in the DLQ</h3><p>By default, ActiveMQ will never expire
messages sent to the DLQ but from v5.12, the deadLetterStrategy supports an expiration attribute
where the value is in milliseconds. Note, be selective in how this is applied. In particular
do not apply expiration to your DLQ destinations by setting expiration on a default or inclusive
wildcard policy entry. If a DLQ entry expires and forwards to the same or another DLQ with
expiry, you will introduce a loop that can be problematic if the strategy audit is disabled
or it's sliding window is exceeded.</p><div class="code panel pdl" style="border-width:
1px;"><div class="codeContent panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;broker...&gt;
+  &lt;destinationPolicy&gt;
+   &lt;policyMap&gt;
+     &lt;policyEntries&gt;
+       &lt;policyEntry queue=&quot;QueueWhereItIsOkToExpireDLQEntries&quot;&gt;
+         &lt;deadLetterStrategy&gt;
+           &lt;.... expiration=&quot;300000&quot; /&gt;
+         &lt;/deadLetterStrategy&gt;
+       &lt;/policyEntry&gt;
+     &lt;/policyEntries&gt;
+   &lt;/policyMap&gt;
+  &lt;/destinationPolicy&gt;
+...
+&lt;/broker&gt;
+]]></script>
+</div></div><h3 id="MessageRedeliveryandDLQHandling-TheDiscardingDLQPlugin">The
Discarding DLQ Plugin</h3><p>A very simple yet very useful plugin to the broker.
This plugin allows the configuration of queues and topics, all or matched based on <a shape="rect"
class="external-link" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/regex/Pattern.html"
rel="nofollow">Java SE regular expressions</a>, to drop messages that have been sent
to the DLQ. This is extremely useful when using <a shape="rect" href="slow-consumer-handling.html#SlowConsumerHandling-ConstantPendingMessageLimitStrategy">constant
pending message limit strategy</a> or the other eviction rules, but you don't want to
incur the overhead of yet another consumer to clear the DLQ.</p><p>Below is an
example of a basic configuration to drop everything:</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;beans&gt;

   &lt;broker ...&gt;
     &lt;plugins&gt;
       &lt;discardingDLQBrokerPlugin dropAll=&quot;true&quot; dropTemporaryTopics=&quot;true&quot;
dropTemporaryQueues=&quot;true&quot; /&gt;
@@ -204,13 +179,8 @@ policy.setMaximumRedeliveries(2);
   &lt;/broker&gt;
 &lt;/beans&gt;
 ]]></script>
-</div></div>
-
-<p>Below is a slightly more complex example: </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;beans&gt; 
+</div></div><p>Below is a slightly more complex example:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;beans&gt;

   &lt;broker ...&gt;
     &lt;plugins&gt;
       &lt;discardingDLQBrokerPlugin dropOnly=&quot;MY.EXAMPLE.TOPIC.29 MY.EXAMPLE.QUEUE.87&quot;
reportInterval=&quot;1000&quot; /&gt;
@@ -218,16 +188,8 @@ policy.setMaximumRedeliveries(2);
   &lt;/broker&gt;
 &lt;/beans&gt;
 ]]></script>
-</div></div>
-
-<ul><li>Notice that destination names are space delimited.</li><li>The
reportInterval property is used to denote how frequently do we output how many messages we
have dropped - use 0 to disable.</li></ul>
-
-
-<p>Below is an even more complex example: </p>
-
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;beans&gt; 
+</div></div><ul><li>Notice that destination names are space delimited.</li><li>The
reportInterval property is used to denote how frequently do we output how many messages we
have dropped - use 0 to disable.</li></ul><p>Below is an even more complex
example:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;beans&gt;

