JAVA高级面试进阶训练营视频教程

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运行hadoop2 自带的圆周率计算方法时，报错，找了半天，原来是在配置hadoop临时目录时，没有给权限，找到配置的hadoop临时目录文件夹，修改权限即可

Application application_1548242073562_0005 failed 2 times due to AM Container for appattempt_1548242073562_0005_000002 exited with exitCode: 1
Failing this attempt.Diagnostics: [2019-01-23 20:50:53.319]Exception from container-launch.
Container id: container_1548242073562_0005_02_000001
Exit code: 1
[2019-01-23 20:50:53.321]Container exited with a non-zero exit code 1. Error file: prelaunch.err.
Last 4096 bytes of prelaunch.err :
Last 4096 bytes of stderr :
log4j:WARN No appenders could be found for logger (org.apache.hadoop.mapreduce.v2.app.MRAppMaster).
log4j:WARN Please initialize the log4j system properly.

计算少的时，比如1 1，不报错，如果计算稍微大的数字，如10 10 就直接报下面的异常

19/01/24 10:20:32 INFO ipc.Client: Retrying connect to server: 0.0.0.0/0.0.0.0:10020. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
java.io.IOException: java.net.ConnectException: Your endpoint configuration is wrong; For more details see:  http://wiki.apache.org/hadoop/UnsetHostnameOrPort
	at org.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:344)
	at org.apache.hadoop.mapred.ClientServiceDelegate.getJobStatus(ClientServiceDelegate.java:429)
	at org.apache.hadoop.mapred.YARNRunner.getJobStatus(YARNRunner.java:804)
	at org.apache.hadoop.mapreduce.Job$1.run(Job.java:331)
	at org.apache.hadoop.mapreduce.Job$1.run(Job.java:328)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1893)
	at org.apache.hadoop.mapreduce.Job.updateStatus(Job.java:328)
	at org.apache.hadoop.mapreduce.Job.isSuccessful(Job.java:624)
	at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1603)
	at org.apache.hadoop.examples.QuasiMonteCarlo.estimatePi(QuasiMonteCarlo.java:307)
	at org.apache.hadoop.examples.QuasiMonteCarlo.run(QuasiMonteCarlo.java:360)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
	at org.apache.hadoop.examples.QuasiMonteCarlo.main(QuasiMonteCarlo.java:368)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:71)
	at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
	at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:74)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.util.RunJar.run(RunJar.java:244)
	at org.apache.hadoop.util.RunJar.main(RunJar.java:158)
Caused by: java.net.ConnectException: Your endpoint configuration is wrong; For more details see:  http://wiki.apache.org/hadoop/UnsetHostnameOrPort
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:824)
	at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:750)
	at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1511)
	at org.apache.hadoop.ipc.Client.call(Client.java:1453)
	at org.apache.hadoop.ipc.Client.call(Client.java:1363)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:227)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116)
	at com.sun.proxy.$Proxy15.getJobReport(Unknown Source)
	at org.apache.hadoop.mapreduce.v2.api.impl.pb.client.MRClientProtocolPBClientImpl.getJobReport(MRClientProtocolPBClientImpl.java:133)
	at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:325)
	... 27 more
Caused by: java.net.ConnectException: Connection refused
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
	at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
	at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
	at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:690)
	at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:794)
	at org.apache.hadoop.ipc.Client$Connection.access$3600(Client.java:412)
	at org.apache.hadoop.ipc.Client.getConnection(Client.java:1568)
	at org.apache.hadoop.ipc.Client.call(Client.java:1399)
	... 36 more

　　后来在这里找到了答案https://blog.csdn.net/zhouyan8603/article/details/47398245，，hadoop的datanode需要访问namenode的jobhistory server,如果没有修改，则默认为0.0.0.0:10020，则可以修改mapred-site.xml文件：

<property>
    <name>mapreduce.jobhistory.address</name>
       <!-- 配置实际的Master主机名和端口-->
    <value>0.0.0.0:10020</value>
</property>


<property>
    <name>mapreduce.jobhistory.webapp.address</name>
       <!-- 配置实际的Master主机名和端口-->
    <value>0.0.0.0:19888</value>
</property> 

然后启动historyserver，再尝试10 10  完成

$HADOOP_HOME/sbin/mr-jobhistory-daemon.sh start historyserver