rbalamohan commented on a change in pull request #3736: URL: https://github.com/apache/hadoop/pull/3736#discussion_r760618253
########## File path: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/common/BoundedResourcePool.java ########## @@ -0,0 +1,179 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +package org.apache.hadoop.fs.common; + +import java.util.Collections; +import java.util.IdentityHashMap; +import java.util.Set; +import java.util.concurrent.ArrayBlockingQueue; + +/** + * Manages a fixed pool of resources. + * + * Avoids creating a new resource if a previously created instance is already available. + */ +public abstract class BoundedResourcePool<T> extends ResourcePool<T> { + // The size of this pool. Fixed at creation time. + private final int size; + + // Items currently available in the pool. + private ArrayBlockingQueue<T> items; + + // Items that have been created so far (regardless of whether they are currently available). + private Set<T> createdItems; + + /** + * Constructs a resource pool of the given size. + * + * @param size the size of this pool. Cannot be changed post creation. + */ + public BoundedResourcePool(int size) { + Validate.checkPositiveInteger(size, "size"); + + this.size = size; + this.items = new ArrayBlockingQueue<T>(size); + + // The created items are identified based on their object reference. + this.createdItems = Collections.newSetFromMap(new IdentityHashMap<T, Boolean>()); + } + + /** + * Acquires a resource blocking if necessary until one becomes available. + */ + @Override + public T acquire() { + return this.acquireHelper(true); + } + + /** + * Acquires a resource blocking if one is immediately available. Otherwise returns null. + */ + @Override + public T tryAcquire() { + return this.acquireHelper(false); + } + + /** + * Releases a previously acquired resource. + */ + @Override + public void release(T item) { + Validate.checkNotNull(item, "item"); + + synchronized (this.createdItems) { + if (!this.createdItems.contains(item)) { + throw new IllegalArgumentException("This item is not a part of this pool"); + } + } + + // Return if this item was released earlier. + // We cannot use this.items.contains() because that check is not based on reference equality. + for (T entry : this.items) { + if (entry == item) { + return; + } + } + + while (true) { + try { + this.items.put(item); Review comment: While loop isn't needed?. Doesn't ArrayBlockingQueue inherently wait for space to become available? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: common-issues-h...@hadoop.apache.org
