Fast-fails while the circuit is open. Once the cooldown has elapsed,
reserves the single post-cooldown probe by switching to a half-open state
(probeInFlight) and lets that one request through; concurrent requests
while the probe is pending fast-fail so only the probe reaches the
upstream. The probe's own success or failure clears the half-open state
(closing or re-opening the breaker) via recordCircuitSuccess /
recordCircuitFailure. The cooldown scales with the number of
consecutive failed probes (see scaledCooldownMs), so repeated
probe failures back off geometrically instead of probing at exactly one
request per configured cooldown forever.
Fast-fails while the circuit is open. Once the cooldown has elapsed, reserves the single post-cooldown probe by switching to a half-open state (
probeInFlight) and lets that one request through; concurrent requests while the probe is pending fast-fail so only the probe reaches the upstream. The probe's own success or failure clears the half-open state (closing or re-opening the breaker) via recordCircuitSuccess / recordCircuitFailure. The cooldown scales with the number of consecutive failed probes (see scaledCooldownMs), so repeated probe failures back off geometrically instead of probing at exactly one request per configured cooldown forever.