[CASSANDRA-18111] Centralize all snapshot operations to SnapshotManager and cache snapshots

• Type: Improvement
• Status: Patch Available
• Priority: Normal
• Resolution: Unresolved
• Fix Version/s: 5.x
• Component/s: Local/Snapshots
• Change Category: Performance
• Complexity: Normal
• Platform: All

Test and Documentation Plan

ci

• Assignee: Stefan Miklosovic
• Reporter: Paulo Motta

Authors

Stefan Miklosovic

Reviewers

Paulo Motta

• Created: 12/Dec/22 15:55
• Updated: 4 days ago 12:57

Description

Everytime nodetool listsnapshots is called, all data directories are scanned to find snapshots, what is inefficient.

For example, fetching the org.apache.cassandra.metrics:type=ColumnFamily,name=SnapshotsSize metric can take half a second (CASSANDRA-13338).

This improvement will also allow snapshots to be efficiently queried via virtual tables (CASSANDRA-18102).

In order to do this, we should:
a) load all snapshots from disk during initialization
b) keep a collection of snapshots on SnapshotManager
c) update the snapshots collection anytime a new snapshot is taken or cleared
d) detect when a snapshot is manually removed from disk.

Issue Links

• is related to: CASSANDRA-17588 "Total TrueDiskSpaceUsed" computation does not include manifest and schema files
• is related to: CASSANDRA-13338 JMX: EstimatedPartitionCount / SnapshotSize are expensive
• is related to: CASSANDRA-18102 Add a virtual table to list snapshots
• is related to: CASSANDRASC-94 Reduce filesystem calls while streaming SSTables
• is related to: CASSANDRA-19512 Add startup flag to load a local snapshot from disk
• relates to: CASSANDRA-18271 Centralize all snapshot operations to SnapshotManager
• links to: GitHub Pull Request #3374