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https://issues.apache.org/jira/browse/HADOOP-15550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16643956#comment-16643956
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Jonathan Eagles commented on HADOOP-15550:
------------------------------------------

Going ahead on the proposed plan. I have cherry-picked this commit to 
branch-3.1. Created HADOOP-15835 to gain a partial benefit of ObjectMapper 
reuse.

> Avoid static initialization of ObjectMappers
> --------------------------------------------
>
>                 Key: HADOOP-15550
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15550
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: performance
>    Affects Versions: 3.2.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>             Fix For: 3.2.0, 3.1.2
>
>         Attachments: hadoop-15550.txt, hadoop-15550.txt, hadoop-15550.txt, 
> hadoop-15550.txt, hadoop-15550.txt
>
>
> Various classes statically initialize an ObjectMapper READER instance. This 
> ends up doing a bunch of class-loading of Jackson libraries that can add up 
> to a fair amount of CPU, even if the reader ends up not being used. This is 
> particularly the case with WebHdfsFileSystem, which is class-loaded by a 
> serviceloader even when unused in a particular job. We should lazy-init these 
> members instead of doing so as a static class member.



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