[HDFS-7454] Reduce memory footprint for AclEntries in NameNode

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.7.0
• Component/s: namenode
• Target Version/s: 2.7.0
• Hadoop Flags: Reviewed
• Assignee: Vinayakumar B
• Reporter: Vinayakumar B
• Created: 28/Nov/14 10:14
• Updated: 10/Apr/15 20:29
• Resolved: 05/Dec/14 04:50

Description

HDFS-5620 indicated a GlobalAclSet containing unique AclFeature can be de-duplicated to save the memory in NameNode. However it was not implemented at that time.

This Jira re-proposes same implementation, along with de-duplication of unique AclEntry across all ACLs.

One simple usecase is:
A mapreduce user's home directory with the set of default ACLs, under which lot of other files/directories could be created when jobs is run. Here all the default ACLs of parent directory will be duplicated till the explicit delete of those ACLs. With de-duplication,only one object will be in memory for the same Entry across all ACLs of all files/directories.

Issue Links

• contains: HDFS-5620 NameNode: implement Global ACL Set as a memory optimization.
• is depended upon by: HDFS-7456 De-duplicate AclFeature instances with same AclEntries do reduce memory footprint of NameNode
• relates to: HDFS-7481 Add ACL indicator to the "Permission Denied" exception.