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<title>2. RabbitMQ Binder Overview</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="multi_spring-cloud-stream-binder-rabbit.html" title="Spring Cloud Stream RabbitMQ Binder Reference Guide"><link rel="up" href="multi__reference_guide.html" title="Part I. Reference Guide"><link rel="prev" href="multi__usage.html" title="1. Usage"><link rel="next" href="multi__configuration_options.html" title="3. Configuration Options"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2. RabbitMQ Binder Overview</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi__usage.html">Prev</a> </td><th width="60%" align="center">Part I. Reference Guide</th><td width="20%" align="right"> <a accesskey="n" href="multi__configuration_options.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_rabbitmq_binder_overview" href="#_rabbitmq_binder_overview"></a>2. RabbitMQ Binder Overview</h2></div></div></div><p>The following simplified diagram shows how the RabbitMQ binder operates:</p><div class="figure"><a name="d0e39" href="#d0e39"></a><p class="title"><b>Figure 2.1. RabbitMQ Binder</b></p><div class="figure-contents"><div class="mediaobject"><img src="http://raw.github.com/spring-cloud/spring-cloud-stream-binder-rabbit/master/docs/src/main/asciidoc/images/rabbit-binder.png" alt="rabbit binder"></div></div></div><br class="figure-break"><p>By default, the RabbitMQ Binder implementation maps each destination to a <code class="literal">TopicExchange</code>.
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For each consumer group, a <code class="literal">Queue</code> is bound to that <code class="literal">TopicExchange</code>.
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Each consumer instance has a corresponding RabbitMQ <code class="literal">Consumer</code> instance for its group’s <code class="literal">Queue</code>.
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For partitioned producers and consumers, the queues are suffixed with the partition index and use the partition index as the routing key.
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For anonymous consumers (those with no <code class="literal">group</code> property), an auto-delete queue (with a randomized unique name) is used.</p><p>By using the optional <code class="literal">autoBindDlq</code> option, you can configure the binder to create and configure dead-letter queues (DLQs) (and a dead-letter exchange <code class="literal">DLX</code>, as well as routing infrastructure).
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By default, the dead letter queue has the name of the destination, appended with <code class="literal">.dlq</code>.
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If retry is enabled (<code class="literal">maxAttempts > 1</code>), failed messages are delivered to the DLQ after retries are exhausted.
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If retry is disabled (<code class="literal">maxAttempts = 1</code>), you should set <code class="literal">requeueRejected</code> to <code class="literal">false</code> (the default) so that failed messages are routed to the DLQ, instead of being re-queued.
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In addition, <code class="literal">republishToDlq</code> causes the binder to publish a failed message to the DLQ (instead of rejecting it).
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This feature lets additional information (such as the stack trace in the <code class="literal">x-exception-stacktrace</code> header) be added to the message in headers.
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See the <a class="link" href="multi__configuration_options.html#spring-cloud-stream-rabbit-frame-max-headroom"><code class="literal">frameMaxHeadroom</code> property</a> for information about truncated stack traces.
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This option does not need retry enabled.
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You can republish a failed message after just one attempt.
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Starting with version 1.2, you can configure the delivery mode of republished messages.
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See the <a class="link" href="multi__configuration_options.html#spring-cloud-stream-rabbit-republish-delivery-mode"><code class="literal">republishDeliveryMode</code> property</a>.</p><p>If the stream listener throws an <code class="literal">ImmediateAcknowledgeAmqpException</code>, the DLQ is bypassed and the message simply discarded.
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Starting with version 2.1, this is true regardless of the setting of <code class="literal">republishToDlq</code>; previously it was only the case when <code class="literal">republishToDlq</code> was <code class="literal">false</code>.</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left">Important</th></tr><tr><td align="left" valign="top"><p>Setting <code class="literal">requeueRejected</code> to <code class="literal">true</code> (with <code class="literal">republishToDlq=false</code> ) causes the message to be re-queued and redelivered continually, which is likely not what you want unless the reason for the failure is transient.
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In general, you should enable retry within the binder by setting <code class="literal">maxAttempts</code> to greater than one or by setting <code class="literal">republishToDlq</code> to <code class="literal">true</code>.</p></td></tr></table></div><p>See <a class="xref" href="multi__configuration_options.html#rabbit-binder-properties" title="3.1 RabbitMQ Binder Properties">Section 3.1, “RabbitMQ Binder Properties”</a> for more information about these properties.</p><p>The framework does not provide any standard mechanism to consume dead-letter messages (or to re-route them back to the primary queue).
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Some options are described in <a class="xref" href="multi_rabbit-dlq-processing.html" title="6. Dead-Letter Queue Processing">Chapter 6, <i>Dead-Letter Queue Processing</i></a>.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>When multiple RabbitMQ binders are used in a Spring Cloud Stream application, it is important to disable 'RabbitAutoConfiguration' to avoid the same configuration from <code class="literal">RabbitAutoConfiguration</code> being applied to the two binders.
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You can exclude the class by using the <code class="literal">@SpringBootApplication</code> annotation.</p></td></tr></table></div><p>Starting with version 2.0, the <code class="literal">RabbitMessageChannelBinder</code> sets the <code class="literal">RabbitTemplate.userPublisherConnection</code> property to <code class="literal">true</code> so that the non-transactional producers avoid deadlocks on consumers, which can happen if cached connections are blocked because of a <a class="link" href="https://www.rabbitmq.com/memory.html" target="_top">memory alarm</a> on the broker.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>Currently, a <code class="literal">multiplex</code> consumer (a single consumer listening to multiple queues) is only supported for message-driven conssumers; polled consumers can only retrieve messages from a single queue.</p></td></tr></table></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi__usage.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="multi__reference_guide.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="multi__configuration_options.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">1. Usage </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud-stream-binder-rabbit.html">Home</a></td><td width="40%" align="right" valign="top"> 3. Configuration Options</td></tr></table></div></body></html> |