No information of unfinished map task in Job History, if all attempts of
another map task fail.
-----------------------------------------------------------------------------------------------
Key: MAPREDUCE-3926
URL: https://issues.apache.org/jira/browse/MAPREDUCE-3926
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: jobtracker
Affects Versions: 0.20.205.0
Reporter: Mitesh Singh Jat
Priority: Minor
No information of unfinished map task in Job History, if all attempts of
another map task fail.
For example,
1. The first map task's first attempt m_000000_0 was making progress
2. The second map task failed 4 times, before completion of first map task
attempt.
3. Hence, a job cleanup task was launched and completed, before completion of
first map task attempt.
4. After job cleanup task, runningMapCache is cleaned
{noformat}
completedTask() -> jobComplete() -> garbageCollect() -> this.runningMapCache =
null;
|-----> retireMap() -> if (runningMapCache == null) "Running cache
for maps missing!! Job details are missing."
{noformat}
5. Hence, "Running cache for maps missing!! Job details are missing." error
comes
(from retireMap() which is called after jobComplete() ) and no information is
added further to Job History. Therefore, first map task's information is
missing from Job History page.
I have created a sample streaming MR job, to reproduce this issue.
{code:title=mapper.sh}
#!/bin/bash
read line
if [[ "$line" == "sleep" ]]
then
for i in 1 2 3
do
echo "Sleeping" >&2
sleep 5
done
exit 0
else
echo "Exiting" >&2
exit -1
fi
{code}
Input file: in1.txt is for long running map task (here first map task)
{code:title=/user/mitesh/input/in1.txt}
sleep
{code}
Input file: in2.txt is for failing map task (here second map task)
{code:title=/user/mitesh/input/in2.txt}
exit
{code}
Running the sample streaming MR job.
{noformat}
$ hadoop fs -rmr -skipTrash xyz
$ hadoop fs -jar $HADOOP_INSTALL/hadoop-streaming.jar
-Dmapred.map.max.attempts=2 -Dmapred.min.split.size=7 -Dmapred.map.tasks=2
-mapper "mapper.sh" -file mapper.sh -reducer NONE -input
/user/mitesh/input/in1.txt -input /user/mitesh/input/in2.txt -output xyz
{noformat}
Job History web UI
{noformat}
Hadoop Job job_201201310454_542302 on History Viewer
User: mitesh
JobName: streamjob7439640883203077520.jar
JobConf: hdfs://nn:port/user/mitesh/.staging/job_201201310454_542302/job.xml
Job-ACLs:
mapreduce.job.acl-view-job: No users are allowed
mapreduce.job.acl-modify-job: No users are allowed
Submitted At: 27-Feb-2012 12:56:02
Launched At: 27-Feb-2012 12:56:11 (8sec)
Finished At: 27-Feb-2012 12:56:31 (20sec)
Status: FAILED
Failure Info: # of failed Map Tasks exceeded allowed limit. FailedCount: 1.
LastFailedTask: task_201201310454_542302_m_000001
Analyse This Job
Kind Total Tasks(successful+failed+killed) Successful tasks Failed
tasks Killed tasks Start Time Finish Time
Setup 1 1 0 0 27-Feb-2012 12:56:12 27-Feb-2012
12:56:16 (4sec)
Map 2 0 2 0 27-Feb-2012 12:56:16 27-Feb-2012
12:56:26 (10sec)
Reduce 0 0 0 0
Cleanup 1 1 0 0 27-Feb-2012 12:56:26
27-Feb-2012 12:56:31 (4sec)
{noformat}
Above it shows, only 2 failed tasks (belong to second map task).
Only from JT logs, the task tracker of first map task can be found.
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