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3 Commits

Author SHA1 Message Date
Tom Boucher
86452da7cb fix(#4070): reserve shard 1's aux-suite cost out of the LPT unit-test packer (#4072)
* test(#4070): failing-first regression for shard1 aux-suite budget imbalance

- selectShard has no way to reserve virtual weight on a bin, so the LPT
  unit-test packer cannot account for shard 1's fixed aux-suite cost
  (integration/security/install/slow all pinned to shard 1/3).
- test.yml wires no such reserve into the workflow.
- ci-test-job-timeout-budget.test.cjs's LANE_COSTS entry for job `test`
  was stale (7m12s from run 30677442953, predating the aux-suite growth);
  corrected to the real evidence cited in #4070 (13m48s / cancelled at
  ~14m51s), which now honestly fails the file's own 1.5x headroom policy
  against the current 15-minute cap.

All three are expected RED on this commit; see
.gsd/bug/fix-4070-shard1-aux-suite-budget/50-test-matrix.md.

* fix(#4070): reserve shard 1's aux-suite cost out of the LPT unit-test packer

selectShard now accepts an optional initialWeights array giving one or more
bins a virtual head start before any file is placed, so LPT converges each
bin's FINAL total (assigned weight + head start) toward equal instead of
raw assigned weight alone. test.yml wires RUN_TESTS_SHARD_RESERVE=1:77 into
the full-scope unit-test step (gated on matrix.scope == 'full', so the
unrelated windows lane is unaffected) -- 77 weight units is the empirical
conversion of the aux suites' ~220s measured fixed cost, derived against
the real tests/test-timings.json (see the diagnosis artifact for the full
computation).

Also corrects two pieces of now-stale bookkeeping this issue exposed:
- ci-test-job-timeout-budget.test.cjs's LANE_COSTS entry for job `test`
  carried a 7m12s figure that predated the aux-suite growth; corrected to
  the real pre-fix evidence (13m48s / cancelled at ~14m51s, issue #4070),
  which requires raising timeout-minutes from 15 to 21 (1.5x headroom over
  the real worst-case measurement) to satisfy the file's own policy.
- test.yml's job-header and matrix comments, which still claimed the aux
  suites cost "~1m35s combined" (they now measure ~216-224s).

Closes the gap the previous commit's failing-first tests proved: selectShard
had no reserve-capacity mechanism and test.yml wired none in.

* fix(#4070): correct the reserved-weight property bound; cover main()'s reserve bounds check

Isolated code review found a genuine gap and gsd-test's real run confirmed a real
test bug it exposed:

- The fast-check property "no shard exceeds average(+reserve) + heaviest file" was
  falsified by gsd-test itself (weights=[1,1,1], total=2, reserve=6 on bin 0):
  selectShard is correct, the BOUND was wrong. A reserve large enough that its bin
  never receives a real item stays at exactly that reserve forever -- no amount of
  routing real items elsewhere can dilute a fixed head start below itself -- so the
  true bound is max(reserve, the classic Graham term), not the Graham term alone.
  Verified the corrected bound against the exact counterexample plus 20,000
  additional random trials (zero violations) before re-running gsd-test.

- Isolated review (MAJOR): the shard-total bounds check on RUN_TESTS_SHARD_RESERVE
  and its console.error fallback in main() were untested end-to-end --
  parseShardReserve itself has no concept of the shard total, so only main()
  enforces that guard, and nothing exercised it through the subprocess seam. Added
  an E2E harness test that sets RUN_TESTS_SHARD_RESERVE to an out-of-range index
  via the real CLI, asserts the fallback warning fires, AND asserts the resulting
  file selection is byte-identical to a no-reserve control run against the same
  injected timings table -- proving the reserve was actually ignored, not just
  that a warning printed.

* chore(#4070): backfill changeset PR number

pr:0 -> pr:4072

* fix(#4070): strip leaked RUN_TESTS_SHARD_RESERVE from the harness test's child env

Real GH Actions CI on this PR (run 33288554040, ubuntu shard 2/3) failed 7
tests in the shard-partitioning describe block, all with the same symptom:
`run-tests: no tests in suite "all"` where a real file count was expected.
gsd-test's own dockerized bench run never showed this, and ubuntu shards 1/3
and 3/3 (which run the same test.yml step) passed clean -- the discrepancy is
the tell: only shard 2/3 happened to schedule this specific test FILE for
that run, and the outer CI job's own environment is where the leak lives.

