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photoncloud-monorepo/specifications/flaredb/004-multi-raft/contracts/pd.md

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Contracts: PD / Placement RPCs (Multi-Raft)

Source of truth: rdb-proto/src/pdpb.proto

Services

  • Pd
    • RegisterStore(RegisterStoreRequest) -> RegisterStoreResponse
    • GetRegion(GetRegionRequest) -> GetRegionResponse
    • ListRegions(ListRegionsRequest) -> ListRegionsResponse
    • MoveRegion(MoveRegionRequest) -> MoveRegionResponse

Messages (selected)

  • Region:

    • id: u64
    • start_key: bytes
    • end_key: bytes (empty = infinity)
    • peers: repeated u64 (store IDs)
    • leader_id: u64

  • Store:

    • id: u64
    • addr: string

  • MoveRegionRequest:

    • region_id: u64
    • from_store: u64
    • to_store: u64

Behaviors / Expectations

  • ListRegions is used at bootstrap and periodic refresh to populate routing.
  • MoveRegion directs a leader to add a replica on to_store (ConfChange Add) and, after catch-up, remove from_store (ConfChange Remove). Current implementation keeps source online; removal can be triggered separately.
  • Region key ranges returned by PD must be non-overlapping; nodes validate and fail startup on overlap.
  • Heartbeat: nodes periodically refresh routing via ListRegions (30s). A dedicated heartbeat RPC can replace this in a future phase.