fix: avoid duplicate policy updates during scheduler cancellation#2004
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samsja
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mikasenghaas
approved these changes
Mar 12, 2026
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Summary
generate_batch()cancels the previous step'supdate_policy_taskbefore starting the next step. If that cancellation lands afterupdate_weights()has started but beforeckpt_stepis committed, the nextmaybe_update_policy()can replay the same checkpoint update.That duplicates both the weight sync and the off-policy bookkeeping for a single checkpoint step.
This PR fixes the race by:
ckpt_stepimmediately after the weight update completesstop()does not hangTesting
uv run pytest tests/unit/orchestrator/test_scheduler.py -qNote
Medium Risk
Touches async concurrency/cancellation paths for policy checkpoint updates; mistakes could cause missed updates or scheduler stalls, though changes are localized and unit-tested.
Overview
Prevents duplicate checkpoint applications in
Scheduler.maybe_update_policy()by introducing a shared, lock-guardedinflight_policy_update_taskand awaiting it viaasyncio.shield()so outer cancellation doesn’t restart the same weight sync/off-policy update.Refactors policy update logic into
_compute_next_ckpt_step()and_apply_policy_update(), commitsckpt_stepimmediately afterupdate_weights()completes, and extendsstop()to cancel any in-flight policy update task. Adds unit tests covering reuse of an in-flight update after cancellation and shutdown cancellation behavior.Written by Cursor Bugbot for commit 1392836. This will update automatically on new commits. Configure here.