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<title data-rh="true">Pull消费 | RocketMQ</title><meta data-rh="true" name="viewport" content="width=device-width,initial-scale=1"><meta data-rh="true" name="twitter:card" content="summary_large_image"><meta data-rh="true" property="og:url" content="https://your-docusaurus-test-site.com/zh/docs/4.x/consumer/03pull"><meta data-rh="true" name="docusaurus_locale" content="zh"><meta data-rh="true" name="docsearch:language" content="zh"><meta data-rh="true" name="docusaurus_version" content="current"><meta data-rh="true" name="docusaurus_tag" content="docs-default-current"><meta data-rh="true" name="docsearch:version" content="current"><meta data-rh="true" name="docsearch:docusaurus_tag" content="docs-default-current"><meta data-rh="true" property="og:title" content="Pull消费 | RocketMQ"><meta data-rh="true" name="description" content="在RocketMQ中有两种Pull方式，一种是比较原始Pull Consumer，它不提供相关的订阅方法，需要调用pull方法时指定队列进行拉取，并需要自己更新位点。另一种是Lite Pull Consumer，它提供了Subscribe和Assign两种方式，使用起来更加方便。"><meta data-rh="true" property="og:description" content="在RocketMQ中有两种Pull方式，一种是比较原始Pull Consumer，它不提供相关的订阅方法，需要调用pull方法时指定队列进行拉取，并需要自己更新位点。另一种是Lite Pull Consumer，它提供了Subscribe和Assign两种方式，使用起来更加方便。"><link data-rh="true" rel="icon" href="/zh/img/favicon.ico"><link data-rh="true" rel="canonical" href="https://your-docusaurus-test-site.com/zh/docs/4.x/consumer/03pull"><link data-rh="true" rel="alternate" href="https://your-docusaurus-test-site.com/zh/docs/4.x/consumer/03pull" hreflang="zh"><link data-rh="true" rel="alternate" href="https://your-docusaurus-test-site.com/docs/4.x/consumer/03pull" hreflang="en"><link data-rh="true" rel="alternate" href="https://your-docusaurus-test-site.com/docs/4.x/consumer/03pull" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://R2IYF7ETH7-dsn.algolia.net" crossorigin="anonymous"><link rel="alternate" type="application/rss+xml" href="/zh/blog/rss.xml" title="RocketMQ RSS Feed">
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1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">消费者</span><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">Pull消费</span><meta itemprop="position" content="2"></li></ul></nav><span class="theme-doc-version-badge badge badge--secondary">版本：4.x</span><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">本页总览</button></div><div class="theme-doc-markdown markdown"><h1>Pull消费</h1><p>在RocketMQ中有两种Pull方式，一种是比较原始<code>Pull Consumer</code>，它不提供相关的订阅方法，需要调用pull方法时指定队列进行拉取，并需要自己更新位点。另一种是<code>Lite Pull Consumer</code>，它提供了Subscribe和Assign两种方式，使用起来更加方便。</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="pull-consumer">Pull Consumer<a href="#pull-consumer" class="hash-link" aria-label="Pull Consumer的直接链接" title="Pull Consumer的直接链接">​</a></h2><p>Pull Consumer示例如下</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><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:#393A34"><span class="token plain">public class PullConsumerTest {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static void main(String[] args) throws MQClientException {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> DefaultMQPullConsumer consumer = new DefaultMQPullConsumer(&quot;please_rename_unique_group_name_5&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> consumer.setNamesrvAddr(&quot;127.0.0.1:9876&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> consumer.start();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> try {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> MessageQueue mq = new MessageQueue();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> mq.setQueueId(0);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> mq.setTopic(&quot;TopicTest&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> mq.setBrokerName(&quot;jinrongtong-MacBook-Pro.local&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> long offset = 26;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> PullResult pullResult = consumer.pull(mq, &quot;*&quot;, offset, 32);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> if (pullResult.getPullStatus().equals(PullStatus.FOUND)) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> System.out.printf(&quot;%s%n&quot;, pullResult.getMsgFoundList());</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> consumer.updateConsumeOffset(mq, pullResult.getNextBeginOffset());</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> } catch (Exception e) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> e.printStackTrace();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> consumer.shutdown();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" 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 viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>首先需要初始化<code>DefaultMQPullConsumer</code>并启动，然后构造需要拉取的队列<code>MessageQueue</code>，除了构造外也可以如下所示调用<code>fetchSubscribeMessageQueues</code>方法获取某个Topic的所有队列，然后挑选队列进行拉取。</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><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:#393A34"><span class="token plain">Set&lt;MessageQueue&gt; queueSet = consumer.fetchSubscribeMessageQueues(&quot;TopicTest&quot;);</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" 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 viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>找到或者构造完队列之后，调用pull方法就可以进行拉取，需要传入拉取的队列，过滤表达式，拉取的位点，最大拉取消息条数等参数。