| <div role="region" aria-label="Skip to main content"><a class="skipToContent_fXgn" href="#__docusaurus_skipToContent_fallback">Skip to main content</a></div><nav aria-label="Main" class="navbar navbar--fixed-top"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Toggle navigation bar" aria-expanded="false" class="navbar__toggle clean-btn" type="button"><svg width="30" height="30" viewBox="0 0 30 30" aria-hidden="true"><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><a class="navbar__brand" href="/"><div class="navbar__logo"><img src="/img/Apache_RocketMQ_logo.svg.png" alt="My Site Logo" class="themedImage_ToTc themedImage--light_HNdA"><img src="/img/Apache_RocketMQ_logo.svg.png" alt="My Site Logo" class="themedImage_ToTc themedImage--dark_i4oU"></div><b class="navbar__title text--truncate">Apache RocketMQ</b></a></div><div class="navbar__items navbar__items--right"><a href="https://github.com/apache/rocketmq" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a><div class="navbar__item dropdown dropdown--hoverable dropdown--right"><a href="#" aria-haspopup="true" aria-expanded="false" role="button" class="navbar__link"><svg viewBox="0 0 24 24" width="20" height="20" aria-hidden="true" class="iconLanguage_nlXk"><path fill="currentColor" d="M12.87 15.07l-2.54-2.51.03-.03c1.74-1.94 2.98-4.17 3.71-6.53H17V4h-7V2H8v2H1v1.99h11.17C11.5 7.92 10.44 9.75 9 11.35 8.07 10.32 7.3 9.19 6.69 8h-2c.73 1.63 1.73 3.17 2.98 4.56l-5.09 5.02L4 19l5-5 3.11 3.11.76-2.04zM18.5 10h-2L12 22h2l1.12-3h4.75L21 22h2l-4.5-12zm-2.62 7l1.62-4.33L19.12 17h-3.24z"></path></svg>English</a><ul class="dropdown__menu"><li><a href="/zh/docs/domainModel/04message" target="_self" rel="noopener noreferrer" class="dropdown__link" lang="zh">简体中文</a></li><li><a href="/docs/domainModel/04message" target="_self" rel="noopener noreferrer" class="dropdown__link dropdown__link--active" lang="en">English</a></li></ul></div><div class="navbar__item dropdown dropdown--hoverable dropdown--right"><a href="#" aria-haspopup="true" aria-expanded="false" role="button" class="navbar__link">Docs</a><ul class="dropdown__menu"><li><a aria-current="page" class="dropdown__link dropdown__link--active" href="/docs/">5.0</a></li><li><a class="dropdown__link" href="/docs/4.x/">4.x</a></li></ul></div><a class="navbar__item navbar__link" href="/download">Download</a><div class="navbar__item dropdown dropdown--hoverable dropdown--right"><a href="#" aria-haspopup="true" aria-expanded="false" role="button" class="navbar__link">Blog</a><ul class="dropdown__menu"><li><a class="dropdown__link" href="/blog">User Cases</a></li><li><a class="dropdown__link" href="/events">Activity</a></li><li><a class="dropdown__link" href="/release-notes">Change Log</a></li><li><a class="dropdown__link" href="/news">RocketMQ News</a></li></ul></div><div class="navbar__item dropdown dropdown--hoverable dropdown--right"><a href="#" aria-haspopup="true" aria-expanded="false" role="button" class="navbar__link">Community</a><ul class="dropdown__menu"><li><a class="dropdown__link" href="/contact">Join Community</a></li><li><a class="dropdown__link" href="/origin">Origin</a></li><li><a class="dropdown__link" href="/team">Teams</a></li><li><a class="dropdown__link" href="/docs/contributionGuide/01how-to-contribute">Contributions</a></li><li><a class="dropdown__link" href="/enterprise">Enterprises</a></li></ul></div><div class="toggle_vylO colorModeToggle_DEke"><button class="clean-btn toggleButton_gllP toggleButtonDisabled_aARS" type="button" disabled="" title="Switch between dark and light mode (currently light mode)" aria-label="Switch between dark and light mode (currently light mode)" aria-live="polite"><svg viewBox="0 0 24 24" width="24" height="24" class="lightToggleIcon_pyhR"><path fill="currentColor" d="M12,9c1.65,0,3,1.35,3,3s-1.35,3-3,3s-3-1.35-3-3S10.35,9,12,9 M12,7c-2.76,0-5,2.24-5,5s2.24,5,5,5s5-2.24,5-5 S14.76,7,12,7L12,7z M2,13l2,0c0.55,0,1-0.45,1-1s-0.45-1-1-1l-2,0c-0.55,0-1,0.45-1,1S1.45,13,2,13z M20,13l2,0c0.55,0,1-0.45,1-1 s-0.45-1-1-1l-2,0c-0.55,0-1,0.45-1,1S19.45,13,20,13z M11,2v2c0,0.55,0.45,1,1,1s1-0.45,1-1V2c0-0.55-0.45-1-1-1S11,1.45,11,2z M11,20v2c0,0.55,0.45,1,1,1s1-0.45,1-1v-2c0-0.55-0.45-1-1-1C11.45,19,11,19.45,11,20z M5.99,4.58c-0.39-0.39-1.03-0.39-1.41,0 c-0.39,0.39-0.39,1.03,0,1.41l1.06,1.06c0.39,0.39,1.03,0.39,1.41,0s0.39-1.03,0-1.41L5.99,4.58z M18.36,16.95 