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class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Best Practice</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">Consistent Subscription Relationship</span><meta itemprop="position" content="2"></li></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: 5.0</span><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"><h1>Consistent Subscription Relationship</h1><h2 class="anchor anchorWithStickyNavbar_LWe7" id="introduction">Introduction<a href="#introduction" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>Subscription relationships are a very important part of the RocketMQ domain model, used to express the control metadata for consumer consumption of messages. For a complete concept, please refer to <a href="/docs/domainModel/09subscription">Subscription Relationship Model</a>.</p><p>Subscription relationships are consistent when all Consumer instances in the same consumer group have exactly the same subscriptions to Topic and Tag. If the subscription relationships (consumer group name-Topic-Tag) are not consistent, it can lead to confusion in consuming messages and even loss of messages.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="1--examples-of-correct-subscription-relationships">1 Examples of correct subscription relationships<a href="#1--examples-of-correct-subscription-relationships" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><h3 class="anchor anchorWithStickyNavbar_LWe7" id="11--topics-subscribed-to-are-the-same-and-the-filter-expressions-are-consistent">1.1 Topics subscribed to are the same and the filter expressions are consistent<a href="#11--topics-subscribed-to-are-the-same-and-the-filter-expressions-are-consistent" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h3><p>As shown in the following figure, the three Consumer instances C1, C2, and C3 in the same ConsumerGroup have all subscribed to TopicA, and the subscriptions to TopicA's Tag are all Tag1, which meets the principle of subscription relationship consistency.</p><p><img loading="lazy" alt="1658453577894-0e64b114-cb4a-4220-a09a-62bc1f2943c6" src="/assets/images/5.0订阅关系一致-1-4cbab04c03d85562d7d144edfeb86aa6.jpeg" width="662" height="482" class="img_ev3q"></p><p><strong>Correct example code 1:</strong></p><p>C1, C2, and C3's subscription relationships are consistent, meaning that C1, C2, and C3's code for subscribing to messages must be exactly the same, and the code example is as follows:</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">PushConsumer consumer1 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer1.subscribe("TopicA", new FilterExpression("TagA", FilterExpressionType.TAG));</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">PushConsumer consumer2 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer2.subscribe("TopicA", new FilterExpression("TagA", FilterExpressionType.TAG));</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">PushConsumer consumer3 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer3.subscribe("TopicA", new FilterExpression("TagA", FilterExpressionType.TAG));</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 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><div class="theme-admonition theme-admonition-info alert alert--info admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"></path></svg></span>info</div><div class="admonitionContent_S0QG"><p>RocketMQ emphasizes consistency in subscription relationships, which means that every Consumer within the same ConsumerGroup should be consistent, because from the perspective of the server, all Consumers in a Group should be the same logical copy.</p><p>Emphasis on consistency in subscription relationships does not mean that a Consumer cannot subscribe to multiple Topics, and each Consumer can still subscribe to multiple Topics as needed, but the premise is that Consumers within the same consumer group must be consistent.</p></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="2-troubleshooting-inconsistent-subscription-relationships">2 Troubleshooting inconsistent subscription relationships<a href="#2-troubleshooting-inconsistent-subscription-relationships" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p><strong>Problem description</strong></p><p>When using the RocketMQ version of the message queue, it is possible to have inconsistent subscription relationships. The specific problems are as follows:</p><ul><li>The consistency of subscription relationships in the RocketMQ version of the message queue console is displayed as no.</li><li>Consumer instances do not receive subscribed messages.</li></ul><p><strong>Please refer to the following steps for checking</strong></p><p>You can check whether the subscription relationship of the specified Group is consistent in the Apache RocketMQ console or CLi tool. If the query result is inconsistent, please refer to the common subscription relationship inconsistency problems in this article to troubleshoot the consumption code of the Consumer instance.</p><ol><li>Check the configuration code related to subscription in your Consumer instance to ensure that all Consumer instances in the same ConsumerGroup subscribe to the same Topic and Tag.</li><li>Use the console or Cli command ConsumerConnection to check if the effective subscription relationship is consistent.</li><li>Test and confirm that the message can be consumed by the expected Consumer instance.