tendermint/spec/blocksync/data_structures.md

Data structures

These are the core data structures necessary to provide the Blocksync Reactor logic.

The requester data structure is used to track the assignment of a request for a block at position height to a peer whose id equals to peerID.

type bpRequester {
  mtx          Mutex
  block        *types.Block
  height       int64
  peerID       types.nodeID
  redoChannel  chan type.nodeID //redo may send multi-time; peerId is used to identify repeat
  goBlockCh chan struct{}{}
}

Pool is a core data structure that stores last executed block (height), assignment of requests to peers (requesters), current height for each peer and number of pending requests for each peer (peers), maximum peer height, etc.

type BlockPool {
  mtx                Mutex
  requesters         map[int64]*bpRequester
  height             int64
  peers              map[p2p.ID]*bpPeer
  maxPeerHeight      int64
  numPending         int32
  store              BlockStore
  requestsChannel    chan<- BlockRequest
  errorsChannel      chan<- peerError
}

The Peer data structure stores for each peer its current height and number of pending requests sent to the peer (numPending), etc.

type bpPeer struct {
  id           p2p.ID
  height       int64
  base         int64
  numPending   int32
  timeout      *time.Timer
  didTimeout   bool
  pool          *blockPool
}

BlockRequest is an internal data structure used to denote current mapping of request for a block at some height to a peer (PeerID).

type BlockRequest {
  Height int64
  PeerID p2p.ID
}