c-0.39-0.39-1.03-0.39-1.41,0c-0.39,0.39-0.39,1.03,0,1.41l1.06,1.06c0.39,0.39,1.03,0.39,1.41,0c0.39-0.39,0.39-1.03,0-1.41 L18.36,16.95z M19.42,5.99c0.39-0.39,0.39-1.03,0-1.41c-0.39-0.39-1.03-0.39-1.41,0l-1.06,1.06c-0.39,0.39-0.39,1.03,0,1.41 s1.03,0.39,1.41,0L19.42,5.99z M7.05,18.36c0.39-0.39,0.39-1.03,0-1.41c-0.39-0.39-1.03-0.39-1.41,0l-1.06,1.06 c-0.39,0.39-0.39,1.03,0,1.41s1.03,0.39,1.41,0L7.05,18.36z"></path></svg><svg viewBox="0 0 24 24" width="24" height="24" class="darkToggleIcon_wfgR"><path fill="currentColor" d="M9.37,5.51C9.19,6.15,9.1,6.82,9.1,7.5c0,4.08,3.32,7.4,7.4,7.4c0.68,0,1.35-0.09,1.99-0.27C17.45,17.19,14.93,19,12,19 c-3.86,0-7-3.14-7-7C5,9.07,6.81,6.55,9.37,5.51z M12,3c-4.97,0-9,4.03-9,9s4.03,9,9,9s9-4.03,9-9c0-0.46-0.04-0.92-0.1-1.36 c-0.98,1.37-2.58,2.26-4.4,2.26c-2.98,0-5.4-2.42-5.4-5.4c0-1.81,0.89-3.42,2.26-4.4C12.92,3.04,12.46,3,12,3L12,3z"></path></svg></button></div><div class="searchBox_ZlJk"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20" aria-hidden="true"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"></span></button></div></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div id="__docusaurus_skipToContent_fallback" class="main-wrapper mainWrapper_z2l0 docsWrapper_BCFX"><button aria-label="Scroll back to top" class="clean-btn theme-back-to-top-button backToTopButton_sjWU" type="button"></button><div class="docPage__5DB"><aside class="theme-doc-sidebar-container docSidebarContainer_b6E3"><div class="sidebarViewport_Xe31"><div class="sidebar_njMd"><nav aria-label="Docs sidebar" class="menu thin-scrollbar menu_SIkG"><ul class="theme-doc-sidebar-menu menu__list"><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/">Introduction</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/quickStart/01quickstart">Quick Start</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="/docs/domainModel/01main">Domain Model</a></div><ul style="display:block;overflow:visible;height:auto" class="menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/01main">Domain Model</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/02topic">Topic</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/03messagequeue">Message Queue</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="/docs/domainModel/04message">Message</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/04producer">Producer</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/07consumergroup">Consumer Group</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/08consumer">Consumer</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-2 menu__list-item"><a class="menu__link" tabindex="0" href="/docs/domainModel/09subscription">Subscription</a></li></ul></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/featureBehavior/01normalmessage">Feature Behavior</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/deploymentOperations/01deploy">Deployment & Operations</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/observability/01metrics">Observability</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/sdk/01overview">Client SDK</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/bestPractice/01bestpractice">Best Practice</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/eventbridge/01RocketMQEventBridgeConcepts">RocketMQ EventBridge</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/mqtt/01RocketMQMQTTOverview">RocketMQ MQTT</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/connect/01RocketMQ Connect Overview">RocketMQ Connect</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/streams/01RocketMQ Streams Overview">RocketMQ Streams</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="/docs/contributionGuide/01how-to-contribute">Contribution Guide</a></div></li></ul></nav></div></div></aside><main class="docMainContainer_gTbr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li 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">Domain Model</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">Message</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>Message</h1><p>This section describes the definition, model relationship, internal attributes, and behavior constraints of messages in Apache RocketMQ. This topic also provides usage notes for messages.