1 /**
2 * Copyright Terracotta, Inc.
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 package info.magnolia.cache.concurrent;
17
18 import java.util.concurrent.ExecutorService;
19 import java.util.concurrent.TimeUnit;
20
21 import net.spy.memcached.OperationTimeoutException;
22
23 /**
24 * Various bits of black magic garnered from experts on the concurrency-interest@cs.oswego.edu mailing list.
25 *
26 * @author Greg Luck
27 * @version $Id: ConcurrencyUtil.java 7833 2013-07-25 01:00:20Z cschanck $
28 */
29 public final class ConcurrencyUtil {
30
31 private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_1 = 20;
32 private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_2 = 12;
33 private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_3 = 7;
34 private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_4 = 4;
35
36
37 /**
38 * Utility class therefore precent construction.
39 */
40 private ConcurrencyUtil() {
41 //noop;
42 }
43
44 /**
45 * Returns a hash code for non-null Object x.
46 * <p/>
47 * This function ensures that hashCodes that differ only by
48 * constant multiples at each bit position have a bounded
49 * number of collisions. (Doug Lea)
50 *
51 * @param object the object serving as a key
52 * @return the hash code
53 */
54 public static int hash(Object object) {
55 int h = object.hashCode();
56 h ^= (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_1) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_2);
57 return h ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_3) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_4);
58 }
59
60 /**
61 * Selects a lock for a key. The same lock is always used for a given key.
62 *
63 * @param key
64 * @return the selected lock index
65 */
66 public static int selectLock(final Object key, int numberOfLocks) {
67 int number = numberOfLocks & (numberOfLocks - 1);
68 if (number != 0) {
69 throw new IllegalStateException("Lock number must be a power of two: " + numberOfLocks);
70 }
71 if (key == null) {
72 return 0;
73 } else {
74 int hash = hash(key) & (numberOfLocks - 1);
75 return hash;
76 }
77
78 }
79
80
81 /**
82 * Properly shutdown and await pool termination for an arbitrary
83 * amount of time.
84 *
85 * @param pool Pool to shutdown
86 * @param waitSeconds Seconds to wait before throwing exception
87 * @throws net.spy.memcached.OperationTimeoutException Thrown if the pool does not shutdown in the specified time
88 */
89 public static void shutdownAndWaitForTermination(ExecutorService pool, int waitSeconds) throws OperationTimeoutException {
90 // shut it down
91 pool.shutdown();
92 try {
93 // wait, wait, wait
94 if (!pool.awaitTermination(waitSeconds, TimeUnit.SECONDS)) {
95 // things still running, nuke it
96 pool.shutdownNow();
97 // wait, wait, wai
98 if (!pool.awaitTermination(waitSeconds, TimeUnit.SECONDS)) {
99 // boo hiss, didn't shutdown
100 throw new OperationTimeoutException("Pool did not terminate");
101 }
102 }
103 } catch (InterruptedException ie) {
104 // try, try again
105 pool.shutdownNow();
106 Thread.currentThread().interrupt();
107 }
108 }
109 }