[CASSANDRA-17102] CEP-15: (C*) Unified Commit Log

• Type: New Feature
• Status: Triage Needed
• Priority: Normal
• Resolution: Unresolved
• Component/s: Consistency/Hints, Local/Commit Log
• Epic Link: CEP-15: Cassandra Prototype
• Platform: All
• Assignee: Unassigned
• Reporter: Benedict Elliott Smith
• Created: 30/Oct/21 11:05
• Updated: 03/Feb/22 22:08

Description

Create a new data structure and system for combining Commit Log and Hints. This system will support compaction of commit log segments when the commit log is under space pressure, but under normal operation will continue to drop entire log records as soon as they become invalidated. By ensuring compaction only occurs for segments that are under 50% utilised we bound space and bandwidth at 2x optimal (and can tune this trade-off if we prefer, e.g. trading more space for less bandwidth)

This system will replace the storage layer for Commit Log and Hints, and be used to implement distributed repair for Accord (and perhaps other systems in future)