運行python hadoop streaming 參數如下時：
hadoop jar $HADOOP_HOME/contrib/hadoop-streaming.jar
-mapper /usr/local/mapper.py //本地mapper.py文件地址
-reducer /usr/local/reducer.py //本地reducer.py文件地址
-input /user/root/test/word //hdfs文件地址
-output /user/root/test/output //hdfs 文件地址
會出現如下錯誤：
Error: java.lang.RuntimeException: Error in configuring object
at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:109)
at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:75)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:133)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:426)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:342)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:167)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1554)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:162)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:106)
... 9 more
Caused by: java.lang.RuntimeException: Error in configuring object
at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:109)
at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:75)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:133)
at org.apache.hadoop.mapred.MapRunner.configure(MapRunner.java:38)
... 14 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:106)
... 17 more
Caused by: java.lang.RuntimeException: configuration exception
at org.apache.hadoop.streaming.PipeMapRed.configure(PipeMapRed.java:222)
at org.apache.hadoop.streaming.PipeMapper.configure(PipeMapper.java:66)
... 22 more
Caused by: java.io.IOException: Cannot run program "/usr/local/mapper.py": error=2, No such file or directory
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1041)
at org.apache.hadoop.streaming.PipeMapRed.configure(PipeMapRed.java:209)
... 23 more
Caused by: java.io.IOException: error=2, No such file or directory
at java.lang.UNIXProcess.forkAndExec(Native Method)
at java.lang.UNIXProcess.<init>(UNIXProcess.java:186)
at java.lang.ProcessImpl.start(ProcessImpl.java:130)
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1022)
正確參數設置如下：
hadoop jar $HADOOP_HOME/contrib/hadoop-streaming.jar
-files /usr/local/mapper.py,/usr/local/reducer.py //此處也可以爲 -file /usr/local/mapper.py -file /usr/local/reducer.py
-mapper mapper.py //本地mapper.py文件地址
-reducer reducer.py //本地reducer.py文件地址
-input /user/root/test/word //hdfs文件地址
-output /user/root/test/output //hdfs 文件地址
如果想要設置map和reduce任務數據，在-input前添加-D mapred.map.tasks=num -D mapred.reduce.tasks=num
注意：-D操作設置在-input和之前。