1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
|
/*-
* ============LICENSE_START=======================================================
* openECOMP : APP-C
* ================================================================================
* Copyright (C) 2017 AT&T Intellectual Property. All rights
* reserved.
* ================================================================================
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* ============LICENSE_END=========================================================
*/
package org.openecomp.appc.pool;
import java.io.Closeable;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Deque;
import java.util.List;
import java.util.ListIterator;
import java.util.Properties;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* This class is used to manage a pool of things.
* <p>
* The class is parameterized so that the type of objects maintained in the pool is definable by some provided type.
* This type must implement the <code>Comparable</code> interface so that it can be managed in the pool.
* </p>
*
* @param <T>
* The type of element being pooled
*/
public class Pool<T extends Closeable> {
private Deque<T> free;
private List<T> allocated;
private int minPool;
private int maxPool;
private Allocator<T> allocator;
private Destructor<T> destructor;
private ReadWriteLock lock;
private AtomicBoolean drained;
private Properties properties;
/**
* Create the pool
*
* @param minPool
* The minimum size of the pool
* @param maxPool
* The maximum size of the pool, set to zero (0) for unbounded
* @throws PoolSpecificationException
* If the minimum size is less than 0, or if the max size is non-zero and less than the min size.
*/
public Pool(int minPool, int maxPool) throws PoolSpecificationException {
if (minPool < 0) {
throw new PoolSpecificationException(String.format("The minimum pool size must be a "
+ "positive value or zero, %d is not valid.", minPool));
}
if (maxPool != 0 && maxPool < minPool) {
throw new PoolSpecificationException(String.format("The maximum pool size must be a "
+ "positive value greater than the minimum size, or zero. %d is not valid.", maxPool));
}
this.minPool = minPool;
this.maxPool = maxPool;
properties = new Properties();
free = new ArrayDeque<T>();
allocated = new ArrayList<T>();
lock = new ReentrantReadWriteLock();
drained = new AtomicBoolean(false);
}
/**
* Returns the amount of objects on the free collection
*
* @return The number of objects on the free collection
*/
public int getFreeSize() {
Lock readLock = lock.readLock();
readLock.lock();
try {
return free.size();
} finally {
readLock.unlock();
}
}
/**
* Returns the value for a specified property of this pool, if defined.
*
* @param key
* The key of the desired property
* @return The value of the property, or null if not defined
*/
public String getProperty(String key) {
return properties.getProperty(key);
}
/**
* Sets the value of the specified property or replaces it if it already exists
*
* @param key
* The key of the property to be set
* @param value
* The value to set the property to
*/
public void setProperty(String key, String value) {
properties.setProperty(key, value);
}
/**
* @return The properties object for the pool
*/
public Properties getProperties() {
return properties;
}
/**
* Returns the number of objects that are currently allocated
*
* @return The allocate collection size
*/
public int getAllocatedSize() {
Lock readLock = lock.readLock();
readLock.lock();
try {
return allocated.size();
} finally {
readLock.unlock();
}
}
/**
* @return the value of allocator
*/
public Allocator<T> getAllocator() {
return allocator;
}
/**
* @param allocator
* the value for allocator
*/
public void setAllocator(Allocator<T> allocator) {
this.allocator = allocator;
}
/**
* @return the value of destructor
*/
public Destructor<T> getDestructor() {
return destructor;
}
/**
* @return the value of minPool
*/
public int getMinPool() {
return minPool;
}
/**
* @return the value of maxPool
*/
public int getMaxPool() {
return maxPool;
}
/**
* @param destructor
* the value for destructor
*/
public void setDestructor(Destructor<T> destructor) {
this.destructor = destructor;
}
/**
* Drains the pool, releasing and destroying all pooled objects, even if they are currently allocated.
*/
public void drain() {
if (drained.compareAndSet(false, true)) {
Lock writeLock = lock.writeLock();
writeLock.lock();
try {
int size = getAllocatedSize();
/*
* We can't use the "release" method call here because we are modifying the list we are iterating
*/
ListIterator<T> it = allocated.listIterator();
while (it.hasNext()) {
T obj = it.next();
it.remove();
free.addFirst(obj);
}
size = getFreeSize();
trim(size);
} finally {
writeLock.unlock();
}
}
}
/**
* Returns an indication if the pool has been drained
*
* @return True indicates that the pool has been drained. Once a pool has been drained, it can no longer be used.
