fix(kernel): stamp each start when journaled, not when its batch was elected - #577
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…elected An independent batch is elected at one instant and driven serially. A start journaled after a deterministic peer ran kept the election time, so: - its wall clock included the peer's runtime (a sleep 14 step recorded 24055ms after a 10s peer), and - its lease deadline, derived from the same stale time, was already partly spent: with the 30s default, a step started 10s late held a 20s lease, and could be judged expired while running. The dispatched lease of an llm/agent step in the same batch was shortened the same way. Stamp each start when it is appended and move its lease deadline, and its dispatch's, by the same delay. Serial execution itself is unchanged: the budget gate and stop_after tests pin it deliberately. Under a simulated clock the delay is zero, so replay is unaffected. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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📝 WalkthroughWalkthrough
ChangesStart Timing and Lease Deadlines
Estimated code review effort: 2 (Simple) | ~10 minutes Suggested reviewers: Merge Risk: 🔵 Low · up to The timing test can fail on a slow host even when the engine behaves correctly. Replace its fixed limit with a deterministic spend assertion; the engine deadline paths do not show a merge-blocking mismatch. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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| if entry.entry_type == relayflowd_core::EntryType::StepAttemptStarted { | ||
| let now_ms = self.clock.now_ms(); | ||
| let delay = now_ms.saturating_sub(entry.at_ms); | ||
| if delay > 0 { | ||
| entry.at_ms = now_ms; | ||
| if let Some(deadline) = entry.payload["lease_deadline_ms"].as_i64() { | ||
| entry.payload["lease_deadline_ms"] = | ||
| deadline.saturating_add(delay).into(); |
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🔴 Slow placement expires the step lease
When placement takes over 30 seconds, StepAttemptStarted retains a deadline calculated before placement. route_start runs before the start append and can block on routing or workspace pinning. The worker receives an expired StepDispatch lease and cannot execute the step.
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A step start is elected with a 30-second lease. The driver now adjusts that deadline using the clock before it prepares, routes, and appends the entry. route_start can call an external dispatcher's routing_decision or pin a local worktree. If either takes long enough, the start and its matching dispatch retain a deadline that has already passed when the worker receives it. The worker lease rejects an already expired deadline before starting execution.
Example: A slow deterministic peer completes at 1,000 ms; the next start is stamped at 1,000 ms with a deadline of 31,000 ms. Routing takes 31 seconds. The start is journaled and dispatched at 32,000 ms, so the worker refuses the attempt instead of receiving a fresh lease.
Recommended fix: Finish preparation and routing before taking the start's clock sample, then update both the journal payload and the matching dispatch deadline immediately before append. Account for any material time spent between append and handoff if the lease is intended to start at dispatch. Add a test with a deliberately delayed routing_decision or pinning operation.
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Fixed in 04e96886. The stamp now happens in a stamp_start helper called after route_start, immediately before the append, so a slow placement no longer eats the lease. The lease deadline and the matching dispatch deadline move by the full delay since election, placement included.
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| #[test] | ||
| fn a_start_after_a_slow_deterministic_peer_is_stamped_when_journaled() { |
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This 77-line addition grows parallel_driver.rs from 480 to 557 lines, beyond the repository's explicit 500-line design-smell threshold. Move the new timestamp/lease tests and their helper into a focused test module rather than continuing to expand this file.
AGENTS.md reference: AGENTS.md:L9-L10
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Fixed in 04e96886. The two tests moved to kernel/relayflowd/tests/late_start.rs with their own minimal dispatcher and observer. parallel_driver.rs is back to its main contents (480 lines).
| slow_done.at_ms | ||
| ); | ||
| let wallclock = quick_done.payload["spend"]["wallclock_ms"].as_i64().unwrap(); | ||
| assert!(wallclock < 300, "quick's wall clock includes slow's runtime: {wallclock}ms"); |
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On a loaded CI host, spawning and completing the true subprocess can legitimately take 300 ms or more, so this assertion can fail even when the timestamp fix is correct. The preceding ordering assertion already detects the stale-start regression; use a controlled clock for an exact wall-clock assertion instead of imposing an upper bound on host scheduling latency.
AGENTS.md reference: AGENTS.md:L11-L13
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Fixed in 04e96886. I dropped the < 300ms bound. The test now checks ordering (quick's start is not earlier than slow's completion) and structure (wallclock_ms == completed.at_ms − started.at_ms), so host load can't fail it. A simulated clock would not exercise this bug: the delay only exists when real time passes between election and append.
Mutation check at this head: forcing stamp_start to no-op (if true || delay <= 0) → both late_start tests FAILED (quick started at 1790260119791 before slow completed at 1790260120205); restored (cmp identical) → the full workspace run cargo test --workspace --no-fail-fast exits 0, 28 binaries ok.
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Inline comments:
In `@kernel/relayflowd/tests/parallel_driver.rs`:
- Around line 518-519: Replace the host-time threshold assertion in the parallel
driver test with a deterministic check that `spend.wallclock_ms` equals the
difference between the journaled timestamps of `quick_done` and `quick_start`.
Keep the spend field assertion so coverage remains.
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kernel/relayflowd/src/engine/drive.rskernel/relayflowd/tests/parallel_driver.rs
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- Stamp the start after route_start, just before the append, so a slow placement cannot hand the step a lease already partly spent. - Move the late-start tests to their own file: parallel_driver.rs had grown past the 500-line limit. - Replace the real-time wall-clock bound with an ordering and a structural check, so a loaded CI host cannot fail it spuriously. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Problem
The scheduler elects an independent batch at one instant; the drive loop then runs it serially. Each
step.attempt.startedwas built with the election-timenow_msand kept it, even when journaled after a deterministic peer had run. Found while building the observer run projection (#570). Journal of a fan-out run (fetch → {lint: sleep 10, test: sleep 14} → report), elapsed seconds per entry:Two consequences:
lease_deadline_mscomes from the same stale time. With the 30s default, a step started 10s late holds a 20s lease and can be judged expired while it is running. An llm/agent step dispatched later in the same batch gets the same shortened lease in itsStepDispatch.Change
engine/drive.rs: when a start is appended, stamp it with the current clock and move itslease_deadline_msby the delay. The batch'sDispatchfor that step/attempt moves by the same delay, so the worker and the journal agree. Lease ids are unchanged (identity, not time).Serial execution is unchanged on purpose.
deterministic_spend_and_wallclock_limit_gate_parallel_batch_startsandstop_after_one_holds_for_an_independent_deterministic_batchpin it: the budget gate re-folds between starts, and crash injection stops after one completion. Under a simulated clock the delay is zero, so deterministic replay is unaffected.Evidence
relayflowd/tests/parallel_driver.rs:a_start_after_a_slow_deterministic_peer_is_stamped_when_journaled: the start is not earlier than the peer's completion; wall clock < 300ms for a no-op after asleep 0.4peer; lease deadline − start = 30000 for both steps.a_dispatch_after_a_slow_deterministic_peer_keeps_its_full_lease:StepDispatch.lease_deadline_msequals the start entry's, and is 30000 after it.if delay > 0→if false && delay > 0):cmpidentical):test result: ok. 2 passed.sh ../ops/cargo.sh test --workspace --no-fail-fast→cargo_exit=0, 26 test binaries allok, crash-injection suites included.🤖 Generated with Claude Code
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Summary by cubic
Fixes the scheduler stamping
step.attempt.startedentries with election time even when journaled after a deterministic peer ran, so wall-clock duration and lease deadlines no longer include the peer's runtime.lease_deadline_msplus the matchingStepDispatchdeadline are extended by the delay.Written for commit 04e9688. Summary will update on new commits.