Circuit breaker for downstream backpressure#37
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After a run of outages (5xx / connection errors) to a service, the breaker opens and calls fail fast (CircuitOpen) for a cooldown, then a half-open probe closes or re-opens it. Stops a fleet of agents from hammering a struggling downstream. Compose it around the retry client so it counts an outage only after retries are spent. Client errors (401/403/404) are answers, not outages, and never trip it; a success resets the count; the clock is injected. 279 tests (+6), mypy --strict, ruff (whole repo), catalog freshness all green. v1.4.0. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Backpressure, from the research plan: a fleet of agents retrying into a struggling downstream makes the outage worse.
CircuitBreakerHttpClientwraps anyHttpClient(compose it around the retry client, so it counts an outage only after retries are spent):failure_thresholdconsecutive outages (5xx or connection-level errors) to a service, the breaker opens and calls fail fast withCircuitOpenforreset_afterseconds, not touching the downstream.6 new tests: opens after threshold then fails fast, half-open probe closes on success, failed probe re-opens, client errors don't trip, success resets the streak, connection-level errors trip. 279 tests, mypy --strict, ruff (whole repo), catalog-freshness green. Backward compatible; v1.4.0.