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;
019
020import org.apache.yetus.audience.InterfaceAudience;
021
022/**
023 * <p>
024 * There are two modes with catalog replica support.
025 * </p>
026 * <ol>
027 * <li>HEDGED_READ - Client sends requests to the primary region first, within a configured amount
028 * of time, if there is no response coming back, client sends requests to all replica regions and
029 * takes the first response.</li>
030 * <li>LOAD_BALANCE - Client sends requests to replica regions in a round-robin mode, if results
031 * from replica regions are stale, next time, client sends requests for these stale locations to the
032 * primary region. In this mode, scan requests are load balanced across all replica regions.</li>
033 * </ol>
034 */
035@InterfaceAudience.Private
036public enum CatalogReplicaMode {
037  NONE {
038    @Override
039    public String toString() {
040      return "None";
041    }
042  },
043  HEDGED_READ {
044    @Override
045    public String toString() {
046      return "HedgedRead";
047    }
048  },
049  LOAD_BALANCE {
050    @Override
051    public String toString() {
052      return "LoadBalance";
053    }
054  };
055
056  public static CatalogReplicaMode fromString(final String value) {
057    for (CatalogReplicaMode mode : values()) {
058      if (mode.toString().equalsIgnoreCase(value)) {
059        return mode;
060      }
061    }
062    throw new IllegalArgumentException();
063  }
064}