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="definition">Definition<a href="#definition" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>A message is the smallest unit of data transmission in Apache RocketMQ. A producer encapsulates the load and extended attributes of business data into messages and sends the messages to a Apache RocketMQ broker. Then, the broker delivers the messages to the consumer based on the relevant semantics.</p><p>The characteristics of the message model in Apache RocketMQ are:</p><ul><li><strong>Immutability</strong>: A message is an event that is generated. After the message is generated, the content of the message does not change. Even if the message passes through a transmission channel, the content of the message remains the same. The messages that consumers obtain are read-only messages.</li></ul><ul><li><strong>Persistence</strong>: By default, Apache RocketMQ persists messages. The received messages are stored in the storage file of the Apache RocketMQ broker to ensure that the messages can be traced and restored if system failures occur.</li></ul><h2 class="anchor anchorWithStickyNavbar_LWe7" id="model-relationship">Model relationship<a href="#model-relationship" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>The following figure shows the position of messages in the domain model of Apache RocketMQ.<img loading="lazy" alt="消息" src="/assets/images/archiforqueue-dd6788b33bf2fc96b4a1dab83a1b0d71.png" width="2358" height="920" class="img_ev3q"></p><ol><li><p>Messages are initialized by producers and are sent to the Apache RocketMQ broker.</p></li><li><p>Messages are stored in queues in the order in which the messages are received on the Apache RocketMQ broker.</p></li><li><p>Consumers obtain and consume messages from the Apache RocketMQ broker based on the specified subscriptions.</p></li></ol><h2 class="anchor anchorWithStickyNavbar_LWe7" id="internal-attributes">Internal attributes<a href="#internal-attributes" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p><strong>System retention attributes</strong></p><p><strong>Topic name</strong></p><ul><li><p>Definition: the name of the topic to which a message belongs. The topic name is globally unique in a cluster. For more information, see <a href="/docs/domainModel/02topic">Topic</a>.</p></li><li><p>Values: obtained from the SDK of the client.</p></li></ul><p><strong>Message type</strong></p><ul><li><p>Definition: the type of a message.</p></li><li><p>Values: obtained from the SDK of the client. Apache RocketMQ supports the following message types:</p><ul><li><p>Normal: <a href="/docs/featureBehavior/01normalmessage">Normal messages</a>. A normal message does not require special semantics and is not correlated with other normal messages.</p></li><li><p>FIFO: <a href="/docs/featureBehavior/03fifomessage">Fifo messages</a>. Apache RocketMQ uses a message group to determine the order of a specified set of messages. The messages are delivered in the order in which they are sent.</p></li><li><p>Delay: <a href="/docs/featureBehavior/02delaymessage">Delayed messages</a>. You can specify a delay to make messages available to consumers only after the delay has elapsed, instead of delivering messages immediately when they are produced.</p></li><li><p>Transaction: <a href="/docs/featureBehavior/04transactionmessage">Transaction messages</a>. Apache RocketMQ supports distributed transaction messages and ensures transaction consistency of database updates and message calls.</p></li></ul></li></ul><p><strong>Message queue</strong></p><ul><li><p>Definition: the queue to which a message belongs. For more information, see <a href="/docs/domainModel/03messagequeue">Message queues</a>.</p></li><li><p>Values: specified and populated by the broker.</p></li></ul><p><strong>Message offset</strong></p><ul><li><p>Definition: the location where the current message is stored in the queue. For more information, see <a href="/docs/featureBehavior/09consumerprogress">Working mechanism</a>.</p></li><li><p>Values: specified and populated by the broker. Valid values: 0 to Long.Max.</p></li></ul><p><strong>Message ID</strong></p><ul><li><p>Definition: the unique identifier of a message. The ID of each message is globally unique in the cluster.</p></li><li><p>Values: automatically generated by the producer client. A message ID is a string of 32 characters that consists of digits and uppercase letters.</p></li></ul><p><strong>(Optional) Message keys</strong></p><ul><li><p>Definition: the list of index keys for messages. You can configure different keys to distinguish between messages and quickly find messages.