1 package org.apache.helix.model;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.util.ArrayList;
23 import java.util.List;
24
25 import org.apache.helix.HelixProperty;
26 import org.apache.helix.ZNRecord;
27
28
29 public class LeaderHistory extends HelixProperty
30 {
31 private final static int HISTORY_SIZE = 8;
32
33 public LeaderHistory(String id)
34 {
35 super(id);
36 }
37
38 public LeaderHistory(ZNRecord record)
39 {
40 super(record);
41 }
42
43 /**
44 * Save up to HISTORY_SIZE number of leaders in FIFO order
45 * @param clusterName
46 * @param instanceName
47 */
48 public void updateHistory(String clusterName, String instanceName)
49 {
50 List<String> list = _record.getListField(clusterName);
51 if (list == null)
52 {
53 list = new ArrayList<String>();
54 _record.setListField(clusterName, list);
55 }
56
57 if (list.size() == HISTORY_SIZE)
58 {
59 list.remove(0);
60 }
61 list.add(instanceName);
62 }
63
64 @Override
65 public boolean isValid()
66 {
67 return true;
68 }
69 }