phase3-update-summary.md

Implementation Plan Update Summary

Changes Made

Updated the BBolt registry backend implementation plan to include Phase 3: Incremental GC Optimization.

Three-Phase Approach

Phase 1: BBolt Backend (5-9 days)

• Basic bbolt backend with full-scan GC
• Suitable for registries < 100K entries
• GC time: ~1-2 seconds for 100K entries, ~7-13 seconds for 1M entries

Phase 2: In-Memory Cache (4-5 days)

• Two-layer caching system
• Full-scan GC for both cache and disk
• Performance improvement for hot data

Phase 3: Incremental GC (4-5 days)

• Batch-based incremental scanning
• Cursor tracking across GC cycles
• Adaptive strategy (auto-selects based on registry size)
• Performance: ~0.5 seconds per 50K batch (vs 7-13s for 1M full scan)
• Scalable to 10M+ entries

New Configuration Parameters

filebeat.registry:
  type: bbolt
  bbolt:
    disk_ttl: 30d
    cache_ttl: 1h
    gc_batch_size: 50000  # NEW: Entries per GC cycle

New Files Added (Phase 3)

• gc_incremental.go - Incremental GC implementation
• gc_adaptive.go - Adaptive GC strategy selector

Key Additions

1. Incremental GC Algorithm

   • Cursor-based scanning
   • Configurable batch size (default: 50K)
   • Wrap-around logic when reaching end
   • Full cycle tracking and logging

2. Adaptive Strategy

   • Auto-selects GC method based on registry size
   • < 100K entries: full scan (simpler, fast enough)
   • > 100K entries: incremental scan (scalable)

3. Performance Metrics

   • GC duration logging
   • Entries scanned/deleted tracking
   • Full cycle completion reporting

4. Cache Incremental GC

   • Snapshot-based scanning for in-memory cache
   • Batch processing of cache entries
   • Position tracking

Timeline Impact

• Previous total: 9-14 days
• New total: 13-19 days
• Phase 3 is optional - can be deferred if registries remain small

Decision Rationale

Phase 3 addresses scalability concerns for large registries (1M+ entries) while keeping Phase 1 & 2 simple. The incremental GC:

• Reduces GC pause time from 7-13s to ~0.5s per batch
• Enables horizontal scalability
• Provides smooth, predictable performance
• Can be enabled/disabled via configuration

Documentation Updates

• GC performance analysis section added
• Configuration examples updated
• Sizing guidelines documented
• Success criteria expanded
• Timeline adjusted