   &lt;broker ...&gt;
     &lt;plugins&gt;
       &lt;discardingDLQBrokerPlugin dropOnly=&quot;MY.EXAMPLE.TOPIC.[0-9]{3} MY.EXAMPLE.QUEUE.[0-9]{3}&quot;
reportInterval=&quot;3000&quot; /&gt;
@@ -235,22 +197,8 @@ policy.setMaximumRedeliveries(2);
   &lt;/broker&gt;
 &lt;/beans&gt;
 ]]></script>
-</div></div>
-
-<ul><li>Notice that the destination names use regular expressions. These match
the number 000..999 at the end of each destination name.</li></ul>
-
-
-<p>For more information, see the source code for the <a shape="rect" class="external-link"
href="https://svn.apache.org/repos/asf/activemq/trunk/activemq-broker/src/main/java/org/apache/activemq/plugin/DiscardingDLQBrokerPlugin.java">DiscardingDLQBrokerPlugin</a>
and the <a shape="rect" class="external-link" href="https://svn.apache.org/repos/asf/activemq/trunk/activemq-broker/src/main/java/org/apache/activemq/plugin/DiscardingDLQBroker.java">DiscardingDLQBroker</a></p>
-
-
-<h3 id="MessageRedeliveryandDLQHandling-BrokerRedelivery(v5.7)">Broker Redelivery (v5.7)</h3>
-<p>Typically a consumer handles redelivery so that it can maintain message order while
a message appears as inflight on the broker.<br clear="none">
-This means that redelivery is limited to a single consumer unless that consumer terminates.
In this way the broker is unaware of redelivery.<br clear="none">
-With broker redelivery, it is possible to have the broker redeliver a message after a delay
using a resend. This is implemented by a broker plugin that handles dead letter processing
by redelivery via the scheduler. This is useful when total message order is not important
and where through put and load distribution among consumers is. With broker redelivery, messages
that fail delivery to a given consumer can get immediately re-dispatched.<br clear="none">
-The feature is enabled via xml configuration of the form:</p>
-<div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent
pdl">
-<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[
-&lt;broker xmlns=&quot;http://activemq.apache.org/schema/core&quot;    schedulerSupport=&quot;true&quot;
&gt;
+</div></div><ul><li>Notice that the destination names use regular
expressions. These match the number 000..999 at the end of each destination name.</li></ul><p>For
more information, see the source code for the <a shape="rect" class="external-link" href="https://svn.apache.org/repos/asf/activemq/trunk/activemq-broker/src/main/java/org/apache/activemq/plugin/DiscardingDLQBrokerPlugin.java">DiscardingDLQBrokerPlugin</a>
and the <a shape="rect" class="external-link" href="https://svn.apache.org/repos/asf/activemq/trunk/activemq-broker/src/main/java/org/apache/activemq/plugin/DiscardingDLQBroker.java">DiscardingDLQBroker</a></p><h3
id="MessageRedeliveryandDLQHandling-BrokerRedelivery(v5.7)">Broker Redelivery (v5.7)</h3><p>Typically
a consumer handles redelivery so that it can maintain message order while a message appears
as inflight on the broker.<br clear="none"> This means that redelivery is limited to
a single consumer unless that consumer terminates. In this way the broker is unawar
 e of redelivery.<br clear="none"> With broker redelivery, it is possible to have the
broker redeliver a message after a delay using a resend. This is implemented by a broker plugin
that handles dead letter processing by redelivery via the scheduler. This is useful when total
message order is not important and where through put and load distribution among consumers
is. With broker redelivery, messages that fail delivery to a given consumer can get immediately
re-dispatched.<br clear="none"> The feature is enabled via xml configuration of the
form:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
+<script class="theme: Default; brush: xml; gutter: false" type="syntaxhighlighter"><![CDATA[&lt;broker
xmlns=&quot;http://activemq.apache.org/schema/core&quot;    schedulerSupport=&quot;true&quot;
&gt;
         .... 
         &lt;plugins&gt;
             &lt;redeliveryPlugin fallbackToDeadLetter=&quot;true&quot; sendToDlqIfMaxRetriesExceeded=&quot;true&quot;&gt;
@@ -271,16 +219,7 @@ redeliveryDelay=&quot;10000&quot; /&gt;
             &lt;/redeliveryPlugin&gt;
         &lt;/plugins&gt;
 ]]></script>
-</div></div>
-
-<p>The familiar <a shape="rect" href="redelivery-policy.html">Redelivery Policy</a>
has been extended to take a matching destination.<br clear="none">
-fallbackToDeadLetter controls the action when there is no matching redeliver policy for a
destination. Defaults to true so regular DLQ processing ensues.<br clear="none">
-sendToDlqIfMaxRetriesExceeded controls the action when the retry limit is exceeded. Defaults
to true so regular DLQ processing ensues. When false, the message is dropped.</p>
-
-<ul><li>Note: broker schedulerSupport must be enabled for this feature to work.</li></ul>
-
-
-</div>
+</div></div><p>The familiar <a shape="rect" href="redelivery-policy.html">Redelivery
Policy</a> has been extended to take a matching destination.<br clear="none">
fallbackToDeadLetter controls the action when there is no matching redeliver policy for a
destination. Defaults to true so regular DLQ processing ensues.<br clear="none"> sendToDlqIfMaxRetriesExceeded
controls the action when the retry limit is exceeded. Defaults to true so regular DLQ processing
ensues. When false, the message is dropped.</p><ul><li>Note: broker schedulerSupport
must be enabled for this feature to work.</li></ul></div>
         </td>
         <td valign="top">
           <div class="navigation">



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