请教初学mapreduce的一个问题

[汇讯猎头]

请教大家一个问题：本人初学hadoop，运行mapreduce的第一个最简单的实验，就是运行那个wordcount的任务，最后任务虽然完成了，但是有以下报错，请教一下论坛高人，这段报错是什么意思？我看不懂，该如何解决呢？多谢！

任务运行过程的最后几行提示信息、以及后来出现的报错信息如下：
16/05/17 17:28:05 INFO mapreduce.Job: map 100% reduce 100%
16/05/17 17:30:30 INFO mapreduce.Job: Jobjob_1463471812041_0001 completed successfully
16/05/17 17:30:52 INFO mapreduce.Job:Counters: 43
FileSystem Counters
FILE:Number of bytes read=86
FILE:Number of bytes written=157907
FILE:Number of read operations=0
FILE:Number of large read operations=0
FILE:Number of write operations=0
HDFS:Number of bytes read=174
HDFS:Number of bytes written=52
HDFS:Number of read operations=6
HDFS: Number of large read operations=0
HDFS:Number of write operations=2
JobCounters
Launchedmap tasks=1
Launchedreduce tasks=1
Data-localmap tasks=1
Totaltime spent by all maps in occupied slots (ms)=264323
Totaltime spent by all reduces in occupied slots (ms)=175714
Map-ReduceFramework
Mapinput records=7
Mapoutput records=14
Mapoutput bytes=134
Mapoutput materialized bytes=86
Inputsplit bytes=96
Combineinput records=14
Combineoutput records=7
Reduceinput groups=7
Reduceshuffle bytes=86
Reduceinput records=7
Reduceoutput records=7
SpilledRecords=14
ShuffledMaps =1
FailedShuffles=0
MergedMap outputs=1
GCtime elapsed (ms)=15961
CPUtime spent (ms)=5400
Physicalmemory (bytes) snapshot=156418048
Virtualmemory (bytes) snapshot=4127854592
Totalcommitted heap usage (bytes)=130084864
ShuffleErrors
BAD_ID=0
CONNECTION=0
IO_ERROR=0
WRONG_LENGTH=0
WRONG_MAP=0
WRONG_REDUCE=0
FileInput Format Counters
BytesRead=78
FileOutput Format Counters
BytesWritten=52
16/05/17 17:30:55 INFO ipc.Client: Retryingconnect to server: host12/10.0.2.12:45306. Already tried 0 time(s); retrypolicy is RetryUpToMaximumCountWithFixedSleep(maxRetries=3, sleepTime=1 SECONDS)
16/05/17 17:30:56 INFO ipc.Client: Retryingconnect to server: host12/10.0.2.12:45306. Already tried 1 time(s); retrypolicy is RetryUpToMaximumCountWithFixedSleep(maxRetries=3, sleepTime=1SECONDS)
16/05/17 17:30:57 INFO ipc.Client: Retryingconnect to server: host12/10.0.2.12:45306. Already tried 2 time(s); retrypolicy is RetryUpToMaximumCountWithFixedSleep(maxRetries=3, sleepTime=1SECONDS)
16/05/17 17:30:58 INFOmapred.ClientServiceDelegate: Application state is completed.FinalApplicationStatus=SUCCEEDED. Redirecting to job history server
16/05/17 17:30:59 INFO ipc.Client: Retryingconnect to server: 0.0.0.0/0.0.0.0:10020. Already tried 0 time(s); retry policyis RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)
……发帖字数限制 中间省略一部分

16/05/17 17:31:29 ERRORsecurity.UserGroupInformation: PriviledgedActionException as:root (auth:SIMPLE)cause:java.io.IOException: java.net.ConnectException: Call From host12/10.0.2.12to 0.0.0.0:10020 failed on connection exception: java.net.ConnectException: 拒绝连接; Formore details see: http://wiki.apache.org/hadoop/ConnectionRefused
java.io.IOException:java.net.ConnectException: Call From host12/10.0.2.12 to 0.0.0.0:10020 failedon connection exception: java.net.ConnectException: 拒绝连接; Formore details see: http://wiki.apache.org/hadoop/ConnectionRefused
atorg.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:331)
atorg.apache.hadoop.mapred.ClientServiceDelegate.getJobStatus(ClientServiceDelegate.java:416)
atorg.apache.hadoop.mapred.YARNRunner.getJobStatus(YARNRunner.java:522)
atorg.apache.hadoop.mapreduce.Job$1.run(Job.java:314)
atorg.apache.hadoop.mapreduce.Job$1.run(Job.java:311)
atjava.security.AccessController.doPrivileged(Native Method)
atjavax.security.auth.Subject.doAs(Subject.java:422)
atorg.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491)
atorg.apache.hadoop.mapreduce.Job.updateStatus(Job.java:311)
atorg.apache.hadoop.mapreduce.Job.isSuccessful(Job.java:611)
atorg.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1301)
atorg.apache.hadoop.examples.WordCount.main(WordCount.java:84)
atsun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:498)
atorg.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:72)
atorg.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
atorg.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:74)
atsun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:498)
atorg.apache.hadoop.util.RunJar.main(RunJar.java:212)
Caused by: java.net.ConnectException: CallFrom host12/10.0.2.12 to 0.0.0.0:10020 failed on connection exception:java.net.ConnectException: 拒绝连接; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
atsun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
atsun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
atsun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
atjava.lang.reflect.Constructor.newInstance(Constructor.java:423)
atorg.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:783)
atorg.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:730)
atorg.apache.hadoop.ipc.Client.call(Client.java:1351)
atorg.apache.hadoop.ipc.Client.call(Client.java:1300)
atorg.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206)
atcom.sun.proxy.$Proxy10.getJobReport(Unknown Source)
atorg.apache.hadoop.mapreduce.v2.api.impl.pb.client.MRClientProtocolPBClientImpl.getJobReport(MRClientProtocolPBClientImpl.java:133)
atsun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:498)
atorg.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:317)
...23 more
Caused by: java.net.ConnectException: 拒绝连接
atsun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
atsun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
atorg.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
atorg.apache.hadoop.net.NetUtils.connect(NetUtils.java:529)
atorg.apache.hadoop.net.NetUtils.connect(NetUtils.java:493)
atorg.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:547)
atorg.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:642)
atorg.apache.hadoop.ipc.Client$Connection.access$2600(Client.java:314)
atorg.apache.hadoop.ipc.Client.getConnection(Client.java:1399)
atorg.apache.hadoop.ipc.Client.call(Client.java:1318)
...31 more
[root@host12 mapreduce]#
烦请高人指点，以上报错是什么意思？该如何解决？谢谢！

[wocawuliao]

拒绝链接是不是防火墙没有配置好！！！

[Q-WHai]

楼上 +1

[镜中夜]

以本地模式运行hadoop时，抛异常 ERROR security.UserGroupInformation: PriviledgedActionException as:hadoop cause:java.net.UnknownHostException: hadoop: hadoop: Name or service not known Exception in thread "main" java.net.UnknownHostException: hadoop: hadoop: Name or service not known 把/etc/hostname文件中的主机名加入到/etc/hosts文件中，问题解决。