public Set<TableName> getOnlineTables() {
    Set<TableName> tables = new HashSet<>();
    synchronized (this.onlineRegions) {
      for (Region region : this.onlineRegions.values()) {
        tables.add(region.getTableDescriptor().getTableName());
      }
    }
    return tables;
  }
Gets the online tables in this RS. This method looks at the in-memory onlineRegions.
@return all the online tables in this RS
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java