开篇

这个系列主要用以分析mqadmin常见的比较核心的几个命令，主要包括订阅分组和topic的创建和删除、Topic的权限变更、MQAdmin的启动过程。
这篇文章主要是用来分析MQAdmin的启动过程，核心在于namesrv地址的传递以及对应的通信Channel的创建。

MQAdmin启动过后

MQAdmin的启动过程核心逻辑如下

注册各类mqadmin对应的命令和处理函数。
通过System.setProperty(MixAll.NAMESRV_ADDR_PROPERTY, namesrvAddr)在当前执行环境中保存rocketmq集群的namesrv地址，所有命令执行都需要namesrv地址。
MQAdmin启动过程中创建DefaultMQAdminExt对象过程中会通过System.getProperty方法获取namesrv的地址创建Channel对象。

MQAdminStartup

public class MQAdminStartup {
    protected static List<SubCommand> subCommandList = new ArrayList<SubCommand>();

    private static String rocketmqHome = System.getProperty(MixAll.ROCKETMQ_HOME_PROPERTY,
        System.getenv(MixAll.ROCKETMQ_HOME_ENV));

    public static void main(String[] args) {
        main0(args, null);
    }

    public static void main0(String[] args, RPCHook rpcHook) {
        System.setProperty(RemotingCommand.REMOTING_VERSION_KEY, Integer.toString(MQVersion.CURRENT_VERSION));
        // 注册所有的命令行
        initCommand();

        try {
            initLogback();
            switch (args.length) {
                case 0:
                    printHelp();
                    break;
                case 2:
                    if (args[0].equals("help")) {
                        SubCommand cmd = findSubCommand(args[1]);
                        if (cmd != null) {
                            Options options = ServerUtil.buildCommandlineOptions(new Options());
                            options = cmd.buildCommandlineOptions(options);
                            if (options != null) {
                                ServerUtil.printCommandLineHelp("mqadmin " + cmd.commandName(), options);
                            }
                        } else {
                            System.out.printf("The sub command %s not exist.%n", args[1]);
                        }
                        break;
                    }
                case 1:
                default:
                    SubCommand cmd = findSubCommand(args[0]);
                    if (cmd != null) {
                        String[] subargs = parseSubArgs(args);

                        Options options = ServerUtil.buildCommandlineOptions(new Options());
                        final CommandLine commandLine =
                            ServerUtil.parseCmdLine("mqadmin " + cmd.commandName(), subargs, cmd.buildCommandlineOptions(options),
                                new PosixParser());
                        if (null == commandLine) {
                            return;
                        }
                        // mqadmin启动的时候通过-n 参数指定namesrvAddr
                        // 启动的时候会在系统变量中写入"rocketmq.namesrv.addr"
                        if (commandLine.hasOption('n')) {
                            String namesrvAddr = commandLine.getOptionValue('n');
                            System.setProperty(MixAll.NAMESRV_ADDR_PROPERTY, namesrvAddr);
                        }

                        cmd.execute(commandLine, options, AclUtils.getAclRPCHook(rocketmqHome + MixAll.ACL_CONF_TOOLS_FILE));
                    } else {
                        System.out.printf("The sub command %s not exist.%n", args[0]);
                    }
                    break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 注册各类mqadmin对应的命令和处理函数
    public static void initCommand() {
        initCommand(new UpdateTopicSubCommand());
        initCommand(new DeleteTopicSubCommand());
        initCommand(new UpdateSubGroupSubCommand());
        initCommand(new DeleteSubscriptionGroupCommand());
        initCommand(new UpdateBrokerConfigSubCommand());
        initCommand(new UpdateTopicPermSubCommand());
    }
}

注册各类mqadmin对应的命令和处理函数。
System.setProperty(MixAll.NAMESRV_ADDR_PROPERTY, namesrvAddr)启动的时候会在系统变量中写入"rocketmq.namesrv.addr"。

DefaultMQAdminExt

public class DefaultMQAdminExt extends ClientConfig implements MQAdminExt {
    private final DefaultMQAdminExtImpl defaultMQAdminExtImpl;
    private String adminExtGroup = "admin_ext_group";
    private String createTopicKey = MixAll.AUTO_CREATE_TOPIC_KEY_TOPIC;
    private long timeoutMillis = 5000;
    // 构造函数初始化DefaultMQAdminExtImpl对象
    public DefaultMQAdminExt(RPCHook rpcHook) {
        this.defaultMQAdminExtImpl = new DefaultMQAdminExtImpl(this, rpcHook, timeoutMillis);
    }
}