</p></li><li><p>Values: defined by the producer client.</p></li></ul><p><strong>(Optional) Message tag</strong></p><ul><li><p>Definition: the tag that is used to filter messages. Consumers can filter messages by tags and receive only messages that contain specified tags.</p></li><li><p>Values: defined by the producer client.</p></li><li><p>Constraint: Only one tag can be specified for each message.</p></li></ul><p><strong>(Optional) Scheduled time</strong></p><ul><li><p>Definition: the millisecond-level timestamp that is used when a message triggers delayed delivery in a scheduled time scenario. For more information, see <a href="/docs/featureBehavior/02delaymessage">Delayed messages</a>.</p></li><li><p>Values: defined by the message producer.</p></li><li><p>Constraint: The maximum duration is 40 days.</p></li></ul><p><strong>Message sending time</strong></p><ul><li><p>Definition: the local millisecond-level timestamp of the producer client when the message is sent.</p></li><li><p>Values: populated by the producer client.</p></li><li><p>Note: The client time may be different from the broker time. In this case, the message sending time is based on the client time.</p></li></ul><p><strong>Message store timestamp</strong></p><ul><li><p>Definition: the local millisecond-level timestamp of the Apache RocketMQ broker when the message is stored.</p><p>For delay messages and transaction messages, the message retention time is the broker time that is displayed for the consumer when the message takes effect.</p></li><li><p>Values: populated by the broker.</p></li><li><p>Note: The client time may be different from the broker time. In this case, the message retention time is based on the broker time.</p></li></ul><p><strong>Retry times</strong></p><ul><li><p>Definition: the number of times that the Apache RocketMQ broker redelivers a message after the message fails to be consumed. After each retry, the maximum number of retries is increased by one. For more information, see <a href="/docs/featureBehavior/10consumerretrypolicy">Consumption retry</a>.</p></li><li><p>Values: labeled by the broker. The first time that a message is consumed, the number of retries is zero. The first time that a message fails to be consumed, the number of retries is one.</p></li></ul><p><strong>Custom attributes for messages</strong></p><p><strong>Custom attributes</strong></p><ul><li><p>Definition: the extended information that can be specified by the producer.</p></li><li><p>Values: specified by the producer based on key-value pairs from a string.</p></li></ul><p><strong>Message load</strong></p><ul><li><p>Definition: the actual message data of the service message.</p></li><li><p>Values: serialized by the producer and transmitted in binary bytes.</p></li><li><p>Constraints: see <a href="/docs/introduction/03limits">Parameter limits</a>.</p></li></ul><h2 class="anchor anchorWithStickyNavbar_LWe7" id="behavior-constraints">Behavior constraints<a href="#behavior-constraints" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>The size of a message cannot exceed the upper limit. If the size of a message exceeds the corresponding upper limit, the message fails to be sent.</p><p>The following describes the default limits for messages:</p><ul><li>max size of message: 4 MB</li></ul><h2 class="anchor anchorWithStickyNavbar_LWe7" id="usage-notes">Usage notes<a href="#usage-notes" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p><strong>Overloaded transmission is not recommended for a single message.</strong></p><p>Apache RocketMQ is a messaging middleware that transmits data for business events. If the size of a message is large, the network transmission layer may be overloaded. This affects retries upon errors and throttling. We recommend that you limit the data size of a single message event.</p><p>If an overloaded transmission is required in the production environment, we recommend that you split the message based on a fixed size or use the file storage method.</p><p><strong>Immutability of messages</strong></p><p>Messages cannot be modified in Apache RocketMQ broker versions 5.x and the messages that consumers obtain are read-only messages. No strong constraints related to immutability are imposed on versions 3.x and 4.x. We recommend that you re-initialize messages if you want to transmit messages.