目录
RebalanceService
RebalanceImpl
rebalanceByTopic
AllocateMessageQueueStrategy
updateProcessQueueTableInRebalance
入口org.apache.rocketmq.client.impl.factory.MQClientInstance#start
RocketMQ的消息消费流程分为三部分,一消息队列负载均衡,二消息的拉取,三消息的消费
RebalanceService
负载均衡定时任务的实现类
org.apache.rocketmq.client.impl.factory.MQClientInstance#doRebalance
org.apache.rocketmq.client.impl.consumer.DefaultMQPushConsumerImpl#doRebalance
RebalanceImpl
org.apache.rocketmq.client.impl.consumer.RebalanceImpl#doRebalance
rebalanceByTopic
广播模式所有队列都需订阅, 不用负载均衡,下边只关注集群模式
1、 获取所有消息队列和消费者实例;
2、 使用负载均衡算法进行分配;
3、 根据分配后最新的队列信息,进行消息拉取或停止原队列消费;
private void rebalanceByTopic(final String topic, final boolean isOrder) {
switch (messageModel) {
case BROADCASTING: {
。。。。
case CLUSTERING: {
// 从缓存表获取该Topic所有的消息队列
Set<MessageQueue> mqSet = this.topicSubscribeInfoTable.get(topic);
// 从Broker获取该消费者组所有消费者列表
List<String> cidAll = this.mQClientFactory.findConsumerIdList(topic, consumerGroup);
if (mqSet != null && cidAll != null) {
List<MessageQueue> mqAll = new ArrayList<MessageQueue>();
mqAll.addAll(mqSet);
Collections.sort(mqAll);
Collections.sort(cidAll);
// 负载均衡策略处理
AllocateMessageQueueStrategy strategy = this.allocateMessageQueueStrategy;
List<MessageQueue> allocateResult = null;
try {
allocateResult = strategy.allocate(
this.consumerGroup,
this.mQClientFactory.getClientId(),
mqAll,
cidAll);
} catch (Throwable e) {
log.error("AllocateMessageQueueStrategy.allocate Exception. allocateMessageQueueStrategyName={}", strategy.getName(),
e);
return;
}
Set<MessageQueue> allocateResultSet = new HashSet<MessageQueue>();
if (allocateResult != null) {
allocateResultSet.addAll(allocateResult);
}
// 根据最新的队列信息,更新本地
// 如果有队列被移除,停止消费原队列
// 如果有队列新增,新增拉取消息的任务
boolean changed = this.updateProcessQueueTableInRebalance(topic, allocateResultSet, isOrder);
if (changed) {
log.info(
"rebalanced result changed. allocateMessageQueueStrategyName={}, group={}, topic={}, clientId={}, mqAllSize={}, cidAllSize={}, rebalanceResultSize={}, rebalanceResultSet={}",
strategy.getName(), consumerGroup, topic, this.mQClientFactory.getClientId(), mqSet.size(), cidAll.size(),
allocateResultSet.size(), allocateResultSet);
this.messageQueueChanged(topic, mqSet, allocateResultSet);
}
}
break;
}
default:
break;
}
}
AllocateMessageQueueStrategy
分配队列的策略接口,实现类有如下,假设有8个消费队列,3个消费者ABC
AllocateMessageQueueAveragely 默认使用的,分配后A123, B456, C67
AllocateMessageQueueAveragelyByCircle 分配后A147 B258 C36
AllocateMessageQueueConsistentHash 环形一致性hash算法,下节
AllocateMessageQueueByConfig 自定义配置,为每个消费者自定义要订阅的队列
AllocateMessageQueueByMachineRoom 也是自定义配置,每个消费者只负载自定义配置的机房中Broker的队列信息,BrokerName也需要规范命名
AllocateMessageQueueAveragely#allocate 代码如下
updateProcessQueueTableInRebalance
如果有删除的队列,停止消费消息,移除消息队列
如果有新增的队列,新增消息拉取任务
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