public class ClientConfig {
    public static final String SEND_MESSAGE_WITH_VIP_CHANNEL_PROPERTY = "com.rocketmq.sendMessageWithVIPChannel";
    // ClientConfig的namesrvAddr通过NameServerAddressUtils.getNameServerAddresses()获取
    private String namesrvAddr = NameServerAddressUtils.getNameServerAddresses();
    private String clientIP = RemotingUtil.getLocalAddress();
    private String instanceName = System.getProperty("rocketmq.client.name", "DEFAULT");
    private int clientCallbackExecutorThreads = Runtime.getRuntime().availableProcessors();
    protected String namespace;
    protected AccessChannel accessChannel = AccessChannel.LOCAL;
}


public class NameServerAddressUtils {
    public static final String INSTANCE_PREFIX = "MQ_INST_";
    public static final String INSTANCE_REGEX = INSTANCE_PREFIX + "\\w+_\\w+";
    public static final String ENDPOINT_PREFIX = "http://";
    public static final Pattern NAMESRV_ENDPOINT_PATTERN = Pattern.compile("^" + ENDPOINT_PREFIX + ".*");
    public static final Pattern INST_ENDPOINT_PATTERN = Pattern.compile("^" + ENDPOINT_PREFIX + INSTANCE_REGEX + "\\..*");
    // 负责通过System.getProperty获取namesrv的地址
    public static String getNameServerAddresses() {
        // NAMESRV_ADDR_PROPERTY = "rocketmq.namesrv.addr";
        return System.getProperty(MixAll.NAMESRV_ADDR_PROPERTY, System.getenv(MixAll.NAMESRV_ADDR_ENV));
    }
}

DefaultMQAdminExt的父类ClientConfig的namesrvAddr是从System.getProperty("rocketmq.namesrv.addr")获取的namesrvAddr地址。
创建DefaultMQAdminExtImpl的对象过程中会把DefaultMQAdminExt当作参数传递，该参数同时是ClientConfig对象。
ClientConfig的对象包含namesrv地址信息。

DefaultMQAdminExtImpl

public class DefaultMQAdminExtImpl implements MQAdminExt, MQAdminExtInner {

    @Override
    public void start() throws MQClientException {
        switch (this.serviceState) {
            case CREATE_JUST:
                this.serviceState = ServiceState.START_FAILED;

                this.defaultMQAdminExt.changeInstanceNameToPID();
                // getOrCreateMQClientInstance会创建mqClientInstance
                this.mqClientInstance = MQClientManager.getInstance().getOrCreateMQClientInstance(this.defaultMQAdminExt, rpcHook);
    
                this.serviceState = ServiceState.RUNNING;
                break;
            case RUNNING:
            case START_FAILED:
            case SHUTDOWN_ALREADY:
                throw new MQClientException("The AdminExt service state not OK, maybe started once, "
                    + this.serviceState
                    + FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK), null);
            default:
                break;
        }
    }
}

DefaultMQAdminExtImpl内部通过MQClientManager创建mqClientInstance对象。

MQClientManager

public class MQClientManager {

    private final static InternalLogger log = ClientLogger.getLog();
    private static MQClientManager instance = new MQClientManager();
    private AtomicInteger factoryIndexGenerator = new AtomicInteger();
    private ConcurrentMap<String/* clientId */, MQClientInstance> factoryTable =
        new ConcurrentHashMap<String, MQClientInstance>();

    public MQClientInstance getOrCreateMQClientInstance(final ClientConfig clientConfig, RPCHook rpcHook) {
        String clientId = clientConfig.buildMQClientId();
        MQClientInstance instance = this.factoryTable.get(clientId);
        if (null == instance) {
            // 通过ClientConfig创建MQClientInstance对象
            instance =
                new MQClientInstance(clientConfig.cloneClientConfig(),
                    this.factoryIndexGenerator.getAndIncrement(), clientId, rpcHook);
            MQClientInstance prev = this.factoryTable.putIfAbsent(clientId, instance);
            if (prev != null) {
                instance = prev;
                log.warn("Returned Previous MQClientInstance for clientId:[{}]", clientId);
            } else {
                log.info("Created new MQClientInstance for clientId:[{}]", clientId);
            }
        }

        return instance;
    }
}

MQClientManager内部创建MQClientInstance对象。

MQClientInstance

public class MQClientInstance {

    public MQClientInstance(ClientConfig clientConfig, int instanceIndex, String clientId, RPCHook rpcHook) {
        this.clientConfig = clientConfig;
        this.instanceIndex = instanceIndex;
        this.nettyClientConfig = new NettyClientConfig();
        this.nettyClientConfig.setClientCallbackExecutorThreads(clientConfig.getClientCallbackExecutorThreads());
        this.nettyClientConfig.setUseTLS(clientConfig.isUseTLS());
        this.clientRemotingProcessor = new ClientRemotingProcessor(this);
        this.mQClientAPIImpl = new MQClientAPIImpl(this.nettyClientConfig, this.clientRemotingProcessor, rpcHook, clientConfig);