Root cause: test.yml's "Run unit tests" step now sets
RUN_TESTS_SHARD_RESERVE=1:77 (this issue's own reserve mechanism) on the
OUTER job that runs `npm run test:coverage:unit:raw -- --shard N`. The
harness test file's runHarness() helper spawns run-tests.cjs as a CHILD of
that same job via `{...process.env, ...extraEnv}`, so every pre-existing
--shard test in this describe block silently inherited the ambient reserve
-- even though none of them know it exists. A reserve of 77 weight units
utterly dwarfs the ~0.3 total weight of the 9-file synthetic fixtures these
tests use (none are in the real timings table, so all fall back to the same
tiny median weight), so shard index 1 is routed zero files every time --
exactly the observed "no tests" failures, and exactly the skewed 5/4 split
observed on the shard-2 test that expected a plain 3/3/3 round-robin.

Reproduced locally end to end (set RUN_TESTS_SHARD_RESERVE=1:77, spawn the
old runHarness against a synthetic 9-file fixture, --shard 1/3 -- reproduces
the exact "no tests in suite \"all\"" stderr) and confirmed the fix (env
stripped unless a test opts in via extraEnv, as the #4070 E2E bounds-check
test already does) resolves it, before re-running gsd-test.

This is a genuine bug this PR introduced -- a new ambient env var that a
pre-existing subprocess-spawning test helper didn't know to isolate against
-- not a pre-existing flake and not resource contention.

---------

Co-authored-by: sim <sim@local>
2026-08-30 00:43:02 -04:00
sim
5039d49924 ci(#3057): shard the scoped Windows lane, the last unsharded one
The scoped Windows lane reached exactly 15m05s and was cancelled on four
consecutive shas of PR #3094. A job that exceeds timeout-minutes reports as
CANCELLED rather than FAILURE, which is why it first read as infrastructure
noise; the giveaway is that the duration equals the cap. The Required tests
rollup fans that job in, so it red-blocked merge while every other lane —
including all three sharded full-Windows shards — was green.

The trigger was a change to the shared test helper, which scopes the
install-heavy suites into the selected list. The lane normally runs about eight
minutes; with that list it does not fit. It was the only unsharded lane left in
this job, so it was the only one without headroom to absorb a large scoped
list.

Issue #869 hit this exact cliff on the sibling lane and named the durable answer
in its own follow-up: a timeout bump moves the cliff, sharding removes it.
#2952 then sharded the full lane. This finishes that work.

The runner already supports it — the shard partition is applied after scope
selection, so it composes with a selected file list rather than only with a
suite, and the partition is cost-weighted from the measured timings table. The
job name template already renders a shard suffix when one is present, so the
three entries name themselves. No individual matrix job is a required status
check; the rollup is, and it is name-independent, so renaming these jobs does
not touch branch protection.

timeout-minutes stays at 15. Each shard now does roughly a third of the work,
so the cap goes from binding to backstop without being raised.

The lane-shape tests were generalized rather than relaxed: the complete-shard-set
invariant now runs per sharded scope instead of only over the full lane, and
"only the full lane is sharded" became "targeted is the only unsharded lane". A
new assertion pins the shard through to the runner — without it the three shards
would each run the entire selected list, triple the cost and no speedup, and
every check would stay green.

No LANE_COSTS entry is added for the new shards. The only recorded cost for that
lane is the pre-sharding run that hit the cap, and inventing a post-sharding
number would be exactly the kind of unmeasured claim the rest of that table
avoids. The estimate and the reason are written down instead, to be replaced by
a real measurement.

Refs #3057

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-05 23:22:59 -04:00
Tom Boucher
f6257f3745 ci(#2952): shard the full test lane instead of widening its cap (#2960)
* ci(#2952): budget CI job timeouts by headroom over measured cost

`origin/next` was red. The only failing check was `Required tests`, and its
sole cause was `test (ubuntu-latest, 24)` reported `cancelled` — GitHub's
conclusion for a job that exceeds its `timeout-minutes`, not a button press.

That job's `ubuntu-latest / 24` entry is the only `scope: full` matrix entry:
it runs the whole unit suite under c8 coverage, then the scripts/ coverage
floor, integration, security, install and slow, serially on one runner. On
next@5a0a9f097 it ran 15m16s against `timeout-minutes: 15` and was axed 23s
into `npm run test:slow`. Projected to a completed slow step (27s on the last
green run) the lane costs ~15m20s.

Confirmed hypothesis: the budget, not the suite. The lane had been riding the
ceiling all day — 12m03s, 11m34s, 11m50s, 14m25s, 14m51s — and crossed on
three of the last four full-lane runs (d2d2f7c08, 07603df8f, 5a0a9f097). There
is no pathological test: the unit run is cost-first bin-packed into 12 chunks,
chunk 1 is gated by run-tests-harness.test.cjs at 169s (expensive by design —
it spawns real harness subprocesses, one of which exercises the per-chunk
timeout), and the remaining chunks are 32-94s. 769s is the honest cost of 689
files under c8. Re-running could not have helped; the work exceeded the budget.

