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https://issues.apache.org/jira/browse/HADOOP-5083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12668746#action_12668746
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Amar Kamat commented on HADOOP-5083:
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bq. 1. If a job is completed and retired, and then the JT as well as the
History Server restarts. Can a user get to the logs of a job that was completed
earlier?
As of now the History server simply provides a web interface for the job
history files on the history-fs. It simply reads the history file, parses it
and allows users to analyze it. JobTracker restart will make sure that
- the jobs that were marked completed will remain untouched
- the jobs that were running/pending will be completed. This also includes
maintaining the history files and making sure that in the end there is only one
history files for a completed job
bq. Does the History Server keep some sort of an persistent index into the
completed/failed jobs?
Nope. It doesnt require to keep any. All the files are maintained in a
job-history folder.
> Optionally a separate daemon should serve JobHistory
> ----------------------------------------------------
>
> Key: HADOOP-5083
> URL: https://issues.apache.org/jira/browse/HADOOP-5083
> Project: Hadoop Core
> Issue Type: Improvement
> Components: mapred
> Reporter: Arun C Murthy
> Assignee: Amar Kamat
> Attachments: HADOOP-5083-v1.2.patch, HADOOP-5083-v1.9.patch
>
>
> Currently the JobTracker serves the JobHistory to end-users off files
> local-disk/hdfs. While running very large clusters with a large user-base
> might result in lots of traffic for job-history which needlessly taxes the
> JobTracker. The proposal is to have an optional daemon which handles serving
> of job-history requests.
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