001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.client;
019
020import org.apache.hadoop.hbase.HRegionLocation;
021import org.apache.hadoop.hbase.TableName;
022import org.apache.yetus.audience.InterfaceAudience;
023
024/**
025 * A Catalog replica selector decides which catalog replica to go for read requests when it is
026 * configured as CatalogReplicaMode.LoadBalance.
027 */
028@InterfaceAudience.Private
029interface CatalogReplicaLoadBalanceSelector {
030
031  int UNINITIALIZED_NUM_OF_REPLICAS = -1;
032
033  /**
034   * This method is called when input location is stale, i.e, when clients run into
035   * org.apache.hadoop.hbase.NotServingRegionException.
036   * @param loc stale location
037   */
038  void onError(HRegionLocation loc);
039
040  /**
041   * Select a catalog replica region where client go to loop up the input row key.
042   * @param tablename  table name
043   * @param row        key to look up
044   * @param locateType locate type
045   * @return replica id
046   */
047  int select(TableName tablename, byte[] row, RegionLocateType locateType);
048}