1 /***
2 * Copyright 2003-2010 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
17 package net.sf.ehcache.pool.impl;
18
19 import net.sf.ehcache.pool.PoolEvictor;
20 import net.sf.ehcache.pool.PoolableStore;
21
22 import java.util.ArrayList;
23 import java.util.Collection;
24
25 /***
26 * Abstract pool evictor which always evicts from the store consuming the most resources.
27 *
28 * @author Ludovic Orban
29 */
30 public abstract class AbstractFromLargestCachePoolEvictor implements PoolEvictor<PoolableStore> {
31
32 /***
33 * {@inheritDoc}
34 */
35 public boolean freeSpace(Collection<PoolableStore> from, long bytes) {
36 if (from == null || from.isEmpty()) {
37 return false;
38 }
39
40 long remainingSizeInBytes = bytes;
41 Collection<PoolableStore> tried = new ArrayList<PoolableStore>();
42
43 while (tried.size() != from.size()) {
44 PoolableStore largestPoolableStore = findUntriedLargestPoolableStore(from, tried);
45
46 long beforeEvictionSize = getSizeInBytes(largestPoolableStore);
47 if (!evict(1, bytes, largestPoolableStore)) {
48 tried.add(largestPoolableStore);
49 continue;
50 }
51 long afterEvictionSize = getSizeInBytes(largestPoolableStore);
52
53 remainingSizeInBytes -= (beforeEvictionSize - afterEvictionSize);
54 if (remainingSizeInBytes <= 0L) {
55 return true;
56 }
57 }
58
59 return false;
60 }
61
62 /***
63 * Evict from a store for a chosen resource
64 *
65 * @param count the element count
66 * @param bytes the bytes count
67 * @param poolableStore the store
68 * @return true if eviction succeeded, ie: if there was enough evictable resource held by the store
69 */
70 protected abstract boolean evict(int count, long bytes, PoolableStore poolableStore);
71
72 /***
73 * Get a store size in bytes for a chosen resource
74 *
75 * @param poolableStore the store
76 * @return the size in bytes
77 */
78 protected abstract long getSizeInBytes(PoolableStore poolableStore);
79
80 private PoolableStore findUntriedLargestPoolableStore(Collection<PoolableStore> from, Collection<PoolableStore> tried) {
81 PoolableStore largestPoolableStore = null;
82 for (PoolableStore poolableStore : from) {
83 if (alreadyTried(tried, poolableStore)) {
84 continue;
85 }
86
87 if (largestPoolableStore == null || getSizeInBytes(poolableStore) > getSizeInBytes(largestPoolableStore)) {
88 largestPoolableStore = poolableStore;
89 }
90 }
91 return largestPoolableStore;
92 }
93
94 private boolean alreadyTried(Collection<PoolableStore> tried, PoolableStore from) {
95 for (PoolableStore poolableStore : tried) {
96 if (poolableStore == from) {
97 return true;
98 }
99 }
100 return false;
101 }
102
103 }