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一、引言

在分布式系统的消息传递领域，RocketMQ 以其高性能、高可用性和强大的扩展性脱颖而出。ProducerManager 作为 RocketMQ 中的一个关键组件，在消息生产环节发挥着至关重要的作用。它负责管理消息生产者（Producer）的生命周期、配置和操作，为系统的稳定运行和高效消息传递提供了坚实的基础。

二、ProducerManager 的核心功能

2.1 核心属性

//网络连接过期超时时间private static final long CHANNEL_EXPIRED_TIMEOUT = 1000 * 120;//获取可用网络连接重试次数 默认3次private static final int GET_AVAILABLE_CHANNEL_RETRY_COUNT = 3;//生产组-》网络连接-》客户端信息private final ConcurrentHashMap<String /* group name */, ConcurrentHashMap<Channel, ClientChannelInfo>> groupChannelTable =new ConcurrentHashMap<>();//每个生产者网络客户端id到网络连接的映射关系private final ConcurrentHashMap<String, Channel> clientChannelTable = new ConcurrentHashMap<>();//正数计数器private PositiveAtomicCounter positiveAtomicCounter = new PositiveAtomicCounter();

主要数据结构为groupChannelTable，里面进行存放的是key为生产者组的名字，value为ConcurrentHashMap<Channel, ClientChannelInfo>，这个Map中Channel为与客户端通信的channel,value为ClientChannelInfo 是客户端的信息，主要属性为：

// 消费者客户端网络连接信息
public class ClientChannelInfo {private final Channel channel;//消费者客户端网络连接idprivate final String clientId;//编程语言private final LanguageCode language;//版本语言private final int version;//最后更新时间戳private volatile long lastUpdateTimestamp = System.currentTimeMillis();//.....省略代码
}

2.2 核心方法

1. 自动扫描方法，会每隔一段时间进行针对groupChannelTable中的数据进行扫描，将Map中Channel最后更新时间，超过2分钟没有进行更新的连接从groupChannelTable中进行移除。

代码如下：

    /*** 扫描生产者过期的网络连接*/public void scanNotActiveChannel() {for (final Map.Entry<String, ConcurrentHashMap<Channel, ClientChannelInfo>> entry : this.groupChannelTable.entrySet()) {final String group = entry.getKey();final ConcurrentHashMap<Channel, ClientChannelInfo> chlMap = entry.getValue();Iterator<Entry<Channel, ClientChannelInfo>> it = chlMap.entrySet().iterator();while (it.hasNext()) {Entry<Channel, ClientChannelInfo> item = it.next();// final Integer id = item.getKey();final ClientChannelInfo info = item.getValue();long diff = System.currentTimeMillis() - info.getLastUpdateTimestamp();if (diff > CHANNEL_EXPIRED_TIMEOUT) {it.remove();clientChannelTable.remove(info.getClientId());log.warn("SCAN: remove expired channel[{}] from ProducerManager groupChannelTable, producer group name: {}",RemotingHelper.parseChannelRemoteAddr(info.getChannel()), group);RemotingUtil.closeChannel(info.getChannel());}}}}

 2.处理生产者连接关闭的事件

  //处理生产者连接关闭的事件public synchronized void doChannelCloseEvent(final String remoteAddr, final Channel channel) {if (channel != null) {for (final Map.Entry<String, ConcurrentHashMap<Channel, ClientChannelInfo>> entry : this.groupChannelTable.entrySet()) {final String group = entry.getKey();final ConcurrentHashMap<Channel, ClientChannelInfo> clientChannelInfoTable =entry.getValue();final ClientChannelInfo clientChannelInfo =clientChannelInfoTable.remove(channel);if (clientChannelInfo != null) {clientChannelTable.remove(clientChannelInfo.getClientId());log.info("NETTY EVENT: remove channel[{}][{}] from ProducerManager groupChannelTable, producer group: {}",clientChannelInfo.toString(), remoteAddr, group);}}}}

3.生产者的注册与下线

注册方法：

    //注册生产者public synchronized void registerProducer(final String group, final ClientChannelInfo clientChannelInfo) {ClientChannelInfo clientChannelInfoFound = null;ConcurrentHashMap<Channel, ClientChannelInfo> channelTable = this.groupChannelTable.get(group);if (null == channelTable) {channelTable = new ConcurrentHashMap<>();this.groupChannelTable.put(group, channelTable);}clientChannelInfoFound = channelTable.get(clientChannelInfo.getChannel());if (null == clientChannelInfoFound) {channelTable.put(clientChannelInfo.getChannel(), clientChannelInfo);clientChannelTable.put(clientChannelInfo.getClientId(), clientChannelInfo.getChannel());log.info("new producer connected, group: {} channel: {}", group,clientChannelInfo.toString());}if (clientChannelInfoFound != null) {clientChannelInfoFound.setLastUpdateTimestamp(System.currentTimeMillis());}}

下线方法

   //生产者的下线public synchronized void unregisterProducer(final String group, final ClientChannelInfo clientChannelInfo) {ConcurrentHashMap<Channel, ClientChannelInfo> channelTable = this.groupChannelTable.get(group);if (null != channelTable && !channelTable.isEmpty()) {ClientChannelInfo old = channelTable.remove(clientChannelInfo.getChannel());clientChannelTable.remove(clientChannelInfo.getClientId());if (old != null) {log.info("unregister a producer[{}] from groupChannelTable {}", group,clientChannelInfo.toString());}if (channelTable.isEmpty()) {this.groupChannelTable.remove(group);log.info("unregister a producer group[{}] from groupChannelTable", group);}}}

4. 根据生产者的groupId获取可用的连接

//获取当前生产者组可用的连接public Channel getAvailableChannel(String groupId) {if (groupId == null) {return null;}List<Channel> channelList;ConcurrentHashMap<Channel, ClientChannelInfo> channelClientChannelInfoHashMap = groupChannelTable.get(groupId);if (channelClientChannelInfoHashMap != null) {channelList = new ArrayList<>(channelClientChannelInfoHashMap.keySet());} else {log.warn("Check transaction failed, channel table is empty. groupId={}", groupId);return null;}int size = channelList.size();if (0 == size) {log.warn("Channel list is empty. groupId={}", groupId);return null;}Channel lastActiveChannel = null;//轮询算法，依次获取生产者组的每一个生产者的连接地址int index = positiveAtomicCounter.incrementAndGet() % size;Channel channel = channelList.get(index);int count = 0;boolean isOk = channel.isActive() && channel.isWritable();while (count++ < GET_AVAILABLE_CHANNEL_RETRY_COUNT) {if (isOk) {return channel;}if (channel.isActive()) {lastActiveChannel = channel;}index = (++index) % size;channel = channelList.get(index);isOk = channel.isActive() && channel.isWritable();}return lastActiveChannel;}

三、总结

总的来看，ProducerManager主要是通过类中的方法对groupChannelTable集合中的属性进行操作