Steam clients lean on Range requests. Hit/miss looked fine while downloads
still felt cold when a Range miss returned the full upstream body as 200.
Add range_cache / range_upstream metrics. HIT path already sliced 206 from
the cached full object; count range_cache there. On MISS, keep stripping
Range for the upstream fetch (full object still cached) but serve the
client's requested slice as 206 and count range_upstream.
Tests in steamcache/range_test.go cover Range HIT (local, no upstream),
Range MISS (206 + full object cached), and /metrics emission.
- Introduced coalescing logic in `coalescing.go` to handle concurrent identical upstream fetches, including a state machine and response buffering for improved performance.
- Implemented a new cache file format in `format.go`, supporting serialization and deserialization of HTTP responses, along with range request handling.
- Developed an HTTP handler in `handler.go` to manage requests, including special endpoint handling and metrics reporting.
- Added rate limiting functionality in `ratelimit.go` to control per-client and global request rates, enhancing security and performance.
- Created service management capabilities in `service.go` to define and manage cacheable services, including user-agent detection.
- Updated tests in `steamcache_test.go` to cover new functionalities, ensuring robustness and reliability across the codebase.
moss
s1d3sw1ped