Hadoop上的python流mapreduce作業失敗-缺少log4j？

Question

我嘗試在Ubuntu 15.10上安裝的hadoop 2.7.1上運行python wordcount，但出現錯誤：

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.

另外，我在終端中收到RunTimeException錯誤，並且信息流傳輸失敗並且沒有輸出文件。

我發現一些線程說log4j.properties和log4j.xml可能丟失了，還列舉了log4j.properties應該包含的內容，我嘗試了一個例子，但沒有成功。 我在哪里可以找到Hadoop目錄中的文件（如果可以找到它們），或者如何使用正確的配置來創建它們？

從這里獲取用於mapper和reducer for wordcount的代碼，並且在

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

但是，我嘗試過幾次在hadoop上運行它，但失敗了。 當將python文件復制到hdfs以及將它們放在本地文件系統上時，我使用了不同的命令進行嘗試：此命令不起作用：

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

也不是這個：

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

這確實起作用了（本地文件系統中的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

所有文件都具有正確的權限。

在標准開始之后的輸出如下：

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

還有很多，但是最終輸出是關於流作業失敗的：

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!

從hdfs調用時python代碼不起作用的原因可能是什么？

Answer 1

您應該只提供本地 python文件的名稱作為-mapper和-reducer參數。 它們不必位於HDFS上，也不必在命令行中提供字符串來執行腳本。

您還需要為每個腳本提供一個-file參數。 嘗試使用

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