python - # 失败的映射任务超出了允许的限制

Question

我正在尝试使用 Python 进行 Hadoop 流式处理。我在 here 的帮助下编写了简单的 map 和减少脚本。

map脚本如下:

#!/usr/bin/env python

import sys, urllib, re

title_re = re.compile("<title>(.*?)</title>", re.MULTILINE | re.DOTALL | re.IGNORECASE)

for line in sys.stdin:
    url = line.strip()
    match = title_re.search(urllib.urlopen(url).read())
    if match :
        print url, "\t", match.group(1).strip()

和reduce脚本如下:

#!/usr/bin/env python

from operator import itemgetter
import sys

for line in sys.stdin :
    line = line.strip()
    print line

使用 hadoop streaming jar 运行这些脚本后，map 任务完成，我可以看到它们已 100% 完成，但 reduce 作业卡在 22%，之后很长一段时间它会给出 ERROR streaming.StreamJob: Job not successful。错误:# of failed Map Tasks exceeded allowed limit. FailedCount:1。 错误。

我无法找出这背后的确切原因。

我的终端窗口如下所示:

shekhar@ubuntu:/host/Shekhar/Softwares/hadoop-1.0.0$ hadoop jar contrib/streaming/hadoop-streaming-1.0.0.jar -mapper /host/Shekhar/HadoopWorld/MultiFetch.py -reducer /host/Shekhar/HadoopWorld/reducer.py -input /host/Shekhar/HadoopWorld/urls/* -output /host/Shekhar/HadoopWorld/titles3
Warning: $HADOOP_HOME is deprecated.

packageJobJar: [/tmp/hadoop-shekhar/hadoop-unjar2709939812732871143/] [] /tmp/streamjob1176812134999992997.jar tmpDir=null
12/05/27 11:27:46 INFO util.NativeCodeLoader: Loaded the native-hadoop library
12/05/27 11:27:46 INFO mapred.FileInputFormat: Total input paths to process : 3
12/05/27 11:27:46 INFO streaming.StreamJob: getLocalDirs(): [/tmp/hadoop-shekhar/mapred/local]
12/05/27 11:27:46 INFO streaming.StreamJob: Running job: job_201205271050_0006
12/05/27 11:27:46 INFO streaming.StreamJob: To kill this job, run:
12/05/27 11:27:46 INFO streaming.StreamJob: /host/Shekhar/Softwares/hadoop-1.0.0/libexec/../bin/hadoop job  -Dmapred.job.tracker=localhost:9001 -kill job_201205271050_0006
12/05/27 11:27:46 INFO streaming.StreamJob: Tracking URL: http://localhost:50030/jobdetails.jsp?jobid=job_201205271050_0006
12/05/27 11:27:47 INFO streaming.StreamJob:  map 0%  reduce 0%
12/05/27 11:28:07 INFO streaming.StreamJob:  map 67%  reduce 0%
12/05/27 11:28:37 INFO streaming.StreamJob:  map 100%  reduce 0%
12/05/27 11:28:40 INFO streaming.StreamJob:  map 100%  reduce 11%
12/05/27 11:28:49 INFO streaming.StreamJob:  map 100%  reduce 22%
12/05/27 11:31:35 INFO streaming.StreamJob:  map 67%  reduce 22%
12/05/27 11:31:44 INFO streaming.StreamJob:  map 100%  reduce 22%
12/05/27 11:34:52 INFO streaming.StreamJob:  map 67%  reduce 22%
12/05/27 11:35:01 INFO streaming.StreamJob:  map 100%  reduce 22%
12/05/27 11:38:11 INFO streaming.StreamJob:  map 67%  reduce 22%
12/05/27 11:38:20 INFO streaming.StreamJob:  map 100%  reduce 22%
12/05/27 11:41:29 INFO streaming.StreamJob:  map 67%  reduce 22%
12/05/27 11:41:35 INFO streaming.StreamJob:  map 100%  reduce 100%
12/05/27 11:41:35 INFO streaming.StreamJob: To kill this job, run:
12/05/27 11:41:35 INFO streaming.StreamJob: /host/Shekhar/Softwares/hadoop-1.0.0/libexec/../bin/hadoop job  -Dmapred.job.tracker=localhost:9001 -kill job_201205271050_0006
12/05/27 11:41:35 INFO streaming.StreamJob: Tracking URL: http://localhost:50030/jobdetails.jsp?jobid=job_201205271050_0006
12/05/27 11:41:35 ERROR streaming.StreamJob: Job not successful. Error: # of failed Map Tasks exceeded allowed limit. FailedCount: 1. LastFailedTask: task_201205271050_0006_m_000001
12/05/27 11:41:35 INFO streaming.StreamJob: killJob...
Streaming Job Failed!

谁能帮帮我？？

编辑 工作跟踪器详细信息如下:

Hadoop job_201205271050_0006 on localhost

User: shekhar
Job Name: streamjob1176812134999992997.jar
Job File: file:/tmp/hadoop-shekhar/mapred/staging/shekhar/.staging/job_201205271050_0006/job.xml
Submit Host: ubuntu
Submit Host Address: 127.0.1.1
Job-ACLs: All users are allowed
Job Setup: Successful
Status: Failed
Failure Info:# of failed Map Tasks exceeded allowed limit. FailedCount: 1. LastFailedTask: task_201205271050_0006_m_000001
Started at: Sun May 27 11:27:46 IST 2012
Failed at: Sun May 27 11:41:35 IST 2012
Failed in: 13mins, 48sec
Job Cleanup: Successful
Black-listed TaskTrackers: 1
Kind    % Complete  Num Tasks   Pending Running Complete    Killed  Failed/Killed
Task Attempts
map 100.00%
3   0   0   2   1   4 / 0
reduce  100.00%
1   0   0   0   1   0 / 1

Answer 1

这个错误只是一个一般错误，太多的 map task 无法完成:

of failed Map Tasks exceeded allowed limit

您可以使用 EMR 控制台导航到各个 Map/Reduce 任务的日志。 然后您应该能够看到问题所在。

在我的例子中 - 当我犯了一些小错误时出现了这个错误，比如错误地设置了 Map 脚本的路径。

查看任务日志的步骤:

http://antipatterns.blogspot.nl/2013/03/amazon-emr-map-reduce-error-of-failed.html