</li></ol><h2 class="anchor anchorWithStickyNavbar_LWe7" id="3-common-issues-with-inconsistent-subscription-relationships">3 Common issues with inconsistent subscription relationships<a href="#3-common-issues-with-inconsistent-subscription-relationships" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><h3 class="anchor anchorWithStickyNavbar_LWe7" id="31-in-the-same-consumergroup-the-consumer-instances-have-different-topics-subscribed-to-applicable-to-3x-4x-sdk">3.1 In the same ConsumerGroup, the Consumer instances have different Topics subscribed to (applicable to 3.x, 4.x SDK)<a href="#31-in-the-same-consumergroup-the-consumer-instances-have-different-topics-subscribed-to-applicable-to-3x-4x-sdk" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h3><p>In the early 3.x/4.x versions of the SDK, as shown in the following figure, three Consumer instances C1, C2, and C3 in the same ConsumerGroup have subscribed to TopicA, TopicB, and TopicC respectively, and their subscribed Topics are inconsistent, which does not conform to the principle of consistent subscription.</p><div class="theme-admonition theme-admonition-note alert alert--secondary admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M6.3 5.69a.942.942 0 0 1-.28-.7c0-.28.09-.52.28-.7.19-.18.42-.28.7-.28.28 0 .52.09.7.28.18.19.28.42.28.7 0 .28-.09.52-.28.7a1 1 0 0 1-.7.3c-.28 0-.52-.11-.7-.3zM8 7.99c-.02-.25-.11-.48-.31-.69-.2-.19-.42-.3-.69-.31H6c-.27.02-.48.13-.69.31-.2.2-.3.44-.31.69h1v3c.02.27.11.5.31.69.2.2.42.31.69.31h1c.27 0 .48-.11.69-.31.2-.19.3-.42.31-.69H8V7.98v.01zM7 2.3c-3.14 0-5.7 2.54-5.7 5.68 0 3.14 2.56 5.7 5.7 5.7s5.7-2.55 5.7-5.7c0-3.15-2.56-5.69-5.7-5.69v.01zM7 .98c3.86 0 7 3.14 7 7s-3.14 7-7 7-7-3.12-7-7 3.14-7 7-7z"></path></svg></span>note</div><div class="admonitionContent_S0QG"><p>The 5.x version of the SDK now supports Consumer instances in the same ConsumerGroup subscribing to different topics.</p></div></div><p><img loading="lazy" alt="image-20220722102131073" src="/assets/images/5.0订阅关系一致-2-41010fd8c9c21c928807228caaf2d621.jpeg" width="881" height="621" class="img_ev3q"></p><h3 class="anchor anchorWithStickyNavbar_LWe7" id="32-consumer-instances-in-the-same-consumergroup-subscribe-to-the-same-topic-but-the-subscribed-tags-are-different">3.2 Consumer instances in the same ConsumerGroup subscribe to the same topic, but the subscribed tags are different.<a href="#32-consumer-instances-in-the-same-consumergroup-subscribe-to-the-same-topic-but-the-subscribed-tags-are-different" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h3><p>As shown in the following figure, the Consumer instances C1, C2, and C3 in the same ConsumerGroup all subscribe to TopicA, but C1 subscribes to Tag1 of TopicA, while C2 and C3 subscribe to Tag2 of TopicA. The subscribed tags of the same topic are inconsistent and do not conform to the consistency principle of subscription relationship.</p><p><img loading="lazy" alt="image-20220722102926055" src="/assets/images/5.0订阅关系一致-3-514888130c9907fb857a159181ff71cc.jpeg" width="867" height="608" class="img_ev3q"></p><p><strong>Error example code 2:</strong></p><ul><li><p>Consumer example 2-1：</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">PushConsumer consumer1 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer1.subscribe("TopicA", new FilterExpression("Tag1", FilterExpressionType.TAG));</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 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></li></ul><ul><li><p>Consumer example 2-2：</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">PushConsumer consumer2 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer2.subscribe("TopicA", new FilterExpression("Tag2", FilterExpressionType.TAG));</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 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></li><li><p>Consumer example 2-3：</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">PushConsumer consumer3 = provider.newPushConsumerBuilder().setConsumerGroup("GroupA").build();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">consumer3.subscribe("TopicA", new FilterExpression("Tag2", FilterExpressionType.TAG));</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 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></li></ul></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/versioned_docs/version-5.0/06-bestPractice/05subscribe.md" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><a class="pagination-nav__link pagination-nav__link--prev" href="/docs/bestPractice/04JVMOS"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">JVM/OS Configuration</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/bestPractice/06FAQ"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">FAQs</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#introduction" class="table-of-contents__link toc-highlight">Introduction</a></li><li><a href="#1--examples-of-correct-subscription-relationships" class="table-of-contents__link toc-highlight">1 Examples of correct subscription relationships</a><ul><li><a href="#11--topics-subscribed-to-are-the-same-and-the-filter-expressions-are-consistent" class="table-of-contents__link toc-highlight">1.1 Topics subscribed to are the same and the filter expressions are consistent</a></li></ul></li><li><a href="#2-troubleshooting-inconsistent-subscription-relationships" class="table-of-contents__link toc-highlight">2 Troubleshooting inconsistent subscription relationships</a></li><li><a href="#3-common-issues-with-inconsistent-subscription-relationships" class="table-of-contents__link toc-highlight">3 Common issues with inconsistent subscription relationships</a><ul><li><a href="#31-in-the-same-consumergroup-the-consumer-instances-have-different-topics-subscribed-to-applicable-to-3x-4x-sdk" class="table-of-contents__link toc-highlight">3.1 In the same ConsumerGroup, the Consumer instances have different Topics subscribed to (applicable to 3.x, 4.x SDK)</a></li><li><a href="#32-consumer-instances-in-the-same-consumergroup-subscribe-to-the-same-topic-but-the-subscribed-tags-are-different" class="table-of-contents__link toc-highlight">3.2 Consumer instances in the same ConsumerGroup subscribe to 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