diff options
Diffstat (limited to 'appc-core/appc-common-bundle/src/main/java/org/onap/appc/pool/Pool.java')
-rw-r--r-- | appc-core/appc-common-bundle/src/main/java/org/onap/appc/pool/Pool.java | 371 |
1 files changed, 371 insertions, 0 deletions
diff --git a/appc-core/appc-common-bundle/src/main/java/org/onap/appc/pool/Pool.java b/appc-core/appc-common-bundle/src/main/java/org/onap/appc/pool/Pool.java new file mode 100644 index 000000000..1faf0fe42 --- /dev/null +++ b/appc-core/appc-common-bundle/src/main/java/org/onap/appc/pool/Pool.java @@ -0,0 +1,371 @@ +/*- + * ============LICENSE_START======================================================= + * ONAP : APPC + * ================================================================================ + * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved. + * ================================================================================ + * Copyright (C) 2017 Amdocs + * ============================================================================= + * 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.onap.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(); + } + } +} |