今天配置hbase的时候发现有几台机器的regionserver启不来。报错如下：
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.apache.Hadoop.ipc.RemoteException.instantiateException(RemoteException.java:95)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:79)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:1506)
at org.apache.hadoop.hbase.regionserver.HRegionServer.tryReportForDuty(HRegionServer.java:1470)
at org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:563)
at java.lang.Thread.run(Thread.java:662)
Caused by: org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.hbase.ClockOutOfSyncException: Server s3,60020,1304927875246 has been rejected; Reported time is too far out of sync with master. Time difference of 41450ms > max allowed of 30000ms
at org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:181)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:129)
at org.apache.hadoop.hbase.master.HMaster.regionServerStartup(HMaster.java:613)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:570)
at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1039)
at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:771)
at org.apache.hadoop.hbase.ipc.HBaseRPC$Invoker.invoke(HBaseRPC.java:257)
at $Proxy5.regionServerStartup(Unknown Source)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:1502)
错误里指出节点机的时间和master的时间差距大于30000ms，就是30秒时无法启动服务。之前hadoop没有遇到过这个问题，所以hbase存在系统时间同步的问题，并且误差要再30s以内。
在网上查了一下，要配置服务器时间同步需要用到ntp，最好能连接外网的时间服务器。内网里面配起来比较麻烦点，所以就手动改了时间，再启动就可以了。
还有另外一个方案，就是修改hbase最大时间误差。
在hbase-site.xml添加配置 hbase.master.maxclockskew 180000 Time difference of regionserver from master