Per-node runtime for On-Demand Migration (rustfs/backlog#2152): turns each
bucket's persisted config into a live SourceClient guarded by a three-state
circuit breaker, a TTL negative cache, per-key singleflight, a pull
concurrency semaphore and lock-free counters with a serializable snapshot.
- sys.rs: OnceLock singleton; `apply` installs/rebuilds/removes bucket state
(config compared by value, counters preserved across rebuilds, old
cancellation token fired); `publish` is the metadata publish-hook entry
(sync removal, spawned install, generation-ordered so a slow older install
cannot overwrite a newer one); `resolve(bucket, key)` judges module switch,
bucket state, prefix filter, client availability, negative cache, breaker.
- breaker.rs: Closed/Open/HalfOpen with fixed constants (5 failures / 30 s
window / 30 s open / 1 probe); NotFound resets, AccessDenied is neutral.
- negative_cache.rs: moka sync cache keyed by local key, ttl=0 disables.
- stats.rs: requests_total{op,outcome}, pulled_bytes/objects, pull_failures,
inflight/queue gauges, log-bucket latency histogram, last_source_error;
snake_case snapshot pinned by a golden JSON test.
- Anonymous sources surface as a typed `OdmStateError::AnonymousUnsupported`
until the shared client builder gains an anonymous mode.
- rustfs: `RUSTFS_ON_DEMAND_MIGRATION_ENABLED` module switch (default false)
published to module_switches and injected into ecstore before bucket
metadata loads; hook registered at the same point.
overtrue
851ec36d86