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RocketMQ第14篇：原理篇-订阅关系的一致性
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<div style="display:none"></div> 订阅关系的一致性指的是，同一个消费者组（Group ID相同）下所有Consumer实例所订阅的Topic与Tag及对消息的处理逻辑必须完全一致。否则，消息消费的逻辑就会混乱，甚至导致消息丢失。 ## 1、正确订阅关系 多个消费者组订阅了多个Topic，并且每个消费者组里的多个消费者实例的订阅关系保持了一致。  ## 2、错误订阅关系 一个消费者组订阅了多个Topic，但是该消费者组里的多个Consumer实例的订阅关系并没有保持一致。  ### 2.1、订阅了不同Topic 该例中的错误在于，同一个消费者组中的两个Consumer实例订阅了不同的Topic。 Consumer实例1-1：（订阅了topic为jodie_test_A，tag为所有的消息） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_1"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_A", "*", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` Consumer实例1-2：（订阅了topic为jodie_test_B，tag为所有的消息） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_1"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_B", "*", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` ### 2.2、订阅了不同Tag 该例中的错误在于，同一个消费者组中的两个Consumer订阅了相同Topic的不同Tag。 Consumer实例2-1：（订阅了topic为jodie_test_A，tag为TagA的消息） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_2"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_A", "TagA", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` Consumer实例2-2：（订阅了topic为jodie_test_A，tag为所有的消息） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_2"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_A", "*", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` ### 2.3、订阅了不同数量的Topic 该例中的错误在于，同一个消费者组中的两个Consumer订阅了不同数量的Topic。 Consumer实例3-1：（该Consumer订阅了两个Topic） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_3"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_A", "TagA", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); consumer.subscribe("jodie_test_B", "TagB", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` Consumer实例3-2：（该Consumer订阅了一个Topic） ```java Properties properties = new Properties(); properties.put(PropertyKeyConst.GROUP_ID, "GID_jodie_test_3"); Consumer consumer = ONSFactory.createConsumer(properties); consumer.subscribe("jodie_test_A", "TagB", new MessageListener() { public Action consume(Message message, ConsumeContext context) { System.out.println(message.getMsgID()); return Action.CommitMessage; } }); ``` <a style="display:none" target="_blank" href="https://mp.weixin.qq.com/s/_S1DD2JADnXvpexxaBwLLg" style="color:red; font-size:20px; font-weight:bold">继续收门徒，亲手带，月薪 4W 以下的可以来找我</a> ## 最新资料 1. <a href="https://mp.weixin.qq.com/s?__biz=MzkzOTI3Nzc0Mg==&mid=2247484964&idx=2&sn=c81bce2f26015ee0f9632ddc6c67df03&scene=21#wechat_redirect" target="_blank">尚硅谷 Java 学科全套教程（总 207.77GB）</a> 2. <a href="https://mp.weixin.qq.com/s?__biz=MzkwOTAyMTY2NA==&mid=2247484192&idx=1&sn=505f2faaa4cc911f553850667749bcbb&scene=21#wechat_redirect" target="_blank">2021 最新版 Java 微服务学习线路图 + 视频</a> 3. <a href="https://mp.weixin.qq.com/s?__biz=MzkwOTAyMTY2NA==&mid=2247484573&idx=1&sn=7f3d83892186c16c57bc0b99f03f1ffd&scene=21#wechat_redirect" target="_blank">阿里技术大佬整理的《Spring 学习笔记.pdf》</a> 4. <a href="https://mp.weixin.qq.com/s?__biz=MzkwOTAyMTY2NA==&mid=2247484544&idx=2&sn=c1dfe907cfaa5b9ae8e66fc247ccbe84&scene=21#wechat_redirect" target="_blank">阿里大佬的《MySQL 学习笔记高清.pdf》</a> 5. <a href="https://mp.weixin.qq.com/s?__biz=MzkwOTAyMTY2NA==&mid=2247485167&idx=1&sn=48d75c8e93e748235a3547f34921dfb7&scene=21#wechat_redirect" target="_blank">2021 版 java 高并发常见面试题汇总.pdf</a> 6. <a href="https://mp.weixin.qq.com/s?__biz=MzkwOTAyMTY2NA==&mid=2247485664&idx=1&sn=435f9f515a8f881642820d7790ad20ce&scene=21#wechat_redirect" target="_blank">Idea 快捷键大全.pdf</a> 
相关专辑：
RocketMQ专题