有一段时间没有启动过Hbase,重新启动HBase数据库时候，发现有一个节点没有启动，查看其启动日志，可以看到它抛出了ClockOutOfSyncException异常，具体的异常如下所示：
2017-04-23 20:18:28,975 FATAL [regionserver/node2/192.168.8.119:16020] regionserver.HRegionServer: Master rejected startup because clock is out of sync
org.apache.hadoop.hbase.ClockOutOfSyncException: org.apache.hadoop.hbase.ClockOutOfSyncException: Server node2,16020,1492949885855 has been rejected; Reported time is too far out of sync with master. Time difference of 71531ms > max allowed of 30000msat org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:388)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:262)
at org.apache.hadoop.hbase.master.MasterRpcServices.regionServerStartup(MasterRpcServices.java:322)
atorg.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$2.callBlockingMethod(RegionServerStatusProtos.java:8615)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2117)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:104)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:133)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:108)
at java.lang.Thread.run(Thread.java:745)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:95)
at org.apache.hadoop.hbase.protobuf.ProtobufUtil.getRemoteException(ProtobufUtil.java:325)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:2271)
at org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:893)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.hadoop.hbase.ipc.RemoteWithExtrasException(org.apache.hadoop.hbase.ClockOutOfSyncException): org.apache.hadoop.hbase.ClockOutOfSyncException: Server node2,16020,1492949885855 has been rejected; Reported time is too far out of sync with master. Time difference of 71531ms > max allowed of 30000ms
at org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:388)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:262)
at org.apache.hadoop.hbase.master.MasterRpcServices.regionServerStartup(MasterRpcServices.java:322)
at org.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$2.callBlockingMethod(RegionServerStatusProtos.java:8615)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2117)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:104)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:133)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:108)
at java.lang.Thread.run(Thread.java:745)
at org.apache.hadoop.hbase.ipc.RpcClientImpl.call(RpcClientImpl.java:1235)
at org.apache.hadoop.hbase.ipc.AbstractRpcClient.callBlockingMethod(AbstractRpcClient.java:217)
at org.apache.hadoop.hbase.ipc.AbstractRpcClient$BlockingRpcChannelImplementation.callBlockingMethod(AbstractRpcClient.java:318)
atorg.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$BlockingStub.regionServerStartup(RegionServerStatusProtos.java:8982)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:2269)... 2 more
2017-04-23 20:18:28,979 FATAL [regionserver/node2/192.168.8.119:16020] regionserver.HRegionServer: ABORTING region server node2,16020,1492949885855: Unhandled: org.apache.hadoop.hbase.ClockOutOfSyncException: Server node2,16020,1492949885855 has been rejected; Reported time is too far out of sync with master. Time difference of 71531ms > max allowed of 30000ms
at org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:388)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:262)
at org.apache.hadoop.hbase.master.MasterRpcServices.regionServerStartup(MasterRpcServices.java:322)
atorg.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$2.callBlockingMethod(RegionServerStatusProtos.java:8615)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2117)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:104)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:133)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:108)
at java.lang.Thread.run(Thread.java:745)
org.apache.hadoop.hbase.ClockOutOfSyncException: org.apache.hadoop.hbase.ClockOutOfSyncException: Server node2,16020,1492949885855 has been rejected; Reported time is too far out of sync with master. Time difference of 71531ms > max allowed of 30000ms
at org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:388)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:262)
at org.apache.hadoop.hbase.master.MasterRpcServices.regionServerStartup(MasterRpcServices.java:322)
atorg.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$2.callBlockingMethod(RegionServerStatusProtos.java:8615)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2117)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:104)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:133)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:108)
at java.lang.Thread.run(Thread.java:745)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:95)
at org.apache.hadoop.hbase.protobuf.ProtobufUtil.getRemoteException(ProtobufUtil.java:325)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:2271)
at org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:893)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.hadoop.hbase.ipc.RemoteWithExtrasException(org.apache.hadoop.hbase.ClockOutOfSyncException): org.apache.hadoop.hbase.ClockOutOfSyncException: Server node2,16020,1492949885855 has been rejected; Reported time is too far out of sync with master. Time difference of 71531ms > max allowed of 30000ms
at org.apache.hadoop.hbase.master.ServerManager.checkClockSkew(ServerManager.java:388)
at org.apache.hadoop.hbase.master.ServerManager.regionServerStartup(ServerManager.java:262)
at org.apache.hadoop.hbase.master.MasterRpcServices.regionServerStartup(MasterRpcServices.java:322)
at org.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$2.callBlockingMethod(RegionServerStatusProtos.java:8615)
at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2117)
at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:104)
at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:133)
at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:108)
at java.lang.Thread.run(Thread.java:745)
at org.apache.hadoop.hbase.ipc.RpcClientImpl.call(RpcClientImpl.java:1235)
at org.apache.hadoop.hbase.ipc.AbstractRpcClient.callBlockingMethod(AbstractRpcClient.java:217)
atorg.apache.hadoop.hbase.ipc.AbstractRpcClient$BlockingRpcChannelImplementation.callBlockingMethod(AbstractRpcClient.java:318)
atorg.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos$RegionServerStatusService$BlockingStub.regionServerStartup(RegionServerStatusProtos.java:8982)
at org.apache.hadoop.hbase.regionserver.HRegionServer.reportForDuty(HRegionServer.java:2269 )
通过日志分析，可以发现Master节点和node2节点之间的连接用时71531ms，超过了默认的时间30000ms，具体为什么会
连接超时，可能是硬件原因，也可能是软件问题。现在解决办法就是在Master节点配置连接时间的属性，时间设置大一些
在Master节点的HBase配置文件hbase-siter.xml中添加连接时长的属性，然后重新启动Hbase就行了。
<property>
<name>hbase.master.maxclockskew</name>
<value>120000</value>
</property>