Hadoop集群环境搭建中一个错误的解决方案

posir

　　本文转自我的ChinaUnix博客： http://blog.iyunv.com/u3/107162/showart_2204785.html
　　2010-03-29 


环境已经搭好并可以启动了，如下：

• maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ bin/start-all.sh
  
• starting namenode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-namenode-maohong-desktop.out
  
• slave1: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-debian.out
  
• slave2: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-node2.out
  
• master: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-maohong-desktop.out
  
• master: starting secondarynamenode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-secondarynamenode-maohong-desktop.out
  
• starting jobtracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-jobtracker-maohong-desktop.out
  
• slave1: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-debian.out
  
• slave2: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-node2.out
  
• master: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-maohong-desktop.out
  
• maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ jps
  
• 22565 SecondaryNameNode
  
• 22646 JobTracker
  
• 22342 DataNode
  
• 22907 Jps
  
• 22115 NameNode
  
• 22861 TaskTracker
  

但是执行wordcount程序到时候出现Error: java.lang.NullPointerException错误如下：

• maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ bin/hadoop jar hadoop-0.20.2-examples.jar wordcount test-in test-out
  
• 10/03/25 19:40:05 INFO input.FileInputFormat: Total input paths to process : 4
  
• 10/03/25 19:40:05 INFO mapred.JobClient: Running job: job_201003251936_0001
  
• 10/03/25 19:40:06 INFO mapred.JobClient:  map 0% reduce 0%
  
• 10/03/25 19:40:13 INFO mapred.JobClient:  map 50% reduce 0%
  
• 10/03/25 19:40:14 INFO mapred.JobClient:  map 100% reduce 0%
  
• 10/03/25 19:40:21 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_0, Status : FAILED
  
• Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 10/03/25 19:40:21 WARN mapred.JobClient: Error reading task outputhttp://localhost:50060/tasklog?plaintext=true&taskid=attempt_201003251936_0001_r_000000_0&filter=stdout
  
• 10/03/25 19:40:21 WARN mapred.JobClient: Error reading task outputhttp://localhost:50060/tasklog?plaintext=true&taskid=attempt_201003251936_0001_r_000000_0&filter=stderr
  
• 10/03/25 19:40:27 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_1, Status : FAILED
  
• Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 10/03/25 19:40:27 WARN mapred.JobClient: Error reading task outputnode2.1036dhcp
  
• 10/03/25 19:40:27 WARN mapred.JobClient: Error reading task outputnode2.1036dhcp
  
• 10/03/25 19:40:36 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_2, Status : FAILED
  
• Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 10/03/25 19:40:45 INFO mapred.JobClient: Job complete: job_201003251936_0001
  
• 10/03/25 19:40:45 INFO mapred.JobClient: Counters: 12
  
• 10/03/25 19:40:45 INFO mapred.JobClient:   Job Counters
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Launched reduce tasks=4
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Launched map tasks=4
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Data-local map tasks=4
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Failed reduce tasks=1
  
• 10/03/25 19:40:45 INFO mapred.JobClient:   FileSystemCounters
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     HDFS_BYTES_READ=8637
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=11495
  
• 10/03/25 19:40:45 INFO mapred.JobClient:   Map-Reduce Framework
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Combine output records=900
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Map input records=83
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Spilled Records=900
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Map output bytes=14697
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Combine input records=1525
  
• 10/03/25 19:40:45 INFO mapred.JobClient:     Map output records=1525
  
• maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$
  

jobtracker的log文件如下：

• 2010-03-25 19:40:09,447 INFO org.apache.hadoop.mapred.JobInProgress: Choosing data-local task task_201003251936_0001_m_000003
  
• 2010-03-25 19:40:12,268 INFO org.apache.hadoop.mapred.JobInProgress: Task 'attempt_201003251936_0001_m_000000_0' has completed task_201003251936_0001_m_000000 successfully.
  
• 2010-03-25 19:40:12,268 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:1  completedMapsInputSize:4275  completedMapsOutputSize:5190
  
• 2010-03-25 19:40:12,271 INFO org.apache.hadoop.mapred.JobInProgress: Task 'attempt_201003251936_0001_m_000001_0' has completed task_201003251936_0001_m_000001 successfully.
  
• 2010-03-25 19:40:12,271 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:2  completedMapsInputSize:5745  completedMapsOutputSize:7302
  
• 2010-03-25 19:40:12,288 INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201003251936_0001_r_000000_0' to tip task_201003251936_0001_r_000000, for tracker 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:12,522 INFO org.apache.hadoop.mapred.JobInProgress: Task 'attempt_201003251936_0001_m_000002_0' has completed task_201003251936_0001_m_000002 successfully.
  
• 2010-03-25 19:40:12,522 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:3  completedMapsInputSize:7215  completedMapsOutputSize:9414
  
• 2010-03-25 19:40:12,524 INFO org.apache.hadoop.mapred.JobInProgress: Task 'attempt_201003251936_0001_m_000003_0' has completed task_201003251936_0001_m_000003 successfully.
  
