class ReplicaMap {

  ReplicaInfo get(String bpid, Block block) {
    checkBlockPool(bpid);
    checkBlock(block);
    ReplicaInfo replicaInfo = get(bpid, block.getBlockId());
    if (replicaInfo != null &&
        block.getGenerationStamp() == replicaInfo.getGenerationStamp()) {
      return replicaInfo;
    }
    return null;
  }

    ReplicaMap(Object mutex);

}