The Package Cache provides three core functional areas that work together to maintain consistency between external Git repositories and the internal cache:

Functional Areas#

Repository Synchronization#

Manages the synchronization of package repositories between external Git sources and the internal cache through:

• SyncManager: Orchestrates periodic and one-time synchronization operations
• Change Detection: Identifies additions, modifications, and deletions
• Latest Revision Tracking: Automatically identifies and labels the latest package revisions
• Condition Management: Updates repository status for visibility

For detailed architecture and process flows, see [Repository Synchronization]({{% relref "/docs/5_architecture_and_components/package-cache/functionality/repository-synchronization.md" %}}).

Caching Behavior#

Optimizes performance by storing repository data and avoiding redundant operations through:

• Cache Population: Lazy loading and version-based refresh strategies
• Cache Structure: In-memory maps with concurrency control
• Cache Consistency: Version tracking, optimistic locking, and metadata synchronization
• Performance Optimization: Lock-free reads and efficient data structures

For detailed architecture and process flows, see [Caching Behavior]({{% relref "/docs/5_architecture_and_components/package-cache/functionality/caching-behavior.md" %}}).

Cache Invalidation#

Maintains consistency with external repositories by invalidating stale data through:

• Automatic Invalidation: Background sync and version-based detection
• Manual Invalidation: User-driven one-time sync using porchctl or Repository CR update
• Invalidation Strategies: Selective deletion for package revisions
• Metadata Cleanup: Orphaned resource removal and missing metadata creation

How They Work Together#

┌─────────────────────────────────────────────────────────┐
│ Package Cache │
│ │
│ ┌──────────────────┐ ┌──────────────────┐ │
│ │ Repository │ │ Caching │ │
│ │ Synchronization │ ───> │ Behavior │ │
│ │ │ │ │ │
│ │ • SyncManager │ │ • Population │ │
│ │ • Change Detect │ │ • Structure │ │
│ │ • Latest Track │ │ • Consistency │ │
│ └──────────────────┘ └──────────────────┘ │
│ │ │ │
│ └────────┬────────────────┘ │
│ ↓ │
│ ┌──────────────────┐ │
│ │ Cache │ │
│ │ Invalidation │ │
│ │ │ │
│ │ • Auto Invalid │ │
│ │ • Manual Invld │ │
│ │ • Strategies │ │
│ └──────────────────┘ │
└─────────────────────────────────────────────────────────┘

Integration flow:

1. Repository Synchronization detects changes in Git repositories
2. Caching Behavior stores and serves the synchronized data efficiently
3. Cache Invalidation removes stale data when packages are deleted or modified

Each functional area is documented in detail on its own page with architecture diagrams, process flows, and implementation specifics.