Quantify the latency the mirror load-balancing strategy adds versus a
single-URL remote, and lock it in as a regression guard.
- selection_bench_test.go: isolates baseURLAttemptOrder / beginAttempt /
endAttempt against a zero-value Engine (no network/DB/redis), covering
single-URL, round_robin (3/8), least_conn (3/8) and the gauge inc/dec
pair, plus RunParallel variants to surface sync.Map/atomic contention.
- BENCHMARKS.md: median-of-6 results on a Ryzen 7 4700U with the raw runs
and the cache-miss-only caveat.
Headline (median of 6, ns/op): single-URL ~133; round_robin ~462 (3) /
~682 (8); least_conn ~2690 (3) / ~15200 (8). Selection runs only on
cache-miss, so cache hits pay zero.