14/04/29 02:45:07 INFO mapreduce.Job: Job job_1398704073313_0021 failed with state FAILED due to: Application application_1398704073313_0021 failed 2 times due to Error launching appattempt_1398704073313_0021_000002. Got exception: org.apache.hadoop.yarn.exceptions.YarnException: Unauthorized request to start container. ' F4 }0 C* `/ y# L9 A
This token is expired. current time is 1398762692768 found 1398711306590
        at sun.reflect.GeneratedConstructorAccessor30.newInstance(Unknown Source)5 [& j' H( j0 j9 _4 ?7 o; q6 m
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)7 g- {( w6 [( N) s" `
        at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
        at org.apache.hadoop.yarn.api.records.impl.pb.SerializedExceptionPBImpl.instantiateException(SerializedExceptionPBImpl.java:152)& n/ J* ]3 |& a2 q) t* g
        at org.apache.hadoop.yarn.api.records.impl.pb.SerializedExceptionPBImpl.deSerialize(SerializedExceptionPBImpl.java:106), B4 u7 G  f, f  d6 H
        at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.launch(AMLauncher.java:122)0 o+ [. u$ O; S' S- ?3 t. y
        at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.run(AMLauncher.java:249)/ z+ v$ o( g) j* p. G
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:722)
. Failing the application.6 N  G( N1 f9 l& K) z
14/04/29 02:45:07 INFO mapreduce.Job: Counters: 0

问题原因：namenode,datanode时间同步问题8 yc& L  f2 W. h/ q( v& K  
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解决办法：多个datanode与namenode进行时间同步，在每台服务器执行：ntpdate time.nist.gov，确认时间同步成功。6 q’ N6 }4 N8 u
最好在每台服务器的 /etc/crontab 中加入一行：
0 2 * * * root ntpdate time.nist.gov && hwclock –w