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https://issues.apache.org/jira/browse/HADOOP-15550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16640251#comment-16640251
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Jonathan Eagles commented on HADOOP-15550:
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I have some interest in back-porting this improvement to 2.8 (Mainly to get rid
of the new ObjectMapper creation for KMSJSONWriter). Seems like a simple
cherry-pick to 3.1 is possible when JsonSerialization library was added as part
of HADOOP-13786. Back-porting to earlier lines either means partial
back-porting HADOOP-13786 or creating a small KMSJSONWriter custom performance
patch to remove the ObjectMapper creation.
[[email protected]], [~tlipcon] do you have preference on this? It seems the
most straight forward to 1) back-port this jira to 3.1. and 2) Create a
separate KMSJSONWriter jira for earlier lines, but I am open to suggestions.
> 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
>
> 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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