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本篇文章给大家分享的是有关consumer数量变化会怎样，小编觉得挺实用的，因此分享给大家学习，希望大家阅读完这篇文章后可以有所收获，话不多说，跟着小编一起来看看吧。
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ConsumerManager public boolean registerConsumer(final String group, final ClientChannelInfo clientChannelInfo, ConsumeType consumeType, MessageModel messageModel, ConsumeFromWhere consumeFromWhere, final SetsubList, boolean isNotifyConsumerIdsChangedEnable) { ConsumerGroupInfo consumerGroupInfo = this.consumerTable.get(group); if (null == consumerGroupInfo) { ConsumerGroupInfo tmp = new ConsumerGroupInfo(group, consumeType, messageModel, consumeFromWhere); ConsumerGroupInfo prev = this.consumerTable.putIfAbsent(group, tmp); consumerGroupInfo = prev != null ? prev : tmp; } boolean r1 = consumerGroupInfo.updateChannel(clientChannelInfo, consumeType, messageModel, consumeFromWhere); boolean r2 = consumerGroupInfo.updateSubscription(subList); if (r1 || r2) { if (isNotifyConsumerIdsChangedEnable) { //通知同组内的其他consumer this.consumerIdsChangeListener.handle(ConsumerGroupEvent.CHANGE, group, consumerGroupInfo.getAllChannel()); } } this.consumerIdsChangeListener.handle(ConsumerGroupEvent.REGISTER, group, subList); return r1 || r2; } public void unregisterConsumer(final String group, final ClientChannelInfo clientChannelInfo, boolean isNotifyConsumerIdsChangedEnable) { ConsumerGroupInfo consumerGroupInfo = this.consumerTable.get(group); if (null != consumerGroupInfo) { consumerGroupInfo.unregisterChannel(clientChannelInfo); if (consumerGroupInfo.getChannelInfoTable().isEmpty()) { ConsumerGroupInfo remove = this.consumerTable.remove(group); if (remove != null) { log.info("unregister consumer ok, no any connection, and remove consumer group, {}", group); this.consumerIdsChangeListener.handle(ConsumerGroupEvent.UNREGISTER, group); } } if (isNotifyConsumerIdsChangedEnable) { //单向通知channel this.consumerIdsChangeListener.handle(ConsumerGroupEvent.CHANGE, group, consumerGroupInfo.getAllChannel()); } } }
DefaultConsumerIdsChangeListener
@Override
public void handle(ConsumerGroupEvent event, String group, Object... args) {
case CHANGE:
if (args == null || args.length < 1) {
return;
}
List channels = (List) args[0];
if (channels != null && brokerController.getBrokerConfig().isNotifyConsumerIdsChangedEnable()) {
//对组内的其他consumer的channel连接发送单向通知（不管对方有木有收到）
for (Channel chl : channels) {
this.brokerController.getBroker2Client().notifyConsumerIdsChanged(chl, group);
}
}
break;
} Broker2Client
public void notifyConsumerIdsChanged(
final Channel channel,
final String consumerGroup) {
if (null == consumerGroup) {
log.error("notifyConsumerIdsChanged consumerGroup is null");
return;
}
NotifyConsumerIdsChangedRequestHeader requestHeader = new NotifyConsumerIdsChangedRequestHeader();
requestHeader.setConsumerGroup(consumerGroup);
RemotingCommand request =
RemotingCommand.createRequestCommand(RequestCode.NOTIFY_CONSUMER_IDS_CHANGED, requestHeader);
try {
this.brokerController.getRemotingServer().invokeOneway(channel, request, 10);
} catch (Exception e) {
//发送异常，只是打印log
log.error("notifyConsumerIdsChanged exception, " + consumerGroup, e.getMessage());
}
}通知channel是单向的，也就是不管对方有没有答复，都认为发送成功了，这样会有两种情况发生:
channel收到消息：收到消息后，channel会触发rebalance，正常逻辑
channel没收到消息：该consumer不会触发rebalance，存在问题！
register：该consumer不知道已经有新的consumer加入，造成同一个mq会有多个consumer进行消费
unregister：该consumer不知道有consumer下线，造成部分mq没有consumer负责消费
我们先看unregister这种情况
在consumer启动时，会同时启动一个RebalanceService线程，这个线程做的事就是每隔20秒主动进行一次rebalance，这样就能把unregister这种影响降低，最多导致该mq的消息会延迟20秒之后才有consumer负责消费
RebalanceService
private static long waitInterval = Long.parseLong(System.getProperty("rocketmq.client.rebalance.waitInterval", "20000"));
@Override
public void run() {
log.info(this.getServiceName() + " service started");
while (!this.isStopped()) {
this.waitForRunning(waitInterval);
this.mqClientFactory.doRebalance();
}
log.info(this.getServiceName() + " service end");
}接下来分析比较大条的Register
同一个mq在同一组内有不同的consumer消费，这种情况在clustering模式下是有大问题的，会造成重复消费，消费进度错误等问题，带着rocketmq应该不至于犯如此低级错误的想法再继续看代码，果然别有洞天
RebalanceImpl
private void rebalanceByTopic(final String topic, final boolean isOrder) {
//rebalance过程
//关键点在这，在上面rebalance完之后， 就能知道自己该负责哪些mq的消费
boolean changed = this.updateProcessQueueTableInRebalance(topic, allocateResultSet, isOrder);
}
private boolean updateProcessQueueTableInRebalance(final String topic, final Set mqSet, final boolean isOrder) {
for (MessageQueue mq : mqSet) {
//如果是新增的mq，会尝试调用远程broker lock mq，获取锁失败，则说明有其他consumer获取了锁，自己应该放弃消费该mq
if (!this.processQueueTable.containsKey(mq)) {
if (isOrder && !this.lock(mq)) {
log.warn("doRebalance, {}, add a new mq failed, {}, because lock failed", consumerGroup, mq);
continue;
}
}
}
} 以上就是consumer数量变化会怎样，小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注创新互联行业资讯频道。
