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fill="currentColor"></path></svg></a></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><a class="breadcrumbs__link" itemprop="item" href="/docs/3.1.x/how-to-landing/"><span itemprop="name">Tutorials</span></a><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Message queue</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Use Pulsar as a message queue</h1></header><p>Message queues are essential components of many large-scale data architectures. If every single work object that passes through your system absolutely <em>must</em> be processed in spite of the slowness or downright failure of this or that system component, there&#x27;s a good chance that you&#x27;ll need a message queue to step in and ensure that unprocessed data is retained---with correct ordering---until the required actions are taken.</p><p>Pulsar is a great choice for a message queue because:</p><ul><li>it was built with <a href="/docs/3.1.x/concepts-architecture-overview/#persistent-storage">persistent message storage</a> in mind</li><li>it offers automatic load balancing across <a href="/docs/3.1.x/reference-terminology/#consumer">consumers</a> for messages on a topic (or custom load balancing if you wish)</li></ul><div class="theme-admonition theme-admonition-tip alert alert--success admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_S0QG"><p>You can use the same Pulsar installation to act as a real-time message bus and as a message queue if you wish (or just one or the other). You can set aside some topics for real-time purposes and other topics for message queue purposes (or use specific namespaces for either purpose if you wish).</p></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="client-configuration-changes">Client configuration changes<a href="#client-configuration-changes" class="hash-link" aria-label="Direct link to Client configuration changes" title="Direct link to Client configuration changes">​</a></h2><p>To use a Pulsar <a href="/docs/3.1.x/reference-terminology/#topic">topic</a> as a message queue, you should distribute the receiver load on that topic across several consumers (the optimal number of consumers depends on the load).</p><p>Each consumer must establish a <a href="/docs/3.1.x/concepts-messaging/#shared">shared subscription</a> and use the same subscription name as the other consumers (otherwise the subscription is not shared and the consumers can&#x27;t act as a processing ensemble).</p><p>If you&#x27;d like to have tight control over message dispatching across consumers, set the consumers&#x27; <strong>receiver queue</strong> size very low (potentially even to 0 if necessary). Each consumer has a receiver queue that determines how many messages the consumer attempts to fetch at a time. For example, a receiver queue of 1000 (the default) means that the consumer attempts to process 1000 messages from the topic&#x27;s backlog upon connection. Setting the receiver queue to 0 essentially means ensuring that each consumer is only doing one thing at a time.</p><div class="theme-admonition theme-admonition-tip alert alert--success admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_S0QG"><p>The receiver queue size of a partitioned topic consumer adopts the minimum one of the following two values:</p><ul><li><code>receiver_queue_size</code></li><li><code>max_total_receiver_queue_size_across_partitions</code>/<code>NumPartitions</code></li></ul></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="example">Example<a href="#example" class="hash-link" aria-label="Direct link to Example" title="Direct link to Example">​</a></h2><p>Here&#x27;s an example that uses a shared subscription.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">C++</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Go</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">org</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">apache</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">pulsar</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">client</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">api</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">Consumer</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">org</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">apache</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">pulsar</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">client</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">api</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">PulsarClient</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">org</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">apache</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">pulsar</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">client</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">api</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">SubscriptionType</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token class-name">String</span><span class="token plain"> </span><span class="token constant" style="color:rgb(189, 147, 249)">SERVICE_URL</span><span class="token plain"> </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;pulsar://localhost:6650&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token class-name">String</span><span class="token plain"> </span><span class="token constant" style="color:rgb(189, 147, 249)">TOPIC</span><span class="token plain"> </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;persistent://public/default/mq-topic-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token class-name">String</span><span class="token plain"> subscription </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;sub-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token class-name">PulsarClient</span><span class="token plain"> client </span><span class="token operator">=</span><span class="token plain"> </span><span class="token class-name">PulsarClient</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">builder</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">serviceUrl</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token constant" style="color:rgb(189, 147, 249)">SERVICE_URL</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">build</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token class-name">Consumer</span><span class="token plain"> consumer </span><span class="token operator">=</span><span class="token plain"> client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">newConsumer</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">topic</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token constant" style="color:rgb(189, 147, 249)">TOPIC</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">subscriptionName</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">subscription</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">subscriptionType</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">SubscriptionType</span><span class="token class-name punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token class-name">Shared</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">// If you&#x27;d like to restrict the receiver queue size</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">receiverQueueSize</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token