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这篇文章主要为大家展示了“RocketMQ中push consumer启动之资源初始化的示例分析”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“RocketMQ中push consumer启动之资源初始化的示例分析”这篇文章吧。
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RocketMQ的消费者支持两种消费模式：拉模式（pull）和推模式（push）。推模式在底层也是通过pull机制来实现的，push consumer会周期性地批量拉取broker上的消息，然后按指定的batch方式调用注册的listener，模拟“推”的效果。因此，推模式是拉模式的超集。
push consumer在启动过程中，首先是完成资源初始化，然后就触发消息拉取，最后将消息推送到注册的listener上实现消息消费。
push consumer的启动流程如下图：
核心逻辑就在DefaultMQPushConsumerImpl.start方法中：
public synchronized void start() throws MQClientException {
switch (this.serviceState) {
case CREATE_JUST:
log.info("the consumer [{}] start beginning. messageModel={}, isUnitMode={}", this.defaultMQPushConsumer.getConsumerGroup(),
this.defaultMQPushConsumer.getMessageModel(), this.defaultMQPushConsumer.isUnitMode());
this.serviceState = ServiceState.START_FAILED;
// 1. 配置检查，若存在非法配置则抛出异常
this.checkConfig();
// 2. 复制订阅关系。将DefaultMQPushConsumer中的订阅关系复制到RebalanceImpl中；复制message listener
this.copySubscription();
if (this.defaultMQPushConsumer.getMessageModel() == MessageModel.CLUSTERING) {
this.defaultMQPushConsumer.changeInstanceNameToPID();
}
// 3. 初始化MQClientInstance
this.mQClientFactory = MQClientManager.getInstance().getOrCreateMQClientInstance(this.defaultMQPushConsumer, this.rpcHook);
// 4. 初始化RebalanceImpl
this.rebalanceImpl.setConsumerGroup(this.defaultMQPushConsumer.getConsumerGroup());
this.rebalanceImpl.setMessageModel(this.defaultMQPushConsumer.getMessageModel());
this.rebalanceImpl.setAllocateMessageQueueStrategy(this.defaultMQPushConsumer.getAllocateMessageQueueStrategy());
this.rebalanceImpl.setmQClientFactory(this.mQClientFactory);
// 5. 初始化PullAPIWrapper
this.pullAPIWrapper = new PullAPIWrapper(
mQClientFactory,
this.defaultMQPushConsumer.getConsumerGroup(), isUnitMode());
this.pullAPIWrapper.registerFilterMessageHook(filterMessageHookList);
// 6. 初始化OffsetStore
if (this.defaultMQPushConsumer.getOffsetStore() != null) {
this.offsetStore = this.defaultMQPushConsumer.getOffsetStore();
} else {
switch (this.defaultMQPushConsumer.getMessageModel()) {
case BROADCASTING:
this.offsetStore = new LocalFileOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
case CLUSTERING:
this.offsetStore = new RemoteBrokerOffsetStore(this.mQClientFactory, this.defaultMQPushConsumer.getConsumerGroup());
break;
default:
break;
}
this.defaultMQPushConsumer.setOffsetStore(this.offsetStore);
}
this.offsetStore.load();
// 7. 初始化CosumeMessageService
if (this.getMessageListenerInner() instanceof MessageListenerOrderly) {
this.consumeOrderly = true;
this.consumeMessageService =
new ConsumeMessageOrderlyService(this, (MessageListenerOrderly) this.getMessageListenerInner());
} else if (this.getMessageListenerInner() instanceof MessageListenerConcurrently) {
this.consumeOrderly = false;
this.consumeMessageService =
new ConsumeMessageConcurrentlyService(this, (MessageListenerConcurrently) this.getMessageListenerInner());
}
this.consumeMessageService.start();
// 8. 将本consumer注册到MQClientInstance中，并启动
boolean registerOK = mQClientFactory.registerConsumer(this.defaultMQPushConsumer.getConsumerGroup(), this);
if (!registerOK) {
this.serviceState = ServiceState.CREATE_JUST;
this.consumeMessageService.shutdown(defaultMQPushConsumer.getAwaitTerminationMillisWhenShutdown());
throw new MQClientException("The consumer group[" + this.defaultMQPushConsumer.getConsumerGroup()
+ "] has been created before, specify another name please." + FAQUrl.suggestTodo(FAQUrl.GROUP_NAME_DUPLICATE_URL),
null);
}
mQClientFactory.start();
log.info("the consumer [{}] start OK.", this.defaultMQPushConsumer.getConsumerGroup());
this.serviceState = ServiceState.RUNNING;
break;
case RUNNING:
case START_FAILED:
case SHUTDOWN_ALREADY:
throw new MQClientException("The PushConsumer service state not OK, maybe started once, "
+ this.serviceState
+ FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK),
null);
default:
break;
}
// 9. 订阅topic路由信息
this.updateTopicSubscribeInfoWhenSubscriptionChanged();
// 10. 检查client配置并开始向broker发生心跳
this.mQClientFactory.checkClientInBroker();
this.mQClientFactory.sendHeartbeatToAllBrokerWithLock();
// 11. 更新订阅关系，触发消息拉取
this.mQClientFactory.rebalanceImmediately();
}以上是“RocketMQ中push consumer启动之资源初始化的示例分析”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注创新互联行业资讯频道！
