之前dubbo每隔十分钟左右会出现以下超时情况

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, server elapsed: 5022 ms, timeout: 5000 ms, request: Request [id=438870, version=2.0.0, twoway=true, event=false, broken=false, data=RpcInvocation [methodName=querySeatByCode, parameterTypes=[class java.lang.String, class java.lang.String], arguments=[99925788, A1], attachments={input=356, path=com.dfire.soa.turtle.service.ISeatService, interface=com.dfire.soa.turtle.service.ISeatService, timeout=5000, version=1.0.0H5_pressuretest}]], channel: /10.1.5.128:34443 -> /10.1.5.172:20880

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();
        }
    }