public Map<DatanodeInfo, Long> getExcludeDNs() {
    return excludeDNsCache.asMap();
  }
Try to add a datanode to the regionserver excluding cache
@param datanodeInfo the datanode to be added to the excluded cache
@param cause        the cause that the datanode is hope to be excluded
@return True if the datanode is added to the regionserver excluding cache, false otherwise
hbase-asyncfs/src/main/java/org/apache/hadoop/hbase/io/asyncfs/monitor/ExcludeDatanodeManager.java