- Add SharedStorageMonitor thread to periodically verify shared storage:
* Writes a temp file to the shared location and validates MD5 from all nodes.
* Skips nodes with unstable recent heartbeats; retries once; defers decision if any node is unreachable.
* Updates a cluster-wide stateful flag (shared_storage_on) only on conclusive checks.
- New CMAPI endpoints:
* PUT /cmapi/{ver}/cluster/check-shared-storage — orchestrates cross-node checks.
* GET /cmapi/{ver}/node/check-shared-file — validates a given file’s MD5 on a node.
* PUT /cmapi/{ver}/node/stateful-config — fast path to distribute stateful config updates.
- Introduce in-memory stateful config (AppStatefulConfig) with versioned flags (term/seq) and shared_storage_on flag:
* Broadcast via helpers.broadcast_stateful_config and enhanced broadcast_new_config.
* Config PUT is now validated with Pydantic models; supports stateful-only updates and set_mode requests.
- Failover behavior:
* NodeMonitor keeps failover inactive when shared_storage_on is false or cluster size < 3.
* Rebalancing DBRoots becomes a no-op when shared storage is OFF (safety guard).
- mcl status improvements: per-node 'state' (online/offline), better timeouts and error reporting.
- Routing/wiring: add dispatcher routes for new endpoints; add ClusterModeEnum.
- Tests: cover shared-storage monitor (unreachable nodes, HB-based skipping), node manipulation with shared storage ON/OFF, and server/config flows.
- Dependencies: add pydantic; minor cleanups and logging.