number">10</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">subscribe</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">from</span><span class="token plain"> pulsar </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> Client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> ConsumerType</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">SERVICE_URL </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;pulsar://localhost:6650&quot;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">TOPIC </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;persistent://public/default/mq-topic-1&quot;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">SUBSCRIPTION </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;sub-1&quot;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">client </span><span class="token operator">=</span><span class="token plain"> Client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">SERVICE_URL</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">consumer </span><span class="token operator">=</span><span class="token plain"> client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">subscribe</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> TOPIC</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> SUBSCRIPTION</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)"># If you&#x27;d like to restrict the receiver queue size</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> receiver_queue_size</span><span class="token operator">=</span><span class="token number">10</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> consumer_type</span><span class="token operator">=</span><span class="token plain">ConsumerType</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">Shared</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-cpp codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-cpp codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token macro property directive-hash">#</span><span class="token macro property directive keyword" style="color:rgb(189, 147, 249);font-style:italic">include</span><span class="token macro property"> </span><span class="token macro property string" style="color:rgb(255, 121, 198)">&lt;pulsar/Client.h&gt;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">std</span><span class="token double-colon punctuation" style="color:rgb(248, 248, 242)">::</span><span class="token plain">string serviceUrl </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;pulsar://localhost:6650&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">std</span><span class="token double-colon punctuation" style="color:rgb(248, 248, 242)">::</span><span class="token plain">string topic </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;persistent://public/defaultmq-topic-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">std</span><span class="token double-colon punctuation" style="color:rgb(248, 248, 242)">::</span><span class="token plain">string subscription </span><span class="token operator">=</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;sub-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">Client </span><span class="token function" style="color:rgb(80, 250, 123)">client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">serviceUrl</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">ConsumerConfiguration consumerConfig</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">consumerConfig</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">setConsumerType</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">ConsumerType</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">ConsumerShared</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token comment" style="color:rgb(98, 114, 164)">// If you&#x27;d like to restrict the receiver queue size</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">consumerConfig</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">setReceiverQueueSize</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token number">10</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">Consumer consumer</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">Result result </span><span class="token operator">=</span><span class="token plain"> client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">subscribe</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">topic</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> subscription</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> consumerConfig</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> consumer</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-go codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-go codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;github.com/apache/pulsar-client-go/pulsar&quot;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> err </span><span class="token operator">:=</span><span class="token plain"> pulsar</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">NewClient</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">pulsar</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">ClientOptions</span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> URL</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;pulsar://localhost:6650&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">if</span><span class="token plain"> err </span><span class="token operator">!=</span><span class="token plain"> </span><span class="token boolean">nil</span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> log</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">Fatal</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">err</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain">consumer</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> err </span><span class="token operator">:=</span><span class="token plain"> client</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">Subscribe</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">pulsar</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">ConsumerOptions</span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> Topic</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;persistent://public/default/mq-topic-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> SubscriptionName</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"> </span><span class="token string" style="color:rgb(255, 121, 198)">&quot;sub-1&quot;</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> Type</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"> pulsar</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">Shared</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> ReceiverQueueSize</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"> </span><span class="token number">10</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">// If you&#x27;d like to restrict the receiver queue size</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">if</span><span class="token plain"> err </span><span class="token operator">!=</span><span class="token plain"> </span><span class="token boolean">nil</span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> log</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">Fatal</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">err</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" 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