• 2010-03-25 19:40:12,524 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:4  completedMapsInputSize:8641  completedMapsOutputSize:11367
  
• 2010-03-25 19:40:18,300 INFO org.apache.hadoop.mapred.TaskInProgress: Error from attempt_201003251936_0001_r_000000_0: Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 2010-03-25 19:40:18,301 INFO org.apache.hadoop.mapred.JobTracker: Adding task (cleanup)'attempt_201003251936_0001_r_000000_0' to tip task_201003251936_0001_r_000000, for tracker 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:21,307 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_0' from 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:21,559 INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201003251936_0001_r_000000_1' to tip task_201003251936_0001_r_000000, for tracker 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  
• 2010-03-25 19:40:24,599 INFO org.apache.hadoop.mapred.TaskInProgress: Error from attempt_201003251936_0001_r_000000_1: Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 2010-03-25 19:40:24,600 INFO org.apache.hadoop.mapred.JobTracker: Adding task (cleanup)'attempt_201003251936_0001_r_000000_1' to tip task_201003251936_0001_r_000000, for tracker 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  
• 2010-03-25 19:40:27,607 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_1' from 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  
• 2010-03-25 19:40:30,201 INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201003251936_0001_r_000000_2' to tip task_201003251936_0001_r_000000, for tracker 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:33,260 INFO org.apache.hadoop.mapred.TaskInProgress: Error from attempt_201003251936_0001_r_000000_2: Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 2010-03-25 19:40:33,261 INFO org.apache.hadoop.mapred.JobTracker: Adding task (cleanup)'attempt_201003251936_0001_r_000000_2' to tip task_201003251936_0001_r_000000, for tracker 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:36,266 INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201003251936_0001_r_000000_3' to tip task_201003251936_0001_r_000000, for tracker 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:36,266 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_2' from 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:39,270 INFO org.apache.hadoop.mapred.TaskInProgress: Error from attempt_201003251936_0001_r_000000_3: Error: java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  
• 
  
• 2010-03-25 19:40:39,271 INFO org.apache.hadoop.mapred.JobTracker: Adding task (cleanup)'attempt_201003251936_0001_r_000000_3' to tip task_201003251936_0001_r_000000, for tracker 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:42,278 INFO org.apache.hadoop.mapred.TaskInProgress: TaskInProgress task_201003251936_0001_r_000000 has failed 4 times.
  
• 2010-03-25 19:40:42,278 INFO org.apache.hadoop.mapred.JobInProgress: Aborting job job_201003251936_0001
  
• 2010-03-25 19:40:42,279 INFO org.apache.hadoop.mapred.JobInProgress: Killing job 'job_201003251936_0001'
  
• 2010-03-25 19:40:42,279 INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201003251936_0001_m_000004_0' to tip task_201003251936_0001_m_000004, for tracker 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:42,279 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_3' from 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:45,288 INFO org.apache.hadoop.mapred.JobInProgress: Task 'attempt_201003251936_0001_m_000004_0' has completed task_201003251936_0001_m_000004 successfully.
  
• 2010-03-25 19:40:45,333 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000004_0' from 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:45,333 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_2' from 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:45,334 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_3' from 'tracker_maohong-desktop:localhost/127.0.0.1:60931'
  
• 2010-03-25 19:40:45,334 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000000_0' from 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:45,334 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000001_0' from 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:45,334 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000005_0' from 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:45,335 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_0' from 'tracker_localhost:localhost/127.0.0.1:38831'
  
• 2010-03-25 19:40:45,694 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000002_0' from 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  
• 2010-03-25 19:40:45,694 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_m_000003_0' from 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  
• 2010-03-25 19:40:45,694 INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201003251936_0001_r_000000_1' from 'tracker_node2.1036dhcp:localhost/127.0.0.1:59187'
  

其中一个tasktracker的log如下，另外两个tasktracker的log也有与此同样的错误：

• 2010-03-25 19:40:30,249 INFO org.apache.hadoop.mapred.TaskTracker: Trying to launch : attempt_201003251936_0001_r_000000_2
  
• 2010-03-25 19:40:30,249 INFO org.apache.hadoop.mapred.TaskTracker: In TaskLauncher, current free slots : 2 and trying to launch attempt_201003251936_0001_r_000000_2
  
• 2010-03-25 19:40:30,587 INFO org.apache.hadoop.mapred.JvmManager: In JvmRunner constructed JVM ID: jvm_201003251936_0001_r_1711860611
  
• 2010-03-25 19:40:30,588 INFO org.apache.hadoop.mapred.JvmManager: JVM Runner jvm_201003251936_0001_r_1711860611 spawned.
  
• 2010-03-25 19:40:31,057 INFO org.apache.hadoop.mapred.TaskTracker: JVM with ID: jvm_201003251936_0001_r_1711860611 given task: attempt_201003251936_0001_r_000000_2
  
• 2010-03-25 19:40:31,437 FATAL org.apache.hadoop.mapred.TaskTracker: Task: attempt_201003251936_0001_r_000000_2 - Killed : java.lang.NullPointerException
  
•         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
  
•         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
  

问题的原因在于master和slave节点的/etc/hosts文件~~~~~~
/etc/hosts文件中的主机名一定要是机器名，而不是master、slave1、slave2，否则不能正确解析。这就是结症所在！
 
改了之后就解决了，呵呵