dubbo注册服务IP解析异常及IP解析源码分析

在使用dubbo注册服务时会遇到IP解析错误导致无法正常访问.
比如: 本机设置的IP为172.16.11.111, 但实际解析出来的是180.20.174.11
这样就导致这个Service永远也无法被访问到, 而调用方一直报错.

当然若发现服务无法访问, 最好先通过dubbo-admin后台排查下注册的服务是否正常.

IP解析异常时的解决方法:

• 绑定hostname+ip

    1. 先查看机器的hostname
    2. 修改hosts文件, 增加hostname 172.16.11.111

• 配置nameserver

    排查机器上配置的nameserver是否有问题, 若存在无用的nameserver则直接删掉

• 在dubbo的配置文件中写死host

    <dubbo:protocol host="172.16.11.111"/>
    或者在每个provider中绑定host
    <dubbo:provider host="172.16.11.111">

最好不要用第三种方式, 限制太多. 而且如果这样做了就不支持集群了.
dubbo的官网也不建议使用这种方式. 请慎用.

dubbo获取IP源码分析

    /**
     * 判断host是否为不可用的本地Host
     */
    public static boolean isInvalidLocalHost(String host) {
        return host == null 
                    || host.length() == 0
                    || host.equalsIgnoreCase("localhost")
                    || host.equals("0.0.0.0")
                    || (LOCAL_IP_PATTERN.matcher(host).matches());
    }

    /**
     * 获取本地Host.
     * 若address == null ? "127.0.0.1" : InetAddress.getHostAddress();
     */
    public static String getLocalHost(){
        InetAddress address = getLocalAddress();
        return address == null ? LOCALHOST : address.getHostAddress();
    }

    private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
        ...
        ...
        //1. 先从ProtocolConfig中取host. 若没有配置则为null
        String host = protocolConfig.getHost();

        //2. 再从ProviderConfig中取host. 若没有配置则为null
        if (provider != null && (host == null || host.length() == 0)) {
            host = provider.getHost();
        }

        boolean anyhost = false;

        //3. 若取出的是本地host, 则继续取host
        if (NetUtils.isInvalidLocalHost(host)) {
            anyhost = true;
            try {
                //4. 通过InetAddress的方式获取Host
                //默认读取本机hosts中hostname对应的IP
                //如: 你在hosts中配置了 leo 172.16.11.111
                //则读取的IP就是172.16.11.111
                host = InetAddress.getLocalHost().getHostAddress();
            } catch (UnknownHostException e) {
                logger.warn(e.getMessage(), e);
            }
            if (NetUtils.isInvalidLocalHost(host)) {
                if (registryURLs != null && registryURLs.size() > 0) {
                    for (URL registryURL : registryURLs) {
                        try {
                            Socket socket = new Socket();
                            try {
                                //5. 通过Socket的方式获取Host
                                //一般解析到这里, 都会获取到正确的本地IP, 除非你有多网卡, 或者有VPN, 导致无法正常解析.
                                SocketAddress addr = new InetSocketAddress(registryURL.getHost(), registryURL.getPort());
                                socket.connect(addr, 1000);
                                host = socket.getLocalAddress().getHostAddress();
                                break;
                            } finally {
                                try {
                                    socket.close();
                                } catch (Throwable e) {}
                            }
                        } catch (Exception e) {
                            logger.warn(e.getMessage(), e);
                        }
                    }
                }

                //6. 遍历本地网卡, 返回第一个合理的Host
                //最后一个大招. 当上述都解析不到时, 则会遍历本地网卡.
                //逐个获取IP, 直到有一个合理的IP为止.
                if (NetUtils.isInvalidLocalHost(host)) {
                    host = NetUtils.getLocalHost();
                }
            }
        }
        ...
    }

    /**
     * 遍历本地网卡，返回第一个合理的IP。
     * @return 本地网卡IP
     */
    public static InetAddress getLocalAddress() {
        if (LOCAL_ADDRESS != null)
            return LOCAL_ADDRESS;
        InetAddress localAddress = getLocalAddress0();
        LOCAL_ADDRESS = localAddress;
        return localAddress;
    }

    /**
     * 遍历本地网卡，返回第一个合理的IP。
     * @return 本地网卡IP
     */
    private static InetAddress getLocalAddress0() {
        InetAddress localAddress = null;
        try {
            localAddress = InetAddress.getLocalHost();
            if (isValidAddress(localAddress)) {
                return localAddress;
            }
        } catch (Throwable e) {
            logger.warn("Failed to retriving ip address, " + e.getMessage(), e);
        }
        try {
            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
            if (interfaces != null) {
                while (interfaces.hasMoreElements()) {
                    try {
                        NetworkInterface network = interfaces.nextElement();
                        Enumeration<InetAddress> addresses = network.getInetAddresses();
                        if (addresses != null) {
                            while (addresses.hasMoreElements()) {
                                try {
                                    InetAddress address = addresses.nextElement();
                                    if (isValidAddress(address)) {
                                        return address;
                                    }
                                } catch (Throwable e) {
                                    logger.warn("Failed to retriving ip address, " + e.getMessage(), e);
                                }
                            }
                        }
                    } catch (Throwable e) {
                        logger.warn("Failed to retriving ip address, " + e.getMessage(), e);
                    }
                }
            }
        } catch (Throwable e) {
            logger.warn("Failed to retriving ip address, " + e.getMessage(), e);
        }
        logger.error("Could not get local host ip address, will use 127.0.0.1 instead.");
        return localAddress;
    }