Jobtracker HA启动时备机jobtracker无法启动，报rpc version mismatch

昨天在重启jobtracker HA的时候碰到怪异问题，备机的jobtracker无法启动

备机上的错误日志

13/10/29 16:45:53 ERROR mapred.JobTrackerHADaemon: java.net.BindException: Problem binding to [mynamenode01:48023] java.net.BindException: Cannot assign requested address; For more details see:  http://wiki.apache.org/hadoop/BindException
        at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:715)
        at org.apache.hadoop.ipc.Server.bind(Server.java:356)
        at org.apache.hadoop.ipc.Server$Listener.(Server.java:454)
        at org.apache.hadoop.ipc.Server.(Server.java:1835)
        at org.apache.hadoop.ipc.RPC$Server.(RPC.java:970)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server.(ProtobufRpcEngine.java:375)
        at org.apache.hadoop.ipc.ProtobufRpcEngine.getServer(ProtobufRpcEngine.java:350)
        at org.apache.hadoop.ipc.RPC.getServer(RPC.java:695)
        at org.apache.hadoop.ipc.RPC.getServer(RPC.java:659)
        at org.apache.hadoop.mapred.JobTrackerHADaemon.start(JobTrackerHADaemon.java:107)
        at org.apache.hadoop.mapred.JobTrackerHADaemon.startService(JobTrackerHADaemon.java:160)
        at org.apache.hadoop.mapred.JobTrackerHADaemon.main(JobTrackerHADaemon.java:166)

按照http://wiki.apache.org/hadoop/BindException上的提示

从mynamenode02 telnet 到mynamenode01的48023端口，之后提示

)org.apache.hadoop.ipc.RPC$VersionMismatch>Server IPC version 7 cannot communicate with client version 13Connection closed by foreign host.

后来同事发现是MRv1的mapred-site.xml文件被错误修改；果然就像以前看的hadoop trouble shooting上说的，80%的hadoop错误都来自于错误的配置。