1 /**
2 * Copyright 2003-2007 Greg Luck
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package net.sf.ehcache.management;
18
19 import net.sf.ehcache.CacheException;
20 import net.sf.ehcache.Ehcache;
21 import net.sf.ehcache.Statistics;
22
23 import javax.management.MalformedObjectNameException;
24 import javax.management.ObjectName;
25
26
27 /**
28 * A JMX CacheStatistics decorator for an ehcache Statistics class.
29 * <p/>
30 * An immutable Cache statistics implementation}
31 * <p/>
32 * This is like a value object, with the added ability to clear cache statistics on the cache.
33 * That ability does not survive any Serialization of this class. On deserialization the cache
34 * can be considered disconnected.
35 * <p/>
36 * The accuracy of these statistics are determined by the value of {#getStatisticsAccuracy()}
37 * at the time the statistic was computed. This can be changed by setting {@link net.sf.ehcache.Cache#setStatisticsAccuracy}.
38 * <p/>
39 * Because this class maintains a reference to an Ehcache, any references held to this class will precent the Ehcache
40 * from getting garbage collected.
41 *
42 * @author Greg Luck
43 * @version $Id: CacheStatistics.java 512 2007-07-10 09:18:45Z gregluck $
44 * @since 1.3
45 */
46 public class CacheStatistics implements CacheStatisticsMBean {
47
48 private static final long serialVersionUID = 8085302752781762030L;
49
50 private Ehcache ehcache;
51 private Statistics statistics;
52
53 private ObjectName objectName;
54 private long lastUpdated;
55
56 /**
57 * Constructs an object from an ehcache statistics object
58 *
59 * @param ehcache the backing ehcache
60 */
61 public CacheStatistics(Ehcache ehcache) {
62 this.ehcache = ehcache;
63 objectName = createObjectName(ehcache.getCacheManager().getName(),
64 ehcache.getName());
65 }
66
67 /**
68 * Creates an object name using the scheme "net.sf.ehcache:type=CacheStatistics,CacheManager=<cacheManagerName>,name=<cacheName>"
69 */
70 static ObjectName createObjectName(String cacheManagerName, String cacheName) {
71 ObjectName objectName;
72 try {
73 objectName = new ObjectName("net.sf.ehcache:type=CacheStatistics,CacheManager="
74 + cacheManagerName + ",name=" + cacheName);
75 } catch (MalformedObjectNameException e) {
76 throw new CacheException(e);
77 }
78 return objectName;
79 }
80
81
82 /**
83 * Accurately measuring statistics can be expensive. Returns the current accuracy setting used
84 * in the creation of these statistics.
85 *
86 * @return one of {@link Statistics#STATISTICS_ACCURACY_BEST_EFFORT}, {@link Statistics#STATISTICS_ACCURACY_GUARANTEED}, {@link Statistics#STATISTICS_ACCURACY_NONE}
87 */
88 public int getStatisticsAccuracy() {
89 updateIfNeeded();
90 return statistics.getStatisticsAccuracy();
91 }
92
93 private void updateIfNeeded() {
94 if (System.currentTimeMillis() != lastUpdated) {
95 statistics = ehcache.getStatistics();
96 lastUpdated = System.currentTimeMillis();
97 }
98 }
99
100 /**
101 * Accurately measuring statistics can be expensive. Returns the current accuracy setting.
102 * @return a human readable description of the accuracy setting. One of "None", "Best Effort" or "Guaranteed".
103 */
104 public String getStatisticsAccuracyDescription() {
105 updateIfNeeded();
106 return statistics.getStatisticsAccuracyDescription();
107 }
108
109 /**
110 * @return the name of the Ehcache, or null is there no associated cache
111 */
112 public String getAssociatedCacheName() {
113 return statistics.getAssociatedCacheName();
114 }
115
116 /**
117 * Clears the statistic counters to 0 for the associated Cache.
118 */
119 public void clearStatistics() {
120 statistics.clearStatistics();
121 }
122
123 /**
124 * The number of times a requested item was found in the cache.
125 * <p/>
126 * Warning. This statistic is recorded as a long. If the statistic is large than Integer#MAX_VALUE
127 * precision will be lost.
128 *
129 * @return the number of times a requested item was found in the cache
130 */
131 public long getCacheHits() {
132 updateIfNeeded();
133 return statistics.getCacheHits();
134 }
135
136 /**
137 * Number of times a requested item was found in the Memory Store.
138 *
139 * @return the number of times a requested item was found in memory
140 */
141 public long getInMemoryHits() {
142 updateIfNeeded();
143 return statistics.getInMemoryHits();
144 }
145
146 /**
147 * Number of times a requested item was found in the Disk Store.
148 *
149 * @return the number of times a requested item was found on Disk, or 0 if there is no disk storage configured.
150 */
151 public long getOnDiskHits() {
152 updateIfNeeded();
153 return statistics.getOnDiskHits();
154 }
155
156 /**
157 * Warning. This statistic is recorded as a long. If the statistic is large than Integer#MAX_VALUE
158 * precision will be lost.
159 *
160 * @return the number of times a requested element was not found in the cache
161 */
162 public long getCacheMisses() {
163 updateIfNeeded();
164 return statistics.getCacheMisses();
165
166 }
167
168 /**
169 * Gets the number of elements stored in the cache. Caclulating this can be expensive. Accordingly,
170 * this method will return three different values, depending on the statistics accuracy setting.
171 * <h3>Best Effort Size</h3>
172 * This result is returned when the statistics accuracy setting is {@link net.sf.ehcache.Statistics#STATISTICS_ACCURACY_BEST_EFFORT}.
173 * <p/>
174 * The size is the number of {@link net.sf.ehcache.Element}s in the {@link net.sf.ehcache.store.MemoryStore} plus
175 * the number of {@link net.sf.ehcache.Element}s in the {@link net.sf.ehcache.store.DiskStore}.
176 * <p/>
177 * This number is the actual number of elements, including expired elements that have
178 * not been removed. Any duplicates between stores are accounted for.
179 * <p/>
180 * Expired elements are removed from the the memory store when
181 * getting an expired element, or when attempting to spool an expired element to
182 * disk.
183 * <p/>
184 * Expired elements are removed from the disk store when getting an expired element,
185 * or when the expiry thread runs, which is once every five minutes.
186 * <p/>
187 * <h3>Guaranteed Accuracy Size</h3>
188 * This result is returned when the statistics accuracy setting is {@link net.sf.ehcache.Statistics#STATISTICS_ACCURACY_GUARANTEED}.
189 * <p/>
190 * This method accounts for elements which might be expired or duplicated between stores. It take approximately
191 * 200ms per 1000 elements to execute.
192 * <h3>Fast but non-accurate Size</h3>
193 * This result is returned when the statistics accuracy setting is {@link Statistics#STATISTICS_ACCURACY_NONE}.
194 * <p/>
195 * The number given may contain expired elements. In addition if the DiskStore is used it may contain some double
196 * counting of elements. It takes 6ms for 1000 elements to execute. Time to execute is O(log n). 50,000 elements take
197 * 36ms.
198 *
199 * @return the number of elements in the ehcache, with a varying degree of accuracy, depending on accuracy setting.
200 */
201 public long getObjectCount() {
202 updateIfNeeded();
203 return statistics.getObjectCount();
204 }
205
206
207 /**
208 * @return the object name for this MBean
209 */
210 ObjectName getObjectName() {
211 return objectName;
212 }
213
214 }