拉取完成后会返回拉取结果<code>PullResult</code>，PullResult中的PullStatus表示结果状态，如下所示</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><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:#393A34"><span class="token plain">public enum PullStatus {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> /**</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * Founded</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> */</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> FOUND,</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> /**</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * No new message can be pull</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> */</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> NO_NEW_MSG,</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> /**</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * Filtering results can not match</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> */</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> NO_MATCHED_MSG,</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> /**</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * Illegal offset,may be too big or too small</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> */</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> OFFSET_ILLEGAL</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" 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 viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>FOUND表示拉取到消息，NO_NEW_MSG表示没有发现新消息，NO_MATCHED_MSG表示没有匹配的消息，OFFSET_ILLEGAL表示传入的拉取位点是非法的，有可能偏大或偏小。如果拉取状态是FOUND，我们可以通过<code>pullResult</code>的<code>getMsgFoundList</code>方法获取拉取到的消息列表。最后，如果消费完成，通过<code>updateConsumeOffset</code>方法更新消费位点。</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="lite-pull-consumer">Lite Pull Consumer<a href="#lite-pull-consumer" class="hash-link" aria-label="Lite Pull Consumer的直接链接" title="Lite Pull Consumer的直接链接">​</a></h2><p>Lite Pull Consumer是RocketMQ 4.6.0推出的Pull Consumer，相比于原始的Pull Consumer更加简单易用，它提供了Subscribe和Assign两种模式，Subscribe模式示例如下</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><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:#393A34"><span class="token plain">public class LitePullConsumerSubscribe {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static volatile boolean running = true;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static void main(String[] args) throws Exception {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> DefaultLitePullConsumer litePullConsumer = new DefaultLitePullConsumer(&quot;lite_pull_consumer_test&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.subscribe(&quot;TopicTest&quot;, &quot;*&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.setPullBatchSize(20);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.start();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> try {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> while (running) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> List&lt;MessageExt&gt; messageExts = litePullConsumer.poll();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> System.out.printf(&quot;%s%n&quot;, messageExts);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> } finally {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.shutdown();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" 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 viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>首先还是初始化<code>DefaultLitePullConsumer</code>并设置<code>ConsumerGroupName</code>，调用subscribe方法订阅topic并启动。与Push Consumer不同的是，<code>LitePullConsumer</code>拉取消息调用的是轮询poll接口，如果能拉取到消息则返回对应的消息列表，否则返回null。通过<code>setPullBatchSize</code>可以设置每一次拉取的最大消息数量，此外如果不额外设置，<code>LitePullConsumer</code>默认是自动提交位点。在subscribe模式下，同一个消费组下的多个<code>LitePullConsumer</code>会负载均衡消费，与PushConsumer一致。</p><p>如下是Assign模式的示例</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><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:#393A34"><span class="token plain">public class LitePullConsumerAssign {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static volatile boolean running = true;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static void main(String[] args) throws Exception {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> DefaultLitePullConsumer litePullConsumer = new DefaultLitePullConsumer(&quot;please_rename_unique_group_name&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.setAutoCommit(false);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.start();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Collection&lt;MessageQueue&gt; mqSet = litePullConsumer.fetchMessageQueues(&quot;TopicTest&quot;);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> List&lt;MessageQueue&gt; list = new ArrayList&lt;&gt;(mqSet);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> List&lt;MessageQueue&gt; assignList = new ArrayList&lt;&gt;();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> for (int i = 0; i &lt; list.size() / 2; i++) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> assignList.add(list.get(i));</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.assign(assignList);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.seek(assignList.get(0), 10);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> try {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> while (running) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> List&lt;MessageExt&gt; messageExts = litePullConsumer.poll();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> System.out.printf(&quot;%s %n&quot;, messageExts);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.commitSync();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> } finally {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> litePullConsumer.shutdown();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> }</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" 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 viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>Assign模式一开始仍然是初始化<code>DefaultLitePullConsumer</code>，这里我们采用手动提交位点的方式，因此设置AutoCommit为false，然后启动consumer。与Subscribe模式不同的是，Assign模式下没有自动的负载均衡机制，需要用户自行指定需要拉取的队列，因此在例子中，先用fetchMessageQueues获取了Topic下的队列，再取前面的一半队列进行拉取，示例中还调用了seek方法，将第一个队列拉取的位点设置从10开始。紧接着进入循环不停地调用poll方法拉取消息，拉取到消息后调用commitSync方法手动提交位点。</p></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/apache/rocketmq-site/tree/new-official-website/docs/03-consumer/03pull.md" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg 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