Review of the first cut surfaced the same defect one runner away: `full test
(windows-latest, 22, shard 3/3)` reached 18m59s against its own 20-minute cap
on 05b170e44 (94%) and 18m14s on 81eeb8a53 (91%). That lane has already blown
its cap twice (#1051, #1212). Fixed here rather than deferred.

The first cut also asserted `test >= test-full`, which is unsound — those two
budgets are dominated by different platforms, so their ordering carries no
meaning. Replaced with the invariant that actually generalises: every lane is
held to a headroom FACTOR over its own measured cost. `test` 15 -> 25 (1.5x of
16m), `test-full` 20 -> 30 (1.5x of 19m), `test-inert` unchanged at 15.

tests/ci-test-job-timeout-budget.test.cjs locks that rule. No unit test can
prove a lane still FITS its budget — only a real run measures that — but a
budget can no longer be lowered back beneath what its lane is known to need,
and a lane that gets slower must be re-measured rather than excused.

Separately: the earlier `failure` at 05b170e44 was an unrelated, already-fixed
CONTEXT-INDEX.json drift (07603df8f re-synced it; lint-tests is green at HEAD).
07603df8f's own run hit this same timeout, which is why it never reported green.

Refs #869, #1051, #1212

* ci(#2952): shard the full test lane instead of widening its cap

The `scope: full` lane was the only unsharded lane in this file. It ran the
entire unit suite under c8 on one runner, grew past a 15-minute cap, and
reddened `next`. Raising the cap bought room; it did not change the shape, and
the same lane would have walked back into the ceiling. Shard it, the way #1212
answered this for the Windows lane.

Balance comes from measurement, not file counts. scripts/run-tests.cjs already
partitions by measured per-file duration using LPT (#2472); the table it reads
was 10 days stale — 638 of 695 files timed, 64 missing, including the whole
context-predicates group. Regenerated from a verified matrix run: 700 files, 0
missing. On that table the 685-file unit suite splits 19.37m / 19.37m / 19.37m
— 0.0% spread — and the split is a total, disjoint cover with 0 files dropped.
Completeness, disjointness, balance and determinism of the partition itself are
already pinned against selectShard in run-tests-harness.test.cjs, including a
fast-check property, so this change does not restate them.

Sharding a COVERAGE run is the part that needs care. A per-shard percentage is
meaningless — shard 2 never executes shard 1's files, so those read 0% — and
leaving the gate on the shards would have quietly measured a third of the tree.
Each shard now renders no report and only leaves raw V8 dumps; a new
`coverage-gate` job merges all three into one coverage/tmp and runs the gate
there. c8's default temp directory is where the download lands, so the ≥70%
lines / ≥60% branches gate and the ≥55% scripts floor run unmodified against
merged data.

Both surfaces call the same npm scripts rather than inlining c8 into YAML, so
the include/exclude globs and both thresholds stay defined once in package.json.
The workflow holding its own copy is the divergence this repo has a rule
against, and the new test cross-checks package.json so an inline reintroduction
fails rather than drifts.

tests/ci-full-lane-sharding.test.cjs covers the two ways this stays GREEN while
being wrong: an incomplete shard set (declare 1/3 and 2/3, never 3/3, and a
third of the suite silently stops running) and a coverage gate that stops being
required. required-tests now depends on coverage-gate and fails on it, while
still tolerating `skipped` so docs-only PRs are not blocked.

`timeout-minutes: 25` on the lane is deliberately left alone. The budget test
requires a real measurement before a lane's declared cost changes, and the
sharded cost is not measured until this PR's own CI run.

Refs #1212, #2472

* ci(#2952): tighten the sharded lane's budget to its measured cost

The sharding commit deliberately left `timeout-minutes: 25` alone, because
tests/ci-test-job-timeout-budget.test.cjs requires a real measurement before a
lane's declared cost changes and the sharded cost did not exist yet.

It exists now. Run 30677442953: shard 1/3 7m12s, 2/3 4m32s, 3/3 3m59s, and
coverage-gate 1m20s. Shard 1 is the long pole because the unsharded aux suites
ride along on it, which is deliberate — they total ~1m35s and sharding them
would cost more than it saves.

So the lane's budget is 15 against a slowest measured shard of 8 minutes
(~1.9x), and coverage-gate joins LANE_COSTS at 2 minutes. 15 is the same number
the lane blew before sharding; the work behind it is now a third the size.

Merged coverage was checked against the pre-shard single-runner baseline rather
than assumed from a green check: 94.36 stmts / 96.3 funcs / 94.36 lines
identical, branches 84.22 vs 84.21 — one branch across two different trees,
noise rather than a regression.

---------

Co-authored-by: sim <sim@local>
2026-07-31 22:16:26 -04:00