| <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/4.x/producer/06message5" target="_self" rel="noopener noreferrer" class="dropdown__link" lang="zh">简体中文</a></li><li><a href="/docs/4.x/producer/06message5" 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 aria-current="page" class="dropdown__link dropdown__link--active" 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/4.x/">Introduction</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/4.x/producer/01concept1">Producer</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/4.x/producer/01concept1">Core Concept</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/4.x/producer/02message1">Simple Message Sending</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/4.x/producer/03message2">Ordered Message Sending</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/4.x/producer/04message3">Delayed Message Sending</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/4.x/producer/05message4">Batch Message Sending</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/4.x/producer/06message5">Transactional Message Sending</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/4.x/consumer/01concept2">Consumer</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/4.x/deployment/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/4.x/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/4.x/parameterConfiguration/01local">Parameter Configuration</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/4.x/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/4.x/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/4.x/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/4.x/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/4.x/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">Producer</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">Transactional Message Sending</span><meta itemprop="position" content="2"></li></ul></nav><span class="theme-doc-version-badge badge badge--secondary">Version: 4.x</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>Transactional Message Sending</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>In some scenarios where there is a strong need for data consistency, Apache RocketMQ transactional messages can be used to ensure consistency of upstream and downstream data.</p><p><img loading="lazy" alt="事务消息1" src="/assets/images/事务消息1-15b51f54e4cb4280459be1df277c288e.png" width="1656" height="782" class="img_ev3q"></p><p>Transactional messages are send in two phases. At first, a half message will be delivered, which refers to a message is successfully sent to the MQ server, but the server did not receive the second acknowledgement of the message from the Producer, then the message will be marked as “temporarily undeliverable” state.</p><p>The local transaction will be executed if the message is sent successfully, and a half message status (commit or rollback) will be delivered to the Broker depending on the local transaction results.</p><p>If the second acknowledgement of a transactional message is lost due to network flashback, Producer restart, etc., the Broker will find the message which is in "half message" state for a long time, and take the initiative to check the transaction status of the message (Commit or Rollback) from the Producer. Therefore, the downstream will receive the message if the local transaction is executed successfully, otherwise it will not. This ultimately ensures the consistency of the upstream and downstream data.</p><p>The detailed execute flow of the transactional message is shown in the following diagram:</p><p><img loading="lazy" alt="事务消息2" src="/assets/images/事务消息2-2673a99678f13a471b8fc0bd4ab3bf3a.png" width="1996" height="544" class="img_ev3q"></p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="transactional-message-sending-procedure">Transactional Message Sending Procedure<a href="#transactional-message-sending-procedure" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><ol><li><p>The Producer sends the half message to the <code>RocketMQ Broker</code>.</p></li><li><p>After the <code>RocketMQ Broker</code> persists the message successfully, it returns an Ack to the Producer confirming that the message was sent successfully and it is a half message.</p></li><li><p>The Producer starts executing the local transaction.</p></li><li><p>The Producer submits a second acknowledgement (Commit or Rollback) to the server based on the result of the local transaction, and the server receives the acknowledgment and processes the logic as follows.</p><ul><li>If the second acknowledgement result is Commit: the server marks the half message as deliverable and delivers it to the Consumer.</li><li>If the second acknowledgement result is Rollback: the server will rollback the transaction and will not deliver the half message to the Consumer.</li></ul></li><li><p>In the special case of network disconnection or the Producer restarts, if the server does not receive the second acknowledgment result from the Producer, or the second acknowledgment result received by the server is Unknown, the server will initiate a rollback message to a Producer after a fixed time.</p></li></ol><p>The procedure of the transaction status check are as follows.</p><ol><li>After receiving the transaction status check request, the Producer needs to verify the final result of the local transaction of the corresponding message.</li><li>The producer submits the second acknowledgment again based on the final result of the local transaction, and the server side will still processes the half message according to step 4.</li></ol><h2 class="anchor anchorWithStickyNavbar_LWe7" id="example">Example<a href="#example" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><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 TransactionProducer {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static void main(String[] args) throws MQClientException, InterruptedException {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> TransactionListener transactionListener = new TransactionListenerImpl();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> TransactionMQProducer producer = new TransactionMQProducer("please_rename_unique_group_name");</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> ExecutorService executorService = new ThreadPoolExecutor(2, 5, 100, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(2000), new ThreadFactory() {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> @Override</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public Thread newThread(Runnable r) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Thread thread = new Thread(r);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> thread.setName("client-transaction-msg-check-thread");</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return thread;</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" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> producer.setExecutorService(executorService);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> producer.setTransactionListener(transactionListener);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> producer.start();</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"> String[] tags = new String[] {"TagA", "TagB", "TagC", "TagD", "TagE"};</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> for (int i = 0; i < 10; i++) {</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"> Message msg =</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> new Message("TopicTest", tags[i % tags.length], "KEY" + i,</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> SendResult sendResult = producer.sendMessageInTransaction(msg, null);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> System.out.printf("%s%n", sendResult);</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"> Thread.sleep(10);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> } catch (MQClientException | UnsupportedEncodingException 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"> }</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"> for (int i = 0; i < 100000; i++) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Thread.sleep(1000);</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"> producer.