Java 获取本地主机 UnknownHostException

问题描述

启动 DubboX 应用时报错：

[WARN ]-[2016-08-02 10:47:15]-[com.alibaba.dubbo.config.AbstractConfig:305]:[DUBBO] my_host_name: my_host_name: unknown error, dubbo version: 2.8.4, current host: 127.0.0.1
java.net.UnknownHostException: my_host_name: my_host_name: unknown error
        at java.net.InetAddress.getLocalHost(InetAddress.java:1505)
        at com.alibaba.dubbo.config.ServiceConfig.doExportUrlsFor1Protocol(ServiceConfig.java:303)
        at com.alibaba.dubbo.config.ServiceConfig.doExportUrls(ServiceConfig.java:285)
        at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:246)
        at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:145)
        at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:110)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:96)
        at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:334)
        at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:948)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482)
        at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
        at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)
        at com.alibaba.dubbo.container.spring.SpringContainer.start(SpringContainer.java:50)
        at com.alibaba.dubbo.container.Main.main(Main.java:80)
        at net.xxx.xxx.Server.main(Server.java:33)
Caused by: java.net.UnknownHostException: my_host_name: unknown error
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928)
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323)
        at java.net.InetAddress.getLocalHost(InetAddress.java:1500)
        ... 14 more
​

排查解决

在这台服务器上执行 hostname 命令，正常返回了主机名，然后 ping 这个主机名报错：ping: unknown host my_host_name，使用 hostname -i（通过主机名解析 IP 地址）时也会报错：

• CentOS：hostname: Unknown host
• Ubuntu：hostname: Name or service not known

该问题是由于通过主机名解析不到 IP 引起的，前段时间曾经修改过主机名，但是没改全：除了执行 hostname my_host_name 外还需要执行：

• CentOS：需要修改 /etc/sysconfig/network 中的 HOSTNAME 配置项
• Ubuntu：需要修改 /etc/hostname

改完后重启就好了 😄 ，如果不方便重启，也可以把新的主机名先加在 /etc/hosts 里面，通过“本地 DNS”进行解析吧。