Reland of #2264 (reverted in #2275), trimmed to buzz-relay only per review:
- Dropped all Helm chart changes (deployment.yaml, values.yaml,
values.schema.json). The worker is configured entirely via
BUZZ_GIT_GC_* env vars with safe defaults (disabled); operators can
opt in through the chart's existing relay.extraEnv. Dedicated chart
knobs can land later as a deploy-only change.
- Dropped the Hermit helm 3.16.4 pin (bin/helm) — it existed only to
lint the removed chart changes.
- Dropped the buzz-db rename (UsageMetricsLeader -> AdvisoryLockLeader).
The GC worker reuses the existing try_lock_usage_metrics(lock_key)
API with its own advisory lock key; the rename is deferred.
The opt-in worker elects one relay replica via a Postgres advisory
lock, marks objects reachable from every current repository pointer,
and inventories the shared manifests/, packs/, and idx/ namespaces,
exporting candidate counts, bytes, scan freshness, and completeness
metrics. Bounded pointer count, listed objects, manifest transfer, and
wall-clock duration. Dry-run only: nothing is ever deleted, and the
worker does not start unless BUZZ_GIT_GC_ENABLED=true.
Co-authored-by: Thomas Petersen <thomasp@squareup.com>
Signed-off-by: Thomas Petersen <thomasp@squareup.com>
