Startup warm-up, opening the switcher and the refresh button can all probe at
once, and a relay host working through tunnel retries takes an order of
magnitude longer than a loopback one — so a slow older run landed last and
replaced a fresh "ok" with its own stale "unreachable". Each host now records
which run owns its status; a status from the switch flow outranks any probe
still running for it.
Each relay attempt is also capped by what is left of the 15s budget rather than
the full per-request timeout, so an attempt started just under the deadline can
no longer run the whole 8s past it.
Bohdan Triapitsyn
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