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https://issues.apache.org/jira/browse/HADOOP-15549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16518583#comment-16518583
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Todd Lipcon commented on HADOOP-15549:
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bq. The patch doesn't appear to include any new or modified tests. Please
justify why no new tests are needed for this patch. Also please list what
manual steps were performed to verify this patch.
Existing tests cover this code path -- just using a different set of APIs. I'm
not 100% sure the behavior didn't change, but if it did change, it probably
isn't commonly used functionality (and likely going back to what it was in
hadoop 2)
> Upgrade to commons-configuration 2.1 regresses task CPU consumption
> -------------------------------------------------------------------
>
> Key: HADOOP-15549
> URL: https://issues.apache.org/jira/browse/HADOOP-15549
> Project: Hadoop Common
> Issue Type: Bug
> Components: metrics
> Affects Versions: 3.0.2
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Major
> Attachments: hadoop-15549.txt
>
>
> HADOOP-13660 upgraded from commons-configuration 1.x to 2.x.
> commons-configuration is used when parsing the metrics configuration
> properties file. The new builder API used in the new version apparently makes
> use of a bunch of very bloated reflection and classloading nonsense to
> achieve the same goal, and this results in a regression of >100ms of CPU time
> as measured by a program which simply initializes DefaultMetricsSystem.
> This isn't a big deal for long-running daemons, but for MR tasks which might
> only run a few seconds on poorly-tuned jobs, this can be noticeable.
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