</p><ul><li><p>Correct example:</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">Message m = Consumer.receive();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">Message m2= MessageBuilder.buildFrom(m);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">Producer.send(m2);</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>Incorrect example：</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">Message m = Consumer.receive();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">m.update()；</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">Producer.send(m);</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-5.0/03-domainModel/04message.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/domainModel/03messagequeue"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Message Queue</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/domainModel/04producer"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Producer</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="#definition" class="table-of-contents__link toc-highlight">Definition</a></li><li><a href="#model-relationship" class="table-of-contents__link toc-highlight">Model relationship</a></li><li><a href="#internal-attributes" class="table-of-contents__link toc-highlight">Internal attributes</a></li><li><a href="#behavior-constraints" class="table-of-contents__link toc-highlight">Behavior constraints</a></li><li><a href="#usage-notes" class="table-of-contents__link toc-highlight">Usage notes</a></li></ul></div></div></div></div></main></div></div><footer class="footer footer--dark"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title">Learn</div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/docs/domainModel/01main">Introduction</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/quickStart/01quickstart">Installation</a></li><li class="footer__item"><a class="footer__link-item" href="/version">Migration from 4.x to 5.0</a></li></ul></div><div class="col footer__col"><div class="footer__title">Community</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://twitter.com/ApacheRocketMQ" target="_blank" rel="noopener noreferrer" class="footer__link-item">Twitter<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://github.com/apache/rocketmq" target="_blank" rel="noopener noreferrer" class="footer__link-item">Github</a></li><li class="footer__item"><a href="https://github.com/apache/rocketmq" target="_blank" rel="noopener noreferrer" class="footer__link-item">Help</a></li></ul></div><div class="col footer__col"><div class="footer__title">More</div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/blog">Blog</a></li><li class="footer__item"><a class="footer__link-item" href="/release-notes">Changelog</a></li><li class="footer__item"><a href="https://github.com/apache/rocketmq" target="_blank" rel="noopener noreferrer" class="footer__link-item">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://twitter.com/docusaurus" target="_blank" rel="noopener noreferrer" class="footer__link-item">Twitter<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div><div class="col footer__col"><div class="footer__title">Legal</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://www.apache.org/licenses/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Licenses<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/security/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Security<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/foundation/thanks.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Thanks<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/foundation/sponsorship.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Sponsorship<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div></div><div class="footer__bottom text--center"><div class="margin-bottom--sm"><a href="https://rocketmq.apache.org/" rel="noopener noreferrer" class="footerLogoLink_BH7S"><img src="/img/Apache_RocketMQ_logo.svg.png" alt="Meta Open Source Logo" class="themedImage_ToTc themedImage--light_HNdA footer__logo"><img src="/img/Apache_RocketMQ_logo.svg.png" alt="Meta Open Source Logo" class="themedImage_ToTc themedImage--dark_i4oU footer__logo"></a></div><div class="footer__copyright">Copyright © 2022 The Apache Software Foundation. Licensed under the Apache License, Version 2.0.</div></div></div></footer></div> |
