hadoop上的python流式mapreduce作业失败-缺少log4j？

Question

我尝试在安装在 Ubuntu 15.10 上的 hadoop 2.7.1 上运行 python wordcount，但出现错误：

log4j:WARN No appenders could be found for logger (org.apache.hadoop.ipc.Server).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

我还在终端中收到 RunTimeException 错误，并显示流式传输失败并且没有输出文件。

我发现一些线程说可能缺少 log4j.properties 和 log4j.xml，还有示例 log4j.properties 应该包含什么，我尝试了一个示例但没有成功。我在哪里可以找到 Hadoop 目录中的文件（如果我能找到它们）或者如何使用正确的配置创建它们？

wordcount 的 mapper 和 reducer 的代码取自 here，它运行得非常好

input.txt|./mapper.py|sort|./reducer.py

但是，我多次尝试在 hadoop 上运行它，但都失败了。当 python 文件被复制到 hdfs 以及它们在本地文件系统上时，我使用了不同的命令： 这个没用：

hadoop hadoop-streaming-2.7.1.jar -mapper /user/mapper.py -reducer /user/reducer.py -input/input_file.txt -output /user/output

也不是这个：

hadoop hadoop-streaming-2.7.1.jar -mapper "python /user/mapper.py" -reducer "python /user/reducer.py" -input/input_file.txt -output /user/output

这个确实有效（本地文件系统中的python文件）：

hadoop hadoop-streaming-2.7.1.jar -mapper "python /home/user_name/Documents/mapper.py" -reducer "python /home/user_name/Documents/reducer.py -input /user/input_file.txt -output /user/output

所有文件都有正确的权限。

标准开始后的输出如下：

16/02/15 09:47:48 INFO mapreduce.Job:  map 0% reduce 0%
16/02/15 09:48:05 INFO mapreduce.Job: Task Id : attempt_1455529218252_0001_m_000000_0, Status : FAILED
Error: java.lang.RuntimeException: Error in configuring object
    at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:112)
    at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:78)
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:136)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:449)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)
    at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
    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:1657)
    at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.reflect.InvocationTargetException
    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.util.ReflectionUtils.setJobConf(ReflectionUtils.java:109)
... 9 more
Caused by: java.lang.RuntimeException: Error in configuring object
    at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:112)
    at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:78)
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:136)
    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:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:109)
... 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 "/user/mr/mapper.py": error=2, No such file or directory
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
    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:248)
    at java.lang.ProcessImpl.start(ProcessImpl.java:134)
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
... 24 more

还有很多，但最终输出是关于流作业失败的：

16/02/15 09:49:07 INFO mapreduce.Job: Counters: 13
    Job Counters 
        Failed map tasks=7
        Killed map tasks=1
        Launched map tasks=8
        Other local map tasks=6
        Data-local map tasks=2
        Total time spent by all maps in occupied slots (ms)=135543
        Total time spent by all reduces in occupied slots (ms)=0
        Total time spent by all map tasks (ms)=135543
        Total vcore-seconds taken by all map tasks=135543
        Total megabyte-seconds taken by all map tasks=138796032
    Map-Reduce Framework
        CPU time spent (ms)=0
        Physical memory (bytes) snapshot=0
        Virtual memory (bytes) snapshot=0
16/02/15 09:49:07 ERROR streaming.StreamJob: Job not successful!
Streaming Command Failed!

从 hdfs 调用 python 代码不工作的原因是什么？

Answer 1

您应该只提供 local python 文件的名称作为-mapper 和-reducer 的参数。它们不需要在 HDFS 上，也不应该在命令行中提供一个字符串来执行脚本。

您还需要为每个脚本提供-file 参数。尝试使用

hadoop hadoop-streaming-2.7.1.jar -file /home/user_name/Documents/mapper.py -file /home/user_name/Documents/reducer.py -mapper /home/user_name/Documents/mapper.py -reducer /home/user_name/Documents/reducer.py -input /input_file.txt -output /user/output