fix(rate_limiter): re-check the backoff deadline after sleeping (close TOCTOU)#97
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fix(rate_limiter): re-check the backoff deadline after sleeping (close TOCTOU)#97gadievron wants to merge 1 commit into
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…e TOCTOU) wait_if_needed() read _backoff_until under the lock, released it, then slept for the entry-time duration. If another worker extended _backoff_until (a fresh 429 via report_rate_limit) during that sleep, this worker woke before the new deadline and issued a request into the still-active backoff window -- re-triggering the 429 storm (thundering herd). Wrap the read+sleep in a loop that re-checks _backoff_until after each sleep and keeps waiting until the deadline has actually passed. Preserves the existing contract: returns 0.0 immediately when not in backoff, and increments _total_waits once per waiting call. The loop waits as long as the backoff is genuinely active (a persistently-overloaded API) -- the intended coordinated-backoff behavior, and strictly safer than the old early-wake. Tests: tests/test_rate_limiter_deadline_recheck.py (2 cases: a deadline extended mid-sleep is honored via re-check; not-in-backoff returns 0.0 without sleeping). RED 1 failed -> GREEN 2 passed; full suite 178 passed / 63 skipped (py3.11). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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wait_if_needed() read _backoff_until under the lock, released it, then slept for the entry-time
duration. If another worker extended _backoff_until (a fresh 429 via report_rate_limit) during that
sleep, this worker woke before the new deadline and issued a request into the still-active backoff
window -- re-triggering the 429 storm (thundering herd).
Wrap the read+sleep in a loop that re-checks _backoff_until after each sleep and keeps waiting until
the deadline has actually passed. Preserves the existing contract: returns 0.0 immediately when not
in backoff, and increments _total_waits once per waiting call. The loop waits as long as the backoff
is genuinely active (a persistently-overloaded API) -- the intended coordinated-backoff behavior, and
strictly safer than the old early-wake.
Tests: tests/test_rate_limiter_deadline_recheck.py (2 cases: a deadline extended mid-sleep is honored
via re-check; not-in-backoff returns 0.0 without sleeping). RED 1 failed -> GREEN 2 passed; full suite
178 passed / 63 skipped (py3.11).
Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com