1、rocket发送消息整个过程可以概括为：检查消息->寻找主题路由信息->选择消息队列->发送消息，本文主要解析寻找主题路由信息部分。
2、以rocketMq源码中的示例开始解读，入口是excample模块中的Producer#send()方法
SendResult sendResult = producer.send(msg);
DefaultMQProducerImpl#sendDefaultImpl方法
Validators.checkMessage(msg, this.defaultMQProducer);
final long invokeID = random.nextLong();
long beginTimestampFirst = System.currentTimeMillis();
long beginTimestampPrev = beginTimestampFirst;
long endTimestamp = beginTimestampFirst;
TopicPublishInfo topicPublishInfo =
#寻找主题路由信息入口，如果寻找不到路由信息，直接抛出异常信息
this.tryToFindTopicPublishInfo(msg.getTopic());
if (topicPublishInfo != null && topicPublishInfo.ok()) {
boolean callTimeout = false;
MessageQueue mq = null;
DefaultMQProducerImpl#tryToFindTopicPublishInfo方法,第一次发送消息时，先从缓存中获取路由信息，如果没有获取到，则从NameServer查找主题信息，如果获取则返回，并且将主题信息放入缓存，如果还未获取到则从NameServer查询默认的主题信息
private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) {
TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic);
if (null == topicPublishInfo || !topicPublishInfo.ok()) {
this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo());
this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic);
topicPublishInfo = this.topicPublishInfoTable.get(topic);
}
if (topicPublishInfo.isHaveTopicRouterInfo() || topicPublishInfo.ok()) {
return topicPublishInfo;
} else {
this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer);
topicPublishInfo = this.topicPublishInfoTable.get(topic);
return topicPublishInfo;
}
}
MQClientInstance#updateTopicRouteInfoFromNameServer方法从NameServer查询主题信息
public boolean updateTopicRouteInfoFromNameServer(final String topic) {
return updateTopicRouteInfoFromNameServer(topic, false, null);
}
public boolean updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault,
DefaultMQProducer defaultMQProducer) {
try {
if (this.lockNamesrv.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
try {
TopicRouteData topicRouteData;
#获取默认主题
if (isDefault && defaultMQProducer != null) {
topicRouteData = this.mQClientAPIImpl.getDefaultTopicRouteInfoFromNameServer(defaultMQProducer.getCreateTopicKey(),
1000 * 3);
if (topicRouteData != null) {
for (QueueData data : topicRouteData.getQueueDatas()) {
int queueNums = Math.min(defaultMQProducer.getDefaultTopicQueueNums(), data.getReadQueueNums());
data.setReadQueueNums(queueNums);
data.setWriteQueueNums(queueNums);
}
}
} else {
#从NameSever获取指定的主题路由信息，底层使用Netty
topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3);
}
if (topicRouteData != null) {
#因为之前在DefaultMQProducerImpl中已经缓存了主题路由信息，包括空的主题路由信息，因此这里需要检查是否要更新
TopicRouteData old = this.topicRouteTable.get(topic);
#比较时是将两个目标对象深度克隆后进行比对，防止影响原来的目标对象
boolean changed = topicRouteDataIsChange(old, topicRouteData);
if (!changed) {
changed = this.isNeedUpdateTopicRouteInfo(topic);
} else {
log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData);
}
#如果需要更新，这更新DefaultMQProducerImpl
if (changed) {
TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();
#更新topic的broker地址信息
for (BrokerData bd : topicRouteData.getBrokerDatas()) {
this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs());
}
// Update Pub info 更新DefaultMQProducerImpl中的topicPublishInfoTable缓存信息
{
TopicPublishInfo publishInfo = topicRouteData2TopicPublishInfo(topic, topicRouteData);
publishInfo.setHaveTopicRouterInfo(true);
Iterator> it = this.producerTable.entrySet().iterator();
while (it.hasNext()) {
Entry entry = it.next();
MQProducerInner impl = entry.getValue();
if (impl != null) {
impl.updateTopicPublishInfo(topic, publishInfo);
}
}
}
// Update sub info更新消费者信息
{
Set subscribeInfo = topicRouteData2TopicSubscribeInfo(topic, topicRouteData);
Iterator> it = this.consumerTable.entrySet().iterator();
while (it.hasNext()) {
Entry entry = it.next();
MQConsumerInner impl = entry.getValue();
if (impl != null) {
impl.updateTopicSubscribeInfo(topic, subscribeInfo);
}
}
}
log.info("topicRouteTable.put. Topic = {}, TopicRouteData[{}]", topic, cloneTopicRouteData);
#将原始的主题路由信息放入缓存
this.topicRouteTable.put(topic, cloneTopicRouteData);
return true;
}
} else {
log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}", topic);
}
} catch (MQClientException e) {
if (!topic.startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) {
log.warn("updateTopicRouteInfoFromNameServer Exception", e);
}
} catch (RemotingException e) {
log.error("updateTopicRouteInfoFromNameServer Exception", e);
throw new IllegalStateException(e);
} finally {
this.lockNamesrv.unlock();
}
} else {
log.warn("updateTopicRouteInfoFromNameServer tryLock timeout {}ms", LOCK_TIMEOUT_MILLIS);
}
} catch (InterruptedException e) {
log.warn("updateTopicRouteInfoFromNameServer Exception", e);
}
return false;
}
MQClientInstance#topicRouteData2TopicPublishInfo方法从TopicRouteData路由信息中获取主题发布相关信息
public static TopicPublishInfo topicRouteData2TopicPublishInfo(final String topic, final TopicRouteData route) {
TopicPublishInfo info = new TopicPublishInfo();
info.setTopicRouteData(route);
#设置有序broker信息list
if (route.getOrderTopicConf() != null && route.getOrderTopicConf().length() > 0) {
String[] brokers = route.getOrderTopicConf().split(";");
for (String broker : brokers) {
String[] item = broker.split(":");
int nums = Integer.parseInt(item[1]);
for (int i = 0; i < nums; i++) {
MessageQueue mq = new MessageQueue(topic, item[0], i);
info.getMessageQueueList().add(mq);
}
}
info.setOrderTopic(true);
} else {
List qds = route.getQueueDatas();
Collections.sort(qds);
for (QueueData qd : qds) {
#只获取有写权限的队列
if (PermName.isWriteable(qd.getPerm())) {
BrokerData brokerData = null;
for (BrokerData bd : route.getBrokerDatas()) {
if (bd.getBrokerName().equals(qd.getBrokerName())) {
brokerData = bd;
break;
}
}
if (null == brokerData) {
continue;
}
#只使用master节点
if (!brokerData.getBrokerAddrs().containsKey(MixAll.MASTER_ID)) {
continue;
}
for (int i = 0; i < qd.getWriteQueueNums(); i++) {
MessageQueue mq = new MessageQueue(topic, qd.getBrokerName(), i);
info.getMessageQueueList().add(mq);
}
}
}
info.setOrderTopic(false);
}
return info;
}
具体请求NameServer的主题路由信息省略，到此，第一次发送消息获取主题路由信息就已完成。