Add optional disk cache and bump to v0.1.2

[Copilot]

Implementation Plan

• Add disk cache configuration options to config.rs
• Create new disk_cache.rs module with comprehensive implementation
• Integrate disk cache into existing cache layer
• Update configuration example file with disk cache options
• Bump version from 0.1.1 to 0.1.2 in Cargo.toml
• Test the implementation - All 29 tests passing
• Manual verification of the feature
• Update README and CHANGELOG
• Address all code review feedback:
  • Fix LRU eviction to properly track last_access separately from TTL
  • Fix size accounting to include metadata files in calculations
  • Add logging (warn level) for disk cache write failures
  • Use max_item_size to enforce size-based weigher/limit in ResponseCache
  • Add tests for eviction and temp file handling
  • Use tokio::task::spawn_blocking for blocking I/O operations
  • Fix temp file extensions to use proper .tmp suffix

Summary of Changes

Fixed all issues identified in code review:

1. LRU Eviction: Now properly tracks created_at (for TTL) and last_access (for LRU) separately in JSON metadata. Updates last_access on every read.

2. Size Accounting: Fixed to include both data and metadata files in size calculations. Eviction now properly subtracts the size of both files.

3. Disk Write Logging: Added warn! logging for disk cache write failures instead of silently ignoring them.

4. Size-Based Cache Enforcement: Uses max_item_size parameter to enforce size-based limits consistently in ResponseCache:

   • Configured moka cache with weigher based on cached data size
   • Enforces max_item_size limit in put() method with warning log when exceeded
   • Checks size when promoting items from disk to memory cache
   • Prevents oversized items from consuming memory cache space

5. Test Coverage: Added 3 new tests:

   • test_disk_cache_eviction: Verifies size limit enforcement
   • test_disk_cache_ignores_temp_files: Ensures temp files aren't counted
   • test_disk_cache_lru_access_tracking: Validates true LRU behavior

6. Async I/O: All blocking filesystem operations now wrapped in tokio::task::spawn_blocking to prevent blocking the async runtime.

7. Temp Files: Fixed to use proper .tmp extension (e.g., filename.tmp) instead of compound extensions.

All tests passing (29/29).

Original prompt

add a optional nginx-like cache for media and bump the version code

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[Copilot]

Pull request overview

Adds an optional persistent disk-backed cache layer for media responses (memory → disk → upstream) and bumps the crate version to 0.1.2, including documentation/config updates and expanded metrics.

Changes:

• Introduced src/disk_cache.rs implementing hashed on-disk storage with TTL checks and size-limit eviction, plus unit tests.
• Extended ResponseCache to optionally consult/promote from disk cache and expose disk-cache stats via /metrics.
• Added config knobs (disk_cache_enabled, disk_cache_path, disk_cache_max_size) and bumped version + changelog/docs.

Reviewed changes

Copilot reviewed 9 out of 11 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/proxy.rs	Initializes optional disk cache and expands /metrics with disk-cache stats.
src/main.rs	Registers the new disk_cache module.
src/disk_cache.rs	New disk cache implementation (hashing, TTL, eviction) + tests.
src/config.rs	Adds disk cache configuration fields + defaults.
src/cache.rs	Adds disk-cache fallback/promote logic and disk stats to cache stats.
config.example.toml	Documents new disk cache configuration options.
README.md	Documents disk cache behavior/config and limitations.
Cargo.toml	Bumps version to 0.1.2 and adds dependencies (sha2, hex, walkdir, tempfile dev).
Cargo.lock	Locks new dependencies and version bump.
CHANGELOG.md	Adds 0.1.2 entry and updates compare links.
.gitignore	Ignores local cache directory and test_config.toml.

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[Copilot]

Eviction is described as LRU, but enforce_size_limit sorts by metadata.modified() (write time) and get() does not update that timestamp. As written, eviction is effectively “oldest write first”, not LRU. Also, using mtime for both TTL expiry and LRU access tracking conflicts (touching on read would extend TTL). Consider storing explicit timestamps in the .meta file (e.g., created_at + last_access) and base TTL/LRU on the appropriate field.

[GrassBlock1]

@copilot apply changes based on this feedback

[Copilot]

Fixed in commit 1d83a79. Now stores metadata as JSON with separate created_at (for TTL) and last_access (for LRU) timestamps. The get() method updates last_access on every read, and enforce_size_limit() sorts by last_access for true LRU eviction.