[HADOOP-15550] Avoid static initialization of ObjectMappers

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.2.0
• Fix Version/s: 3.2.0, 3.1.2
• Component/s: performance
• Target Version/s: 3.2.0
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 20/Jun/18 18:56
• Updated: 09/Oct/18 19:28
• Resolved: 25/Jun/18 22:37

Description

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.

Issue Links

• relates to: HADOOP-15835 Reuse Object Mapper in KMSJSONWriter