引言
在上文中我们已经明确了消息发送之前需要进行的一系列准备工作。本文继续进行这部分源码阅读，主要涉及路由信息获取以及故障Broker的延迟助理策略。
- 基本流程
- 总结
一、基本流程
发送消息时需要获取路由信息，在上篇文章中我们知道会从以下方法中即tryToFindTopicPublishInfo()获取。根据待发送消息的中包含的Topic信息尝试从客户端的本地缓存变量—topicPublishInfoTable中进行查找。如果没有则会从NameServer上更新Topic的路由信息。
在MQClientInstance实例的updateTopicRouteInfoFromNameServer方法功能为消息生产者更新和维护路由缓存信息。
public boolean updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault, DefaultMQProducer defaultMQProducer) { try { if (this.lockNamesrv.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) { try { TopicRouteData topicRouteData; // 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 { topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3); } if (topicRouteData != null) { TopicRouteData old = this.topicRouteTable.get(topic); boolean changed = topicRouteDataIsChange(old, topicRouteData); if (!changed) { changed = this.isNeedUpdateTopicRouteInfo(topic); } else { log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData); } if (changed) { TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData(); for (BrokerData bd : topicRouteData.getBrokerDatas()) { this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs()); } // Update Pub info { TopicPublishInfo publishInfo = topicRouteData2TopicPublishInfo(topic, topicRouteData); publishInfo.setHaveTopicRouterInfo(true); Iterator<Entry<String, MQProducerInner>> it = this.producerTable.entrySet().iterator(); while (it.hasNext()) { Entry<String, MQProducerInner> entry = it.next(); MQProducerInner impl = entry.getValue(); if (impl != null) { impl.updateTopicPublishInfo(topic, publishInfo); } } } // Update sub info { Set<MessageQueue> subscribeInfo = topicRouteData2TopicSubscribeInfo(topic, topicRouteData); Iterator<Entry<String, MQConsumerInner>> it = this.consumerTable.entrySet().iterator(); while (it.hasNext()) { Entry<String, MQConsumerInner> entry = it.next(); MQConsumerInner impl = entry.getValue(); if (impl != null) { impl.updateTopicSubscribeInfo(topic, subscribeInfo); } } } log.info("topicRouteTable.put. Topic = {}, TopicRouteData[{}]", topic, cloneTopicRouteData); this.topicRouteTable.put(topic, cloneTopicRouteData); return true; } } else { log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}", topic); } } catch (Exception e) { if (!topic.startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX) && !topic.equals(MixAll.AUTO_CREATE_TOPIC_KEY_TOPIC)) { log.warn("updateTopicRouteInfoFromNameServer Exception", 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; }
public MessageQueue selectOneMessageQueue(final String lastBrokerName) { if (lastBrokerName == null) { return selectOneMessageQueue(); } else { int index = this.sendWhichQueue.getAndIncrement(); for (int i = 0; i < this.messageQueueList.size(); i++) { int pos = Math.abs(index++) % this.messageQueueList.size(); if (pos < 0) pos = 0; MessageQueue mq = this.messageQueueList.get(pos); if (!mq.getBrokerName().equals(lastBrokerName)) { return mq; } } return selectOneMessageQueue(); } }
Broker的故障延迟策略机制在MQFaultStrategy 中进行了定义，最主要的方法是selectOneMessageQueue，大致的处理流程如下所示：
具体的源码分析如下所示：
public class MQFaultStrategy { private final static InternalLogger log = ClientLogger.getLog(); //维护每个Broker发送消息的延迟 private final LatencyFaultTolerance<String> latencyFaultTolerance = new LatencyFaultToleranceImpl(); //发送消息延迟容错开关 private boolean sendLatencyFaultEnable = false; //延迟级别数组 private long[] latencyMax = {50L, 100L, 550L, 1000L, 2000L, 3000L, 15000L}; //不可用时长数组 private long[] notAvailableDuration = {0L, 0L, 30000L, 60000L, 120000L, 180000L, 600000L}; public long[] getNotAvailableDuration() { return notAvailableDuration; } public void setNotAvailableDuration(final long[] notAvailableDuration) { this.notAvailableDuration = notAvailableDuration; } public long[] getLatencyMax() { return latencyMax; } public void setLatencyMax(final long[] latencyMax) { this.latencyMax = latencyMax; } public boolean isSendLatencyFaultEnable() { return sendLatencyFaultEnable; } public void setSendLatencyFaultEnable(final boolean sendLatencyFaultEnable) { this.sendLatencyFaultEnable = sendLatencyFaultEnable; } public MessageQueue selectOneMessageQueue(final TopicPublishInfo tpInfo, final String lastBrokerName) { if (this.sendLatencyFaultEnable) { try { //1.在随机递增取模的基础上，再过滤掉not available的Broker代理;对之前失败的，按一定的时间做退避 int index = tpInfo.getSendWhichQueue().getAndIncrement(); //队列轮询 for (int i = 0; i < tpInfo.getMessageQueueList().size(); i++) { int pos = Math.abs(index++) % tpInfo.getMessageQueueList().size(); if (pos < 0) pos = 0; //获取一个消息队列 MessageQueue mq = tpInfo.getMessageQueueList().get(pos); //验证消息队列是否可用 if (latencyFaultTolerance.isAvailable(mq.getBrokerName())) { if (null == lastBrokerName || mq.getBrokerName().equals(lastBrokerName)) return mq; } } final String notBestBroker = latencyFaultTolerance.pickOneAtLeast(); int writeQueueNums = tpInfo.getQueueIdByBroker(notBestBroker); if (writeQueueNums > 0) { final MessageQueue mq = tpInfo.selectOneMessageQueue(); if (notBestBroker != null) { mq.setBrokerName(notBestBroker); mq.setQueueId(tpInfo.getSendWhichQueue().getAndIncrement() % writeQueueNums); } return mq; } else { latencyFaultTolerance.remove(notBestBroker); } } catch (Exception e) { log.error("Error occurred when selecting message queue", e); } return tpInfo.selectOneMessageQueue(); } //2.采用随机递增取模的方式选择一个队列（MessageQueue）来发送消息 return tpInfo.selectOneMessageQueue(lastBrokerName); } public void updateFaultItem(final String brokerName, final long currentLatency, boolean isolation) { if (this.sendLatencyFaultEnable) { long duration = computeNotAvailableDuration(isolation ? 30000 : currentLatency); this.latencyFaultTolerance.updateFaultItem(brokerName, currentLatency, duration); } } private long computeNotAvailableDuration(final long currentLatency) { for (int i = latencyMax.length - 1; i >= 0; i--) { if (currentLatency >= latencyMax[i]) return this.notAvailableDuration[i]; } return 0; } }
二、总结
本文主要介绍了，消息发送之前RocketMQ进行的Broker故障延迟选择策略。它是一种对于故障Broker的一种调度策略，可以规避对于故障Broker的使用。在下文中，我们将正式进行消息发送的源码阅读以及分析。