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" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> static class TransactionListenerImpl implements TransactionListener {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> private AtomicInteger transactionIndex = new AtomicInteger(0);</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"> private ConcurrentHashMap<String, Integer> localTrans = new ConcurrentHashMap<>();</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"> @Override</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public LocalTransactionState executeLocalTransaction(Message msg, Object arg) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> int value = transactionIndex.getAndIncrement();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> int status = value % 3;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> localTrans.put(msg.getTransactionId(), status);</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return LocalTransactionState.UNKNOW;</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" style="display:inline-block"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> @Override</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public LocalTransactionState checkLocalTransaction(MessageExt msg) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Integer status = localTrans.get(msg.getTransactionId());</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> if (null != status) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> switch (status) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> case 0:</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return LocalTransactionState.UNKNOW;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> case 1:</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return LocalTransactionState.COMMIT_MESSAGE;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> case 2:</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return LocalTransactionState.ROLLBACK_MESSAGE;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> default:</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return LocalTransactionState.COMMIT_MESSAGE;</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"> return LocalTransactionState.COMMIT_MESSAGE;</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="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><p>Transactional messages are no longer sent by DefaultMQProducer, but using <code>TransactionMQProducer</code>. The above sample sets the thread pool for the transactional message check, if not, one will be generated by default. The most important thing is to implement the <code>TransactionListener</code> interface and pass <code>TransactionMQProducer</code> into it.</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 TransactionListener interface is defined 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">public interface TransactionListener {</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"> * When send transactional prepare(half) message succeed, this method will be invoked to execute local transaction.</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"> * @param msg Half(prepare) message</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * @param arg Custom business parameter</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * @return Transaction state</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"> LocalTransactionState executeLocalTransaction(final Message msg, final Object arg);</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"> /**</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * When no response to prepare(half) message. broker will send check message to check the transaction status, and this</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * method will be invoked to get local transaction status.</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"> * @param msg Check message</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> * @return Transaction state</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"> LocalTransactionState checkLocalTransaction(final MessageExt msg);</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="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></div><p><code>executeLocalTransaction</code> is the method that executes the local transaction after the half message has been sent successfully. After executing the local transaction, the following three states can be returned in this method.</p><ul><li><code>LocalTransactionState.COMMIT_MESSAGE</code>: the transaction is committed, allowing the consumer to consume the message.</li><li><code>LocalTransactionState.ROLLBACK_MESSAGE</code>: the transaction is rolled back, and the message will be discarded without being allowed to be consumed.</li><li><code>LocalTransactionState.UNKNOW</code>: temporarily unable to determine the state. After waiting for a fixed time, the Broker send the transaction status check message back to the producer.</li></ul><p><code>checkLocalTransaction</code> is a method to check the transaction state on the Broker side because the second acknowledgement is not received. Transaction status check rule: After the execution of the local transaction is completed, if the local transaction returns LocalTransactionState.UNKNOW status to the Broker, or the Producer exits causing no status returned from the Producer. Then the Broker will initiate a transaction status check message to the Producer, and it will check again at regular intervals if the transaction status is still not obtained.</p><div class="theme-admonition theme-admonition-caution alert alert--warning admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 16 16"><path fill-rule="evenodd" d="M8.893 1.5c-.183-.31-.52-.5-.887-.5s-.703.19-.886.5L.138 13.499a.98.98 0 0 0 0 1.001c.193.31.53.501.886.501h13.964c.367 0 .704-.19.877-.5a1.03 1.03 0 0 0 .01-1.002L8.893 1.5zm.133 11.497H6.987v-2.003h2.039v2.003zm0-3.004H6.987V5.987h2.039v4.006z"></path></svg></span>caution</div><div class="admonitionContent_S0QG"><p>It is important to note that the ProducerGroupName of a transactional message cannot be set arbitrarily. Transactional messages have a transaction status check mechanism. If the original Producer is found to have crashed and collapsed, the Broker will contact other Producer instances within the same Producer group to check the local transaction execution and Commit or Rollback half messages.</p></div></div></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/02-producer/06message5.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/4.x/producer/05message4"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Batch Message Sending</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/4.x/consumer/01concept2"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Core Concept</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="#transactional-message-sending-procedure" class="table-of-contents__link toc-highlight">Transactional Message Sending Procedure</a></li><li><a href="#example" class="table-of-contents__link toc-highlight">Example</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> |
