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开篇先上一张RocketMQ官方的经典架构图，如下图所示：
Rocketmq是开源的消息中间件,主要是四部分由NameServer,Producer,Broker,Consumer构成
1)NameServer:类似于注册中心,负责Topic和路由信息的管理
2)Producer:生产者,消息的发送端
3)Broker:消息存储,以及消息转发
4)Consumer:消费者,消费消息
NameServer:是一个近乎无状态的节点,由上面的架构图可知,每台NameServer相互独立,Broker与每台NameServer保持长连接通信。还是老规矩,怎么找NameServer的入口,就看他的启动脚本就完事了NameServer的启动脚本位于源码rocketmq/distribution/bin/mqnamesrv里由脚本可知org.apache.rocketmq.namesrv.NamesrvStartup是启动类,一起看下源码，以下源码解析均为重要方法选择性解析，全面解析的话时间不是很充足。
public static void main(String[] args) {
main0(args);
}
public static NamesrvController main0(String[] args) {
try {
NamesrvController controller = createNamesrvController(args);
start(controller);
String tip = "The Name Server boot success. serializeType=" + RemotingCommand.getSerializeTypeConfigInThisServer();
log.info(tip);
System.out.printf("%s%n", tip);
return controller;
} catch (Throwable e) {
e.printStackTrace();
System.exit(-1);
}
return null;
}
1)启动类可以看出NamesrvController是整个NameServer的核心控制
看下NamesrvController的类图
//代码
// namerServer 配置信息
private final NamesrvConfig namesrvConfig;
// netty配置信息
private final NettyServerConfig nettyServerConfig;
// 调度任务
private final ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactoryImpl( "NSScheduledThread"));
// 读取或变更NameServer的属性 加载NamerServer的属性到内存
private final KVConfigManager kvConfigManager;
// 记录Broker,Topic信息以及关联
private final RouteInfoManager routeInfoManager;
// netty server端
private RemotingServer remotingServer;
// 处理netty事件接口(连接,关闭,异常,心跳事件)
private BrokerHousekeepingService brokerHousekeepingService;
// 业务线程池private ExecutorService remotingExecutor;全局配置类 数据版本号,存储base路径等等
private Configuration configuration;
// 监听证书文件是否有有变化
private FileWatchService fileWatchService;
2)NamesrvController属性
NamesrvConfig:主要是NameServer的一些配置kvConfigPath,rocketmqHome等
如下NettyServerConfig(netty相关配置)源码
public class NettyServerConfig implements Cloneable {
//Server端端口
private int listenPort = 8888;
//业务线程池个数
private int serverWorkerThreads = 8;
//默认业务线程池，采用fixed类型
private int serverCallbackExecutorThreads = 0;
//Netty I/O线程数处理Selector读写事件线程数
private int serverSelectorThreads = 3;
//用于限流
private int serverOnewaySemaphoreValue = 256;
//异步调用限流
private int serverAsyncSemaphoreValue = 64;
//channel的空闲时间 idleHandler实现
private int serverChannelMaxIdleTimeSeconds = 120;
//socket 发送缓冲区大小 默认 65535
private int serverSocketSndBufSize = NettySystemConfig.socketSndbufSize;
//socket 接收缓冲区大小 65535
private int serverSocketRcvBufSize = NettySystemConfig.socketRcvbufSize;
//是否使用PooledByteBufd
private boolean serverPooledByteBufAllocatorEnable = true;
}
3)scheduledExecutorService，定时任务线程池的配置详情
public class NettyServerConfig implements Cloneable {
//Server端端口
private int listenPort = 8888;
//业务线程池个数
private int serverWorkerThreads = 8;
//默认业务线程池，采用fixed类型
private int serverCallbackExecutorThreads = 0;
//Netty I/O线程数处理Selector读写事件线程数
private int serverSelectorThreads = 3;
//用于限流
private int serverOnewaySemaphoreValue = 256;
//异步调用限流
private int serverAsyncSemaphoreValue = 64;
//channel的空闲时间 idleHandler实现
private int serverChannelMaxIdleTimeSeconds = 120;
//socket 发送缓冲区大小 默认 65535
private int serverSocketSndBufSize = NettySystemConfig.socketSndbufSize;
//socket 接收缓冲区大小 65535
private int serverSocketRcvBufSize = NettySystemConfig.socketRcvbufSize;
//是否使用PooledByteBufd
private boolean serverPooledByteBufAllocatorEnable = true;
}
