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java客户端连接Zookeeper服务器慢

根据百度结果,推测问题可能是,当使用ip创建ZooKeeper对象时,如果host中没有ip到主机名的映射,ZooKeeper创建过程中会调用ZooInetAddress.getHostName()这个方法从网络中获取主机名,这里耗费时间太长所致。通过调试定位到SaslServerPrincipal类的

static String getServerPrincipal(WrapperInetSocketAddress addr, ZKClientConfig clientConfig) {
        String configuredServerPrincipal = clientConfig.getProperty(ZKClientConfig.ZOOKEEPER_SERVER_PRINCIPAL);
        if (configuredServerPrincipal != null) {
            // If server principal is already configured then return it
            return configuredServerPrincipal;
        }
        String principalUserName = clientConfig.getProperty(
            ZKClientConfig.ZK_SASL_CLIENT_USERNAME,
            ZKClientConfig.ZK_SASL_CLIENT_USERNAME_DEFAULT);
        String hostName = addr.getHostName();
        ......

        if (canonicalize) {
            WrapperInetAddress ia = addr.getAddress();
            ......
            String canonicalHostName = ia.getCanonicalHostName();
            //avoid using literal IP address when security check fails
            if (!canonicalHostName.equals(ia.getHostAddress())) {
                hostName = canonicalHostName;
            }

        }
        String serverPrincipal = principalUserName + "/" + hostName;
        return serverPrincipal;
    }

解决耗时长问题 一个方式就是改host文件,添加ip到域名的映射,但查看上述函数可以发现,如果configuredServerPrincipal不为null,则不会执行String hostName = addr.getHostName();也就可以绕过耗时长的问题。

所以在创建ZooKeeper时,传入ZKClientConfig对象,并配置一个属性,代码如下

String connectString="117.76.191.159";
            ZKClientConfig zkClientConfig = new ZKClientConfig();
            zkClientConfig.setProperty(ZKClientConfig.ZOOKEEPER_SERVER_PRINCIPAL,"zookeeper/"+connectString);
            zooKeeper = new ZooKeeper(connectString, timeout, new Watcher() {
                @Override
                public void process(WatchedEvent event) {
                }
            },false,new StaticHostProvider(new ConnectStringParser(connectString).getServerAddresses()),zkClientConfig);

该方法适合单台Zookeeper,多台可能就不行了。

原文  https://segmentfault.com/a/1190000023284915
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