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itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Ordered 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>Ordered Message Sending</h1><h2 class="anchor anchorWithStickyNavbar_LWe7" id="ordered-message-introduction">Ordered Message Introduction<a href="#ordered-message-introduction" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>Ordered messages have strict requirements on the order in which they are sent and consumed. </p><p>For a given Topic, messages are published and consumed strictly on a first-in-first-out (FIFO) basis, i.e., messages published first will be consumed first. Furthermore, as shown in the following figure, partitioned ordered messages are supported in Apache RocketMQ. The messages can be partitioned according to a certain criterion (e.g., ShardingKey). Messages with the same ShardingKey are assigned to the identical queue and consumed in order. |
| <img loading="lazy" alt="顺序消息发送" src="/assets/images/顺序消息发送-a80d08ef7dacd4e936c3f6992a1369e5.png" width="2546" height="610" class="img_ev3q"></p><p>Ordered messages are also used in a wide range of application scenarios, such as the example of creating orders, the same order generation, payment, and shipment should be executed sequentially. In the case of simple messages, the messages of Order A may be polled and sent to different queues. The messages of different queues will not be able to maintain order. In contrast, ordered messages are sent by routing the sequence of messages with the same ShardingKey (same order number) to a logical queue.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="ordered-message-sample-code">Ordered Message Sample Code<a href="#ordered-message-sample-code" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>The ordered message sample code 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">public class Producer {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> public static void main(String[] args) throws UnsupportedEncodingException {</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"> DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");</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 < 100; i++) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> int orderId = i % 10;</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.send(msg, new MessageQueueSelector() {</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 MessageQueue select(List<MessageQueue> mqs, Message msg, Object arg) {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> Integer id = (Integer) arg;</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> int index = id % mqs.size();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> return mqs.get(index);</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"> }, orderId);</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"> System.out.printf("%s%n", sendResult);</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.shutdown();</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> } catch (MQClientException | RemotingException | MQBrokerException | InterruptedException 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">}</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>The difference here is mainly the call to the <code>SendResult send(Message msg, MessageQueueSelector selector, Object arg)</code> method, where MessageQueueSelector is the queue selector and arg is a Object in Java that can be passed in as a sorting criterion for sending partitioned messages.</p><div class="theme-admonition theme-admonition-tip alert alert--success admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_S0QG"><p>MessageQueueSelector interface 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">public interface MessageQueueSelector {</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> MessageQueue select(final List<MessageQueue> mqs, final Message msg, final Object arg);</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>In the interface, mqs is the queue, msg is the message, and arg is the object passed in, the queue that message are sent to will be returned. In the above example, the orderId is used as the partitioning criterion, and the remainder of all queues is used to send messages with the same orderId to the same queue.</p></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="consistency-of-ordered-messages">Consistency of Ordered Messages<a href="#consistency-of-ordered-messages" class="hash-link" aria-label="Direct link to heading" title="Direct link to heading"></a></h2><p>If a Broker drops out, does the total number of queues change at that point? </p><p>If a change occurs, messages with the same ShardingKey will be sent to a different queue causing disorder. If no change occurs, messages will be sent to the queue of the offline Broker, which is bound to fail. Therefore, Apache RocketMQ provides two modes, to guarantee strict order over availability, create Topic by specifying the <code>-o</code> parameter (--order) to be true, which represents ordered messages:</p><div class="language-shell codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-shell codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token plain">$ </span><span class="token function" style="color:#d73a49">sh</span><span class="token plain"> bin/mqadmin updateTopic -c DefaultCluster -t TopicTest -o </span><span class="token boolean" style="color:#36acaa">true</span><span class="token plain"> -n </span><span class="token number" style="color:#36acaa">127.0</span><span class="token plain">.0.1:9876</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">create topic to </span><span class="token number" style="color:#36acaa">127.0</span><span class="token plain">.0.1:10911 success.</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">TopicConfig </span><span class="token punctuation" style="color:#393A34">[</span><span class="token plain">topicName</span><span class="token operator" style="color:#393A34">=</span><span class="token plain">TopicTest, </span><span class="token assign-left variable" style="color:#36acaa">readQueueNums</span><span class="token operator" style="color:#393A34">=</span><span class="token number" style="color:#36acaa">8</span><span class="token plain">, </span><span class="token assign-left variable" style="color:#36acaa">writeQueueNums</span><span class="token operator" style="color:#393A34">=</span><span class="token number" style="color:#36acaa">8</span><span class="token plain">, </span><span class="token assign-left variable" style="color:#36acaa">perm</span><span class="token operator" style="color:#393A34">=</span><span class="token plain">RW-, </span><span class="token assign-left variable" style="color:#36acaa">topicFilterType</span><span class="token operator" style="color:#393A34">=</span><span class="token plain">SINGLE_TAG, </span><span class="token assign-left variable" style="color:#36acaa">topicSysFlag</span><span class="token operator" style="color:#393A34">=</span><span class="token number" style="color:#36acaa">0</span><span class="token plain">, </span><span class="token assign-left variable" style="color:#36acaa">order</span><span class="token operator" style="color:#393A34">=</span><span class="token plain">true, </span><span class="token assign-left variable" style="color:#36acaa">attributes</span><span class="token operator" style="color:#393A34">=</span><span class="token plain">null</span><span class="token punctuation" style="color:#393A34">]</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>Secondly, make sure that the configuration <code>orderMessageEnable</code> and <code>returnOrderTopicConfigToBroker</code> in the NameServer must be true. If either of the above conditions is not met, availability is guaranteed rather than strict order.</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/02-producer/03message2.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/02message1"><div 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