The five internal/app partitions ran end to end inside one job, so the app
shard's wall clock was the sum of all five: 780s in CI, of which the schema
partition owned 357s. Each partition is now its own matrix shard, so they run
concurrently and the shard's wall clock is set by its slowest partition rather
than by their total. Every partition shard still selects the same single
internal/app package, so the impacted-package query maps the shard name back to
app and the partition only chooses which tests run.
The helper gains a partition argument and a list-partitions mode. APP_PARTITIONS
is the single source of truth for the set, and the discovery pass still runs in
every job, so each one independently verifies that the partition patterns cover
every top-level test exactly once before running the one it was asked for.
Two fail-closed checks guard the split, because the helper's own coverage check
can no longer prove the whole package ran once the partitions are separate jobs:
- The helper cross-checks APP_PARTITIONS against the coverage counters in both
directions, so a counted partition that nothing dispatches and a dispatchable
partition with no counter both fail instead of silently skipping tests.
- TestCIAppRacePartitionMatrixMatchesHelper pins the workflow's app-<partition>
shards to list-partitions output in both directions, so a partition cannot
lose its job while every job stays green.
The discovery loop variable is renamed from partition to spec: it would
otherwise shadow the partition requested on the command line, which run mode
reads after the discovery pass completes.
The schema partition's 52 tests assert structural Schema-to-Cobra contracts over
a single goroutine: none of them call t.Parallel or start a goroutine, so the
race detector has no concurrent access to observe there. The process-global lazy
metadata that does need race coverage (schema_source_root's atomic.Value, the
parameter-binding lazy loaders) is exercised by internal/cli's concurrent tests,
which stay instrumented.
The instrumentation was not free here. The partition shares a single sync.Once
Catalog build whose work is allocation-heavy, and -race made it roughly 11x
slower: 26s -> 291s locally, and 357s of the app shard's 780s in CI. Within that
partition TestFinalSchemaToolsHaveExecutableBaseCommands alone accounted for
262s, not because the test is expensive but because it is the first caller to pay
for the shared snapshot; its 1121 subtests together measure 0.00s.
run_partition now takes the instrumentation mode explicitly and fails closed on
an unrecognized value, so a typo cannot silently drop -race from a partition that
is supposed to carry it.
chichuan