1 /*
2 * #%L
3 * wcm.io
4 * %%
5 * Copyright (C) 2015 wcm.io
6 * %%
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 * #L%
19 */
20 package io.wcm.dam.assetservice.impl.dataversion;
21
22 import com.day.cq.dam.api.DamEvent;
23
24 /**
25 * Simple strategy to generate data versions - on each DAM event a new timestamp is generated and
26 * returned as data version. Please be aware that this does not produce stable data versions
27 * across a cluster of AEM instances. It should only be used if there is only one AEM instance
28 * generating the data version, or some sort of long-stable stickyness is applied on the load balancer.
29 */
30 public class TimestampDataVersionStrategy extends DataVersionStrategy {
31
32 /**
33 * Data version strategy id for configuration persistence.
34 */
35 public static final String STRATEGY = "timestamp";
36
37 private volatile String dataVersion;
38
39 /**
40 * Generate new data version on first instantiation.
41 * @param damPath DAM root path
42 */
43 public TimestampDataVersionStrategy(String damPath) {
44 super(damPath);
45 generateNewDataVersion();
46 }
47
48 @Override
49 public void handleDamEvent(DamEvent damEvent) {
50 // generate a new data version on any DAM event affecting any of the configured paths
51 generateNewDataVersion();
52 }
53
54 @Override
55 public String getDataVersion() {
56 return dataVersion;
57 }
58
59 /**
60 * Generates a new data version based on current timestamp.
61 */
62 private void generateNewDataVersion() {
63 // use timestamp as data version. clashing of versions if two are generated at exactly the same time point
64 // is not the problem, because the data version can then be the same.
65 dataVersion = Long.toString(System.currentTimeMillis());
66 log.debug("{} - Generated new data version: {}", damPath, dataVersion);
67 }
68
69 }