public int getDownloaderHeaderRequestSize() {
    return downloaderHeaderRequestSize;
  }
The distance from the chain head at which we should switch from fast, snap, or checkpoint sync
to full sync.

@return distance from the chain head at which we should switch from fast, snap or checkpoint
    sync to full sync.
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/SynchronizerConfiguration.java