我正在与 hadoop teragen 一起使用 terasort 检查 hadoop mapreduce 基准测试。但是当我运行以下命令时，
hadoop jar /Users/**/Documents/hadoop-2.6.4/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.6.4.jar teragen -Dmapreduce.job.maps=100 1t 随机数据
我得到了以下异常，
17/06/01 15:09:21 WARN util.NativeCodeLoader: Unable to load native-hadoop
library for your platform... using builtin-java classes where applicable
17/06/01 15:09:22 INFO client.RMProxy: Connecting to ResourceManager at /127.0.0.1:8032
17/06/01 15:09:23 INFO terasort.TeraSort: Generating -727379968 using 100
17/06/01 15:09:23 INFO mapreduce.JobSubmitter: number of splits:100
17/06/01 15:09:23 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1496303775726_0003
17/06/01 15:09:23 INFO impl.YarnClientImpl: Submitted application application_1496303775726_0003
17/06/01 15:09:23 INFO mapreduce.Job: The url to track the job: http://localhost:8088/proxy/application_1496303775726_0003/
17/06/01 15:09:23 INFO mapreduce.Job: Running job: job_1496303775726_0003
17/06/01 15:09:27 INFO mapreduce.Job: Job job_1496303775726_0003 running in uber mode : false
17/06/01 15:09:27 INFO mapreduce.Job: map 0% reduce 0%
17/06/01 15:09:27 INFO mapreduce.Job: Job job_1496303775726_0003 failed with state FAILED due to: Application application_1496303775726_0003 failed 2 times due to AM Container for appattempt_1496303775726_0003_000002 exited with exitCode: -1000
For more detailed output, check application tracking page:http://localhost:8088/proxy/application_1496303775726_0003/Then, click on links to logs of each attempt.
Diagnostics: Call From KV.local/172.20.12.168 to localhost:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
java.net.ConnectException: Call From KV.local/172.20.12.168 to localhost:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
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:791)
at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:731)
at org.apache.hadoop.ipc.Client.call(Client.java:1473)
at org.apache.hadoop.ipc.Client.call(Client.java:1400)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:232)
at com.sun.proxy.$Proxy34.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getFileInfo(ClientNamenodeProtocolTranslatorPB.java:752)
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.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy35.getFileInfo(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:1977)
at org.apache.hadoop.hdfs.DistributedFileSystem$18.doCall(DistributedFileSystem.java:1118)
at org.apache.hadoop.hdfs.DistributedFileSystem$18.doCall(DistributedFileSystem.java:1114)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1114)
at org.apache.hadoop.yarn.util.FSDownload.copy(FSDownload.java:251)
at org.apache.hadoop.yarn.util.FSDownload.access$000(FSDownload.java:61)
at org.apache.hadoop.yarn.util.FSDownload$2.run(FSDownload.java:359)
at org.apache.hadoop.yarn.util.FSDownload$2.run(FSDownload.java:357)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1656)
at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:356)
at org.apache.hadoop.yarn.util.FSDownload.call(FSDownload.java:60)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Connection refused
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:530)
at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:494)
at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:608)
at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:706)
at org.apache.hadoop.ipc.Client$Connection.access$2800(Client.java:369)
at org.apache.hadoop.ipc.Client.getConnection(Client.java:1522)
at org.apache.hadoop.ipc.Client.call(Client.java:1439)
... 31 more
如错误所示，它无法连接到 localhost:8020，但是当我检查 namenode Web UI 时，它显示 namenode 处于活动状态。请看下面的截图：
我发现了很多与此相关的帖子，但没有一个能帮助我。我还检查了 hosts 文件，其中包含以下行：
127.0.0.1 本地主机
172.20.12.168 本地主机
谁能帮我解决这个问题？