@InterfaceAudience.Private
  public RSRpcServices getRSRpcServices() {
    return rpcServices;
  }
Trigger a flush in the primary region replica if this region is a secondary replica. Does not
block this thread. See RegionReplicaFlushHandler for details.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java