4)调度器主要执行两个任务，10s一次检测channel是否最后一个的活跃事件，是否大于配置的超时时间,看下任务代码,其实就是类似于心跳检测,在Broker也有调度线程10s一次调用BrokerController.registerBrokerAll()方法实现路由注册等发送QUERY_DATA_VERSION事件去更新LastUpdateTimestamp字段实现心跳检测的功能，源码如下：
//扫描不活跃的的broker 信息
public void scanNotActiveBroker() {
//获取所有live的brokerinfo
Iterator<Entry<String, BrokerLiveInfo>> it = this.brokerLiveTable.entrySet().iterator();
while (it.hasNext()) {
Entry<String, BrokerLiveInfo> next = it.next();
//获取最新的一次updateTime时间
long last = next.getValue().getLastUpdateTimestamp();
//判断是否超时
if ((last + BROKER_CHANNEL_EXPIRED_TIME) < System.currentTimeMillis()) {
//超时的话,关闭broker的channel
RemotingUtil.closeChannel(next.getValue().getChannel());
it.remove();
log.warn("The broker channel expired, {} {}ms", next.getKey(), BROKER_CHANNEL_EXPIRED_TIME);
//移除BrokerLiveInfo,以及对应的Topic信息
this.onChannelDestroy(next.getKey(), next.getValue().getChannel());
}
}
}
5)RouteInfoManager(NameServer存储的核心信息)
//以下为具体属性
//NameServer 与broker的空闲时间 查过两分钟没有收到心跳 关闭该链接
private final static long BROKER_CHANNEL_EXPIRED_TIME = 1000 * 60 * 2;
//读写锁
private final ReadWriteLock lock = new ReentrantReadWriteLock();
//topic 与队列的关系 以及topic 分布在哪些Broker上 每个broker存在该topic的个数
private final HashMap<String/* topic */, List<QueueData>> topicQueueTable;
// 所有的broker信息 brokerName 为key
private final HashMap<String/* brokerName */, BrokerData> brokerAddrTable;
//broker集群信息，每个集群包含哪些Broker,key为集群名称
private final HashMap<String/* clusterName */, Set<String/* brokerName */>> clusterAddrTable;
// 当前存活的Broker,该信息不是实时的，NameServer每10S扫描一次所有的broker,根据心跳包的时间得知broker的状态
private final HashMap<String/* brokerAddr */, BrokerLiveInfo> brokerLiveTable;
//过滤的broker
private final HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;
6)核心属性实体(QueueData队列属性)
//写队列:producer可以发送的queue的个数
//读队列:consumer可以拉取的队列的个数
public class QueueData implements Comparable<QueueData> {
//borker name
private String brokerName;
//写队列的个数
private int readQueueNums;
//读队列的个数
private int writeQueueNums;
//权限
private int perm;
//同步复制 还是异步复制
private int topicSynFlag;
}
7)BrokerData(Broker属性)
public class BrokerData implements Comparable<BrokerData> {
//集群名称,节点信息,分布在哪个节点信息
private String cluster;
//brokerName
private String brokerName;
//broker 对应的IP:Port,brokerId=0表示Master,大于0表示Slave。
private HashMap<Long/* brokerId */, String/* broker address */> brokerAddrs;
//随机数,随机获取一个broker的地址
private final Random random = new Random();
}
8)BrokerLiveInfo(活跃的Broker)
class BrokerLiveInfo {
//时间戳用于判断Broker是否存活
private long lastUpdateTimestamp;
private DataVersion dataVersion;
//socket通信
private Channel channel;
//ha 地址
private String haServerAddr;
}
9)TopicConfig(Topic配置信息)
public class TopicConfig {
private static final String SEPARATOR = " ";
//默认读队列数量
public static int defaultReadQueueNums = 16;
// 默认写队列数量
public static int defaultWriteQueueNums = 16;
//topic 主题名称
private String topicName;
//readQueue数量
private int readQueueNums = defaultReadQueueNums;
//write Queue数量
private int writeQueueNums = defaultWriteQueueNums;
//读取权限
private int perm = PermName.PERM_READ | PermName.PERM_WRITE;
//主题过滤方式
private TopicFilterType topicFilterType = TopicFilterType.SINGLE_TAG;
//系统标志,比如事务,延时等
private int topicSysFlag = 0;
//是否顺序消费
private boolean order = false;
}
10)TopicRouteData(Topic路由信息)
public class TopicRouteData extends RemotingSerializable {
//是否顺序消息
private String orderTopicConf;
//topic分布在哪些Broker上,以及读写队列的个数
private List<QueueData> queueDatas;
// topic分布的Broker信息
private List<BrokerData> brokerDatas;
//需要过滤的address
private HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;
}