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https://issues.apache.org/jira/browse/MAPREDUCE-6652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15314797#comment-15314797
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Robert Kanter commented on MAPREDUCE-6652:
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Looks good overall.  A few things:
- In mapred-default, let's change "-1 as the default value to disable the 
settings." to "A value of -1 (default) will allow all jobs to be loaded".
- In 
{{TestHistoryFileManager#testHistoryFileInfoLoadNormalSizedJobShouldReturnCompletedJob}}
 the comment says "set up a job of which the number of tasks is greater than 
maximum allowed".  However, the max tasks is set to "-1", as in there is no 
maximum allowed.  The comment should be corrected.
-- It would also be good to add a third test where the max tasks is set to 
something and the job has fewer tasks than the maximum so it gets loaded
- If you look at {{CompletedJob}}, it saves the {{JobReport}} so we don't make 
a new one each time {{getReport()}} is called.  While constructing the 
{{UnparsedJob}} report is cheaper than that for the {{CompletedJob}}, it's 
still probably a good idea to do this in the {{UnparsedJob}} to, to save on 
object creation.
- {{UnparsedJob#getProgress()}} should return {{1.0f}} instead of {{-1}}.  The 
job has finished, so it's at 100%.


> Add configuration property to prevent JHS from loading jobs with a task count 
> greater than X
> --------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6652
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6652
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobhistoryserver
>            Reporter: Haibo Chen
>            Assignee: Haibo Chen
>         Attachments: mapreduce6652.001.patch, mapreduce6652.002.patch, 
> mapreduce6652.003.patch, mapreduce6652.004.patch
>
>
> Jobs with large number of tasks can have job history files that are large in 
> size and resource-consuming(mainly memory) to parse in Job History Server. If 
> there are many such jobs, the job history server can very easily hang.
> It would be a good usability feature if we added a new config property that 
> could be set to X, where the JHS wouldn't load the details for a job with 
> more than X tasks. The job would still show up on the list of jobs page, but 
> clicking on it would give a warning message that the job is too big, instead 
> of actually loading the job. This way we can prevent users from loading a job 
> that's way too big for the JHS, which currently makes the JHS hang. The 
> default value can be -1 so that it's disabled.



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