RustNotMC/launcher/benchmarks/release-loading.md

Shared startup release response

Startup previously fetched /releases?per_page=100 on two worker threads: one for game releases and one for updates. It now decodes that response once and parses game releases once, publishing them before older-launcher fallback lookups. Manual and four-hour update checks still request fresh data. Release page retries remain independent. Existing self-update guards still apply.

Run the committed benchmark against the actual backend implementation:

CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 CARGO_PROFILE_TEST_DEBUG=0 \
  cargo test --manifest-path launcher/Cargo.toml --locked --lib \
  backend::release_loading_tests::benchmark_shared_startup_response \
  -- --ignored --nocapture

Measured on 2026-10-14, Linux x86_64, AMD Ryzen 5 5600X, Rust 1.99.0, unoptimized Cargo test profile with debug information disabled. A shared CARGO_TARGET_DIR was used for local build reuse. Each case warms up 20 times and takes the median of 201 samples; outputs are validated for equivalence and passed to black_box.

Scenario	Before median	After median	Ratio	Fetches per startup
Serial parsing/decoding work, zero transport delay	14.701 ms	7.339 ms	2.003x	2 → 1
Concurrent startup workers, 5 ms per mock request	14.778 ms	13.642 ms	1.083x	2 → 1

The measured 201 samples make 402 mock release-list fetches before and 201 after. The concurrent case reduces elapsed time by 7.7%; the two old requests can overlap, so halving requests does not halve startup latency.

The synthetic 453,197-byte JSON contains 99 game releases (including a draft) with roughly 4 KiB of notes each and one launcher release with a platform asset. The mock fetch decodes identical bytes for each request; it does not exercise HTTP, TLS, GitHub rate limits, filesystem installation scans, GUI rendering or self-update downloads. The comparison covers backend orchestration, JSON decoding, sorting, filtering and update selection, not end-to-end launcher startup or release-build timing. Fallback timing is omitted from the benchmark and its ordering/error behavior is tested separately. No persistent cache or extra copy of the game-release vector is introduced.

Validation: 26 launcher library tests passed (benchmark ignored by default); the benchmark passed explicitly; full launcher all-target check and Clippy with -D warnings passed; root and launcher format checks and git diff --check passed. The GUI compiled but was not launched interactively.