[HDFS-15931] Fix non-static inner classes for better memory management

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.3.1, 3.4.0
• Fix Version/s: 3.3.1, 3.4.0, 2.10.2, 3.2.3
• Component/s: hdfs
• Labels: pull-request-available
• Target Version/s: 3.3.1, 3.4.0, 3.2.3
• Hadoop Flags: Reviewed
• Assignee: Viraj Jasani
• Reporter: Viraj Jasani
• Created: 29/Mar/21 06:29
• Updated: 27/Jan/24 02:49
• Resolved: 02/Apr/21 01:27

Description

If an inner class does not need to reference its enclosing instance, it can be static. This prevents a common cause of memory leaks and uses less memory per instance of the enclosing class.
Came across DataNodeProperties as a non static inner class defined in MiniDFSCluster without holding any implicit reference to MiniDFSCluster. Taking this opportunity to find other non-static inner classes that are not holding implicit reference to their respective enclosing instances.

Issue Links

• links to: GitHub Pull Request #2830