[HDFS-11911] SnapshotDiff should maintain the order of file/dir creation and deletion

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.0.0-alpha1
• Component/s: hdfs, snapshots
• Target Version/s: 3.5.0
• Assignee: Manoj Govindassamy
• Reporter: Manoj Govindassamy
• Created: 01/Jun/17 19:26
• Updated: 04/Jan/24 07:22

Description

DirectoryWithSnapshotFeature maintains a separate list for CREATED and DELETED children but the ordering of these creation and deletion events are not maintained. Assume a case like below, where the time is growing downwards...

|
+  CREATE File-1
|
+ Snap S1 created
|
+ DELETE File-1
|
+ Snap S2 created
|
+ CREATE File-1
|
+ Snap S3 created
|
|
V

The snapshot diff report which takes in the DirectoryWithSnapshotFeature diff entries and just prints all the creation first and then the deletions, thereby giving the perception that file-1 got created first and then got deleted. But after S3, file-1 is still available.

The difference between snapshot S1 and snapshot S3 under the directory /:
M	.
+	./file-1
-	./file-1

Can we have DirectoryWithSnapshotFeature maintain the diff entries ordered by time or sequence?