[CASSANDRA-17267] Snapshot true size is miscalculated

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.11.13, 4.0.4, 4.1-alpha1, 4.1
• Component/s: Local/Snapshots
• Bug Category: Correctness - API / Semantic Implementation
• Severity: Normal
• Complexity: Normal
• Discovered By: Code Inspection
• Platform: All
• Since Version: 3.11.11

Source Control Link

https://github.com/apache/cassandra/commit/95a622305722889c321204c4bca68a3517a29aab

Test and Documentation Plan

note on changes.txt

• Assignee: Paulo Motta
• Reporter: Paulo Motta

Authors

Paulo Motta

Reviewers

Benjamin Lerer, Brandon Williams

• Created: 19/Jan/22 01:38
• Updated: 27/May/22 19:25
• Resolved: 14/Mar/22 20:26

Description

As far as I understand, the snapshot "size on disk" is the total size of the snapshot, while the "true size" is the (size_on_disk - size_of_live_sstables).

I created a snapshot on a 3.11 node without traffic and I expected the "true size" to be 0KB since the original sstables were still present, but this didn't seem to be the case:

$ nodetool listsnapshots
Snapshot Details:
Snapshot name Keyspace name Column family name True size Size on disk
test          ks1           tbl1               4.86 KiB  5.69 KiB

Total TrueDiskSpaceUsed: 4.86 KiB

Issue Links

• Discovered while testing: CASSANDRA-16843 List snapshots of dropped tables
• is related to: CASSANDRA-14587 Deduplicate sstables shared by multiple snapshots when computing true disk space used
• Testing discovered: CASSANDRA-17357 Snapshot true size computation does not include secondary indexes