Hadoop集群环境搭建中一个错误的解决方案

本文转自我的ChinaUnix博客： http://blog.chinaunix.net/u3/107162/showart_2204785.html

2010-03-29 

环境已经搭好并可以启动了，如下：

1. maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ bin/start-all.sh
   
2. starting namenode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-namenode-maohong-desktop.out
   
3. slave1: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-debian.out
   
4. slave2: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-node2.out
   
5. master: starting datanode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-datanode-maohong-desktop.out
   
6. master: starting secondarynamenode, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-secondarynamenode-maohong-desktop.out
   
7. starting jobtracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-jobtracker-maohong-desktop.out
   
8. slave1: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-debian.out
   
9. slave2: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-node2.out
   
10. master: starting tasktracker, logging to /home/maohong/Software/Development/Hadoop/hadoop-0.20.2/bin/../logs/hadoop-maohong-tasktracker-maohong-desktop.out
    
11. maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ jps
    
12. 22565 SecondaryNameNode
    
13. 22646 JobTracker
    
14. 22342 DataNode
    
15. 22907 Jps
    
16. 22115 NameNode
    
17. 22861 TaskTracker

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

1. maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$ bin/hadoop jar hadoop-0.20.2-examples.jar wordcount test-in test-out
   
2. 10/03/25 19:40:05 INFO input.FileInputFormat: Total input paths to process : 4
   
3. 10/03/25 19:40:05 INFO mapred.JobClient: Running job: job_201003251936_0001
   
4. 10/03/25 19:40:06 INFO mapred.JobClient:  map 0% reduce 0%
   
5. 10/03/25 19:40:13 INFO mapred.JobClient:  map 50% reduce 0%
   
6. 10/03/25 19:40:14 INFO mapred.JobClient:  map 100% reduce 0%
   
7. 10/03/25 19:40:21 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_0, Status : FAILED
   
8. Error: java.lang.NullPointerException
   
9.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
   
10.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
11.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
12. 
    
13. 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
    
14. 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
    
15. 10/03/25 19:40:27 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_1, Status : FAILED
    
16. Error: java.lang.NullPointerException
    
17.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
18.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
19.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
20. 
    
21. 10/03/25 19:40:27 WARN mapred.JobClient: Error reading task outputnode2.1036dhcp
    
22. 10/03/25 19:40:27 WARN mapred.JobClient: Error reading task outputnode2.1036dhcp
    
23. 10/03/25 19:40:36 INFO mapred.JobClient: Task Id : attempt_201003251936_0001_r_000000_2, Status : FAILED
    
24. Error: java.lang.NullPointerException
    
25.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
26.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
27.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
28. 
    
29. 10/03/25 19:40:45 INFO mapred.JobClient: Job complete: job_201003251936_0001
    
30. 10/03/25 19:40:45 INFO mapred.JobClient: Counters: 12
    
31. 10/03/25 19:40:45 INFO mapred.JobClient:   Job Counters
    
32. 10/03/25 19:40:45 INFO mapred.JobClient:     Launched reduce tasks=4
    
33. 10/03/25 19:40:45 INFO mapred.JobClient:     Launched map tasks=4
    
34. 10/03/25 19:40:45 INFO mapred.JobClient:     Data-local map tasks=4
    
35. 10/03/25 19:40:45 INFO mapred.JobClient:     Failed reduce tasks=1
    
36. 10/03/25 19:40:45 INFO mapred.JobClient:   FileSystemCounters
    
37. 10/03/25 19:40:45 INFO mapred.JobClient:     HDFS_BYTES_READ=8637
    
38. 10/03/25 19:40:45 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=11495
    
39. 10/03/25 19:40:45 INFO mapred.JobClient:   Map-Reduce Framework
    
40. 10/03/25 19:40:45 INFO mapred.JobClient:     Combine output records=900
    
41. 10/03/25 19:40:45 INFO mapred.JobClient:     Map input records=83
    
42. 10/03/25 19:40:45 INFO mapred.JobClient:     Spilled Records=900
    
43. 10/03/25 19:40:45 INFO mapred.JobClient:     Map output bytes=14697
    
44. 10/03/25 19:40:45 INFO mapred.JobClient:     Combine input records=1525
    
45. 10/03/25 19:40:45 INFO mapred.JobClient:     Map output records=1525
    
46. maohong@maohong-desktop:~/Software/Development/Hadoop/hadoop-0.20.2$

jobtracker的log文件如下：

1. 2010-03-25 19:40:09,447 INFO org.apache.hadoop.mapred.JobInProgress: Choosing data-local task task_201003251936_0001_m_000003
   
2. 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.
   
3. 2010-03-25 19:40:12,268 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:1  completedMapsInputSize:4275  completedMapsOutputSize:5190
   
4. 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.
   
5. 2010-03-25 19:40:12,271 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:2  completedMapsInputSize:5745  completedMapsOutputSize:7302
   
6. 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'
   
7. 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.
   
8. 2010-03-25 19:40:12,522 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:3  completedMapsInputSize:7215  completedMapsOutputSize:9414
   
9. 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.
   
10. 2010-03-25 19:40:12,524 INFO org.apache.hadoop.mapred.ResourceEstimator: completedMapsUpdates:4  completedMapsInputSize:8641  completedMapsOutputSize:11367
    
11. 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
    
12.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
13.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
14.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
15. 
    
16. 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'
    
17. 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'
    
18. 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'
    
19. 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
    
20.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
21.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
22.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
23. 
    
24. 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'
    
25. 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'
    
26. 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'
    
27. 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
    
28.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
29.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
30.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
31. 
    
32. 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'
    
33. 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'
    
34. 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'
    
35. 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
    
36.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
    
37.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
    
38.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
    
39. 
    
40. 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'
    
41. 2010-03-25 19:40:42,278 INFO org.apache.hadoop.mapred.TaskInProgress: TaskInProgress task_201003251936_0001_r_000000 has failed 4 times.
    
42. 2010-03-25 19:40:42,278 INFO org.apache.hadoop.mapred.JobInProgress: Aborting job job_201003251936_0001
    
43. 2010-03-25 19:40:42,279 INFO org.apache.hadoop.mapred.JobInProgress: Killing job 'job_201003251936_0001'
    
44. 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'
    
45. 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'
    
46. 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.
    
47. 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'
    
48. 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'
    
49. 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'
    
50. 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'
    
51. 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'
    
52. 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'
    
53. 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'
    
54. 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'
    
55. 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'
    
56. 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：

1. 2010-03-25 19:40:30,249 INFO org.apache.hadoop.mapred.TaskTracker: Trying to launch : attempt_201003251936_0001_r_000000_2
   
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
   
3. 2010-03-25 19:40:30,587 INFO org.apache.hadoop.mapred.JvmManager: In JvmRunner constructed JVM ID: jvm_201003251936_0001_r_1711860611
   
4. 2010-03-25 19:40:30,588 INFO org.apache.hadoop.mapred.JvmManager: JVM Runner jvm_201003251936_0001_r_1711860611 spawned.
   
5. 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
   
6. 2010-03-25 19:40:31,437 FATAL org.apache.hadoop.mapred.TaskTracker: Task: attempt_201003251936_0001_r_000000_2 - Killed : java.lang.NullPointerException
   
7.         at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
   
8.         at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
   
9.         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