Caused by: com.alibaba.dubbo.remoting.TimeoutException: Waiting server-side response timeout by scan timer. start time: 2016-07-20 16:27:34.873, end time: 2016-07-20 16:27:39.895, client elapsed: 0 ms

方案一：

重启dubbo连接 zookeeper

方案二：

经压测，greys跟踪得知，是dubbo的monitor的问题。主要超时的方法是dubbo的getIP方法，monitor每次收集数据的时候都要根据域名获取zk的IP，这一步耗时很长。

    public String getIp() {
        if (ip == null) {
            ip = NetUtils.getIpByHost(host);
        }
        return ip;
    }

现在改了dubbo的源码，monitor每次收集数据的时候不获取zk的ip，直接用域名。增加如下方法，

    public String toServiceString(boolean useIP){
        return buildString(true, false, useIP, true);
    }

修改AbstractMonitorFactory的方法

    public Monitor getMonitor(URL url) {
        url = url.setPath(MonitorService.class.getName()).addParameter(Constants.INTERFACE_KEY, MonitorService.class.getName());
        String key = url.toServiceString(false);
        LOCK.lock();
        try {
            Monitor monitor = MONITORS.get(key);
            if (monitor != null) {
                return monitor;
            }
            monitor = createMonitor(url);
            if (monitor == null) {
                throw new IllegalStateException("Can not create monitor " + url);
            }
            MONITORS.put(key, monitor);
            return monitor;
        } finally {
            // 释放锁
            LOCK.unlock();
        }
    }