*/
public boolean isDrained() {
return drained.get();
}
/**
* Reserves an object of type T from the pool for the caller and returns it
*
* @return The object of type T to be used by the caller
* @throws PoolExtensionException
* If the pool cannot be extended
* @throws PoolDrainedException
* If the caller is trying to reserve an element from a drained pool
*/
@SuppressWarnings("unchecked")
public T reserve() throws PoolExtensionException, PoolDrainedException {
if (isDrained()) {
throw new PoolDrainedException("The pool has been drained and cannot be used.");
}
T obj = null;
Lock writeLock = lock.writeLock();
writeLock.lock();
try {
int freeSize = getFreeSize();
int allocatedSize = getAllocatedSize();
if (freeSize == 0) {
if (allocatedSize == 0) {
extend(minPool == 0 ? 1 : minPool);
} else if (allocatedSize >= maxPool && maxPool > 0) {
throw new PoolExtensionException(String.format("Unable to add "
+ "more elements, pool is at maximum size of %d", maxPool));
} else {
extend(1);
}
}
obj = free.removeFirst();
allocated.add(obj);
} finally {
writeLock.unlock();
}
/*
* Now that we have the real object, lets wrap it in a dynamic proxy so that we can intercept the close call and
* just return the context to the free pool. obj.getClass().getInterfaces(). We need to find ALL interfaces that
* the object (and all superclasses) implement and have the proxy implement them too
*/
Class<?> cls = obj.getClass();
Class<?>[] array;
List<Class<?>> interfaces = new ArrayList<Class<?>>();
while (!cls.equals(Object.class)) {
array = cls.getInterfaces();
for (Class<?> item : array) {
if (!interfaces.contains(item)) {
interfaces.add(item);
}
}
cls = cls.getSuperclass();
}
array = new Class<?>[interfaces.size()];
array = interfaces.toArray(array);
return CachedElement.newInstance(this, obj, array);
}
/**
* releases the allocated object back to the free pool to be used by another request.
*
* @param obj
* The object to be returned to the pool
* @throws PoolDrainedException
* If the caller is trying to release an element to a drained pool
*/
public void release(T obj) throws PoolDrainedException {
if (isDrained()) {
throw new PoolDrainedException("The pool has been drained and cannot be used.");
}
Lock writeLock = lock.writeLock();
writeLock.lock();
try {
if (allocated.remove(obj)) {
free.addFirst(obj);
}
} finally {
writeLock.unlock();
}
}
/**
* Extend the free pool by some number of elements
*
* @param count
* The number of elements to add to the pool
* @throws PoolExtensionException
* if the pool cannot be extended because no allocator has been specified.
*/
private void extend(int count) throws PoolExtensionException {
if (allocator == null) {
throw new PoolExtensionException(String.format("Unable to extend pool "
+ "because no allocator has been specified"));
}
Lock writeLock = lock.writeLock();
writeLock.lock();
try {
for (int index = 0; index < count; index++) {
T obj = allocator.allocate(this);
if (obj == null) {
throw new PoolExtensionException(
"The allocator failed to allocate a new context to extend the pool.");
}
free.push(obj);
}
} finally {
writeLock.unlock();
}
}
/**
* Used to trim the free collection by some specified number of elements, or the free element count, whichever is
* less. The elements are removed from the end of the free element deque, thus trimming the oldest elements first.
*
* @param count
* The number of elements to trim
*/
private void trim(int count) {
Lock writeLock = lock.writeLock();
writeLock.lock();
try {
int trimCount = count;
if (getFreeSize() < count) {
trimCount = getFreeSize();
}
for (int i = 0; i < trimCount; i++) {
T obj = free.removeLast();
if (destructor != null) {
destructor.destroy(obj, this);
}
}
} finally {
writeLock.unlock();
}
}
}
|