rustfs/docs/architecture/obs-ecstore-dependency-inventory.md

Observability ECStore Dependency Inventory

Use this when: adding, removing, or moving any rustfs_ecstore or rustfs_storage_api reference inside crates/obs. Source of truth: the use block at the top of crates/obs/src/metrics/storage_api.rs; the guard in scripts/check_architecture_migration_rules.sh.

rustfs-obs still depends on rustfs-ecstore (crates/obs/Cargo.toml). Every direct reference is confined to one boundary file so the dependency can later be replaced by provider traits without touching collectors.

Dependency Inventory

The authoritative list is the pub(crate) use rustfs_ecstore::api::... block in crates/obs/src/metrics/storage_api.rs; it is not copied here. Each import belongs to one of three coupling categories:

Category	Covers	Examples (aliases defined in the boundary file)
Type coupling	Concrete ECStore types and storage-api traits used for method resolution	ObsStore, ObsEcstoreResult, ObsBucketBandwidthMonitor, the rustfs_storage_api trait imports
Runtime handle coupling	Resolving process-wide handles for metric collection	object-store handle, bucket monitor, expiry and transition state handles (rustfs_ecstore::api::runtime::*), replication stats read inside the snapshot helpers
Behavior coupling	ECStore-owned computations whose output is projected into obs-local DTOs	data-usage loading, compression totals, quota lookup, usable-capacity math

Collectors consume only the aliases and the obs-local DTOs. Removing rustfs-ecstore from crates/obs/Cargo.toml is unsafe until all three categories have replacement contracts and compile coverage.

Extraction Plan

1. Keep all direct ECStore and storage-api imports centralized in crates/obs/src/metrics/storage_api.rs.
2. Keep projecting ECStore data-usage and replication stats into obs-local DTOs before collectors consume them.
3. Introduce obs-owned provider traits for storage info, bucket info, quota, data usage, replication, bandwidth, and lifecycle queue snapshots.
4. Implement those traits in ECStore or an ECStore-owned adapter crate once the trait shapes are covered by focused tests.
5. Remove the rustfs-ecstore dependency from rustfs-obs only after metrics behavior is unchanged through the provider traits.

Guardrails

Enforced by scripts/check_architecture_migration_rules.sh:

• crates/obs/src/metrics/storage_api.rs is the only rustfs-obs source file allowed to reference rustfs_ecstore or rustfs_storage_api.
• Raw replication stats handles and ECStore replication stat methods stay behind the snapshot helpers in that file.
• rustfs-obs must not add passthrough bridge modules (a second storage_api.rs, an ecstore_compat.rs, or similar) that re-export ECStore items to other crates.
• An extraction PR that removes a dependency category updates this inventory and the guard in the same change.