[HDFS-15539] When disallowing snapshot on a dir, throw exception if its trash root is not empty

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: hdfs
• Labels: pull-request-available
• Target Version/s: 3.3.0, 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Siyao Meng
• Reporter: Siyao Meng
• Created: 26/Aug/20 17:12
• Updated: 27/Jan/24 03:13
• Resolved: 15/Sep/20 15:17

Description

When snapshot is disallowed on a dir, getTrashRoots() won't return the trash root in that dir anymore (if any). The risk is the trash root will be left there forever.
We need to throw an exception there and prompt the user to clean up or rename the trash root if it is not empty.

Issue Links

• causes: HDFS-15689 allow/disallowSnapshot on EZ roots shouldn't fail due to trash provisioning/emptiness check
• is cloned by: HDFS-15541 Disallow making a Snapshottable directory unsnapshottable if it has no empty snapshot trash directory
• relates to: HDFS-15492 Make trash root inside each snapshottable directory
• links to: GitHub Pull Request #2258