docs(ecstore): inventory replication split blockers (#4027)

crates/ecstore/src/bucket/replication/README.md

@@ -0,0 +1,49 @@
+# ECStore Replication Split Inventory
+
+This directory still belongs to ECStore. It is not ready to become a standalone
+crate because replication workers currently depend on ECStore object IO, bucket
+target clients, bucket metadata systems, runtime state, notification events,
+and lifecycle/heal scheduling paths.
+
+## Current Modules
+
+| Module | Current role | Split blocker |
+|---|---|---|
+| `config.rs` | Replication config helpers, rule matching, and tag filtering. | Uses ECStore bucket tagging helpers and S3 DTOs directly. |
+| `datatypes.rs` | Replication status and operation DTOs. | Publicly re-exported through the ECStore replication facade. |
+| `replication_pool.rs` | Replication queue, worker pool, MRF persistence, bucket stats, and delete/object scheduling. | Depends on bucket target sys, bucket metadata sys, config storage, object API, runtime sources, notification state, and storage-api object IO contracts. |
+| `replication_resyncer.rs` | Object replication, delete replication, resync, MRF encode/decode, target calls, and multipart target upload paths. | Depends on bucket target clients, metadata/versioning systems, ECStore object readers/writers, disk paths, runtime sources, notification events, and SetDisks lock timing. |
+| `replication_state.rs` | Replication queue/stat state and worker accounting. | Reads runtime sources and owns shared replication pool/stat state. |
+| `rule.rs` | Rule evaluation helpers for object replication options. | Depends on ECStore replication object option types. |
+| `mod.rs` | Compatibility re-export facade for the current ECStore owner. | Must stay stable until downstream scanner, lifecycle, heal, and metrics paths compile through replacement contracts. |
+
+## Required Contracts
+
+| Contract | Responsibility | Current dependency to remove |
+|---|---|---|
+| `ReplicationStorage` | Object read/write/delete, object walk, metadata update, and target object IO. | Direct ECStore object API and storage-api object IO coupling in worker paths. |
+| `ReplicationMetadataStore` | Replication config, bucket targets, MRF/resync state, target reset headers, and status persistence. | Direct bucket target sys, metadata sys, versioning sys, config storage, and file metadata imports. |
+| `ReplicationRuntime` | Worker pool, queue sizing, stats, bucket monitor, local node identity, cancellation, and admission state. | Direct runtime source/global access and shared replication pool/stat state. |
+| `ReplicationEventSink` | Notification and audit events for skipped, failed, pending, and completed replication operations. | Direct event notification service calls from worker code. |
+| `ReplicationLifecycleBridge` | Lifecycle-originated delete and version-purge scheduling. | Direct coupling between lifecycle worker paths and replication delete scheduling. |
+
+## Migration Rules
+
+1. Do not move `bucket/replication` into a new crate while workers import
+   bucket target sys, metadata sys, runtime sources, notification services, or
+   SetDisks lock timing directly.
+2. Keep existing queue behavior, MRF persistence, resync state, target client
+   semantics, notification/audit events, and scanner/heal classifications
+   unchanged during inventory and contract PRs.
+3. Keep the current `ReplicationStorage` trait as the starting point. Split it
+   only after call sites prove a narrower object read/write/delete/walk shape.
+4. Preserve `rustfs_ecstore::api::bucket::replication` compatibility until
+   lifecycle, scanner, OBS, heal, and tests compile through replacement paths.
+5. Move at most one contract boundary per code-bearing PR and verify it with
+   focused replication tests before broad gates.
+
+## First Code-Bearing Step
+
+Start with `ReplicationRuntime` or `ReplicationEventSink`. Both can be added as
+narrow internal contracts while keeping current queue, MRF, resync, and target
+behavior unchanged. Do not start with a crate move.

docs/architecture/ecstore-module-split-plan.md

@@ -130,6 +130,9 @@ First safe PR:
   each dependency;
 - keep global pool/stat initialization and queue behavior unchanged.
 
+The module-level inventory lives in
+`crates/ecstore/src/bucket/replication/README.md`.
+
 Focused verification for the first code-bearing replication PR:
 
 - `cargo test -p rustfs-ecstore replication --lib`