CLOSED: pass through. Threshold of failures → OPEN. After timeout → HALF-OPEN probe.

What you're seeing

Circuit breaker fails fast when a downstream is unhealthy, sparing it and giving back faster errors.

States: CLOSED (normal), OPEN (failing, reject immediately), HALF-OPEN (one probe allowed; success → CLOSED, failure → OPEN). Used by every modern resilience library (resilience4j, Polly, Hystrix legacy).

★ KEY TAKEAWAY
Closed → Open → Half-open → Closed. Fail fast, recover gradually. Standard in resilience4j, Polly.
▶ WHAT TO TRY
  • Click Failing call 5 times — circuit trips to OPEN.
  • Click Probe to allow one test — success closes the circuit.
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