import org.apache.hadoop.hbase.catalog.MetaReader.Visitor; //导入依赖的package包/类
/**
 * Initialize the region assignment snapshot by scanning the hbase:meta table
 * @throws IOException
 */
public void initialize() throws IOException {
  LOG.info("Start to scan the hbase:meta for the current region assignment " +
"snappshot");
  // TODO: at some point this code could live in the MetaReader
  Visitor v = new Visitor() {
    @Override
    public boolean visit(Result result) throws IOException {
      try {
        if (result ==  null || result.isEmpty()) return true;
        Pair<HRegionInfo, ServerName> regionAndServer =
            HRegionInfo.getHRegionInfoAndServerName(result);
        HRegionInfo hri = regionAndServer.getFirst();
        if (hri  == null) return true;
        if (hri.getTable() == null) return true;
        if (disabledTables.contains(hri.getTable())) {
          return true;
        }
        // Are we to include split parents in the list?
        if (excludeOfflinedSplitParents && hri.isSplit()) return true;
        // Add the current assignment to the snapshot
        addAssignment(hri, regionAndServer.getSecond());
        addRegion(hri);
        
        // the code below is to handle favored nodes
        byte[] favoredNodes = result.getValue(HConstants.CATALOG_FAMILY,
            FavoredNodeAssignmentHelper.FAVOREDNODES_QUALIFIER);
        if (favoredNodes == null) return true;
        // Add the favored nodes into assignment plan
        ServerName[] favoredServerList =
            FavoredNodeAssignmentHelper.getFavoredNodesList(favoredNodes);
        // Add the favored nodes into assignment plan
        existingAssignmentPlan.updateFavoredNodesMap(hri,
            Arrays.asList(favoredServerList));
        return true;
      } catch (RuntimeException e) {
        LOG.error("Catche remote exception " + e.getMessage() +
            " when processing" + result);
        throw e;
      }
    }
  };
  // Scan hbase:meta to pick up user regions
  MetaReader.fullScan(tracker, v);
  //regionToRegionServerMap = regions;
  LOG.info("Finished to scan the hbase:meta for the current region assignment" +
    "snapshot");
}