        // clientConfig.getNamesrvAddr() 在这里不为空
        if (this.clientConfig.getNamesrvAddr() != null) {
            // mQClientAPIImpl的updateNameServerAddressList更新namesrv地址
            this.mQClientAPIImpl.updateNameServerAddressList(this.clientConfig.getNamesrvAddr());
            log.info("user specified name server address: {}", this.clientConfig.getNamesrvAddr());
        }
}

clientConfig.getNamesrvAddr()不为空，会更新mQClientAPIImpl的namesrv的地址。

MQClientAPIImpl

public class MQClientAPIImpl {

    private final static InternalLogger log = ClientLogger.getLog();
    private static boolean sendSmartMsg =
        Boolean.parseBoolean(System.getProperty("org.apache.rocketmq.client.sendSmartMsg", "true"));

    static {
        System.setProperty(RemotingCommand.REMOTING_VERSION_KEY, Integer.toString(MQVersion.CURRENT_VERSION));
    }

    private final RemotingClient remotingClient;
    private final TopAddressing topAddressing;
    private final ClientRemotingProcessor clientRemotingProcessor;
    private String nameSrvAddr = null;
    private ClientConfig clientConfig;

    public MQClientAPIImpl(final NettyClientConfig nettyClientConfig,
        final ClientRemotingProcessor clientRemotingProcessor,
        RPCHook rpcHook, final ClientConfig clientConfig) {
        this.clientConfig = clientConfig;
        topAddressing = new TopAddressing(MixAll.getWSAddr(), clientConfig.getUnitName());
        this.remotingClient = new NettyRemotingClient(nettyClientConfig, null);
        this.clientRemotingProcessor = clientRemotingProcessor;
    }

    public void updateNameServerAddressList(final String addrs) {
        String[] addrArray = addrs.split(";");
        List<String> list = Arrays.asList(addrArray);
        // 更新remotingClient的namesrv的地址
        this.remotingClient.updateNameServerAddressList(list);
    }
}

updateNameServerAddressList会更新remotingClient的namesrv的地址。

NettyRemotingClient

public class NettyRemotingClient extends NettyRemotingAbstract implements RemotingClient {
    // 负责保存namesrv的地址
    private final AtomicReference<List<String>> namesrvAddrList = new AtomicReference<List<String>>();

    public void updateNameServerAddressList(List<String> addrs) {
        List<String> old = this.namesrvAddrList.get();
        boolean update = false;

        if (!addrs.isEmpty()) {
            if (null == old) {
                update = true;
            } else if (addrs.size() != old.size()) {
                update = true;
            } else {
                for (int i = 0; i < addrs.size() && !update; i++) {
                    if (!old.contains(addrs.get(i))) {
                        update = true;
                    }
                }
            }

            if (update) {
                Collections.shuffle(addrs);
                log.info("name server address updated. NEW : {} , OLD: {}", addrs, old);
                this.namesrvAddrList.set(addrs);
            }
        }
    }

    private Channel getAndCreateNameserverChannel() throws RemotingConnectException, InterruptedException {
        String addr = this.namesrvAddrChoosed.get();
        if (addr != null) {
            ChannelWrapper cw = this.channelTables.get(addr);
            if (cw != null && cw.isOK()) {
                return cw.getChannel();
            }
        }
        // 创建NameserverChannel的时候会取namesrv地址
        final List<String> addrList = this.namesrvAddrList.get();
        if (this.lockNamesrvChannel.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
            try {
                addr = this.namesrvAddrChoosed.get();
                if (addr != null) {
                    ChannelWrapper cw = this.channelTables.get(addr);
                    if (cw != null && cw.isOK()) {
                        return cw.getChannel();
                    }
                }

                if (addrList != null && !addrList.isEmpty()) {
                    for (int i = 0; i < addrList.size(); i++) {
                        int index = this.namesrvIndex.incrementAndGet();
                        index = Math.abs(index);
                        index = index % addrList.size();
                        String newAddr = addrList.get(index);
                        this.namesrvAddrChoosed.set(newAddr);
                        Channel channelNew = this.createChannel(newAddr);
                        if (channelNew != null) {
                            return channelNew;
                        }
                    }
                    throw new RemotingConnectException(addrList.toString());
                }
            } finally {
                this.lockNamesrvChannel.unlock();
            }
        } 

        return null;
    }
}

NettyRemotingClient的namesrvAddrList保存namesrv的地址。
NettyRemotingClient的getAndCreateNameserverChannel方法获取namesrvAddrList的地址创建namesrv的通信channel。