| /* |
| * 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.cassandra.utils.concurrent; |
| |
| import java.util.Collection; |
| import java.util.Iterator; |
| import java.util.Objects; |
| import java.util.concurrent.BlockingQueue; |
| import java.util.concurrent.LinkedBlockingQueue; |
| import java.util.concurrent.Semaphore; |
| import java.util.concurrent.TimeUnit; |
| |
| import com.google.common.base.Preconditions; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Weighted queue is a wrapper around any blocking queue that turns it into a blocking weighted queue. The queue |
| * will weigh each element being added and removed. Adding to the queue is blocked if adding would violate |
| * the weight bound. |
| * |
| * If an element weighs in at larger than the capacity of the queue then exactly one such element will be allowed |
| * into the queue at a time. |
| * |
| * If the weight of an object changes after it is added you are going to have a bad time. Checking weight should be |
| * cheap so memoize expensive to compute weights. If weight throws that can also result in leaked permits so it's |
| * always a good idea to memoize weight so it doesn't throw. |
| * |
| * In the interests of not writing unit tests for methods no one uses there is a lot of UnsupportedOperationException. |
| * If you need them then add them and add proper unit tests to WeightedQueueTest. "Good" tests. 100% coverage including |
| * exception paths and resource leaks. |
| **/ |
| public class WeightedQueue<T> implements BlockingQueue<T> |
| { |
| private static final Logger logger = LoggerFactory.getLogger(WeightedQueue.class); |
| public static final Weigher NATURAL_WEIGHER = (Weigher<Object>) weighable -> |
| { |
| if (weighable instanceof Weighable) |
| { |
| return ((Weighable)weighable).weight(); |
| } |
| return 1; |
| }; |
| |
| private final Weigher<T> weigher; |
| private final BlockingQueue<T> queue; |
| private final int maxWeight; |
| final Semaphore availableWeight; |
| |
| public boolean add(T e) |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public boolean offer(T t) |
| { |
| Preconditions.checkNotNull(t); |
| boolean acquired = tryAcquireWeight(t); |
| if (acquired) |
| { |
| boolean offered = false; |
| try |
| { |
| offered = queue.offer(t); |
| return offered; |
| } |
| finally |
| { |
| if (!offered) |
| { |
| releaseWeight(t); |
| } |
| } |
| } |
| return false; |
| } |
| |
| public T remove() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public T poll() |
| { |
| T retval = queue.poll(); |
| releaseWeight(retval); |
| return retval; |
| } |
| |
| public T element() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public T peek() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public void put(T t) throws InterruptedException |
| { |
| Preconditions.checkNotNull(t); |
| acquireWeight(t, 0, null); |
| boolean put = false; |
| try |
| { |
| queue.put(t); |
| put = true; |
| } |
| finally |
| { |
| if (!put) |
| { |
| releaseWeight(t); |
| } |
| } |
| } |
| |
| public boolean offer(T t, long timeout, TimeUnit unit) throws InterruptedException |
| { |
| Preconditions.checkNotNull(t); |
| Preconditions.checkNotNull(unit); |
| boolean acquired = acquireWeight(t, timeout, unit); |
| if (acquired) |
| { |
| boolean offered = false; |
| try |
| { |
| offered = queue.offer(t, timeout, unit); |
| return offered; |
| } |
| finally |
| { |
| if (!offered) |
| { |
| releaseWeight(t); |
| } |
| } |
| } |
| return false; |
| } |
| |
| public T take() throws InterruptedException |
| { |
| T retval = queue.take(); |
| releaseWeight(retval); |
| return retval; |
| } |
| |
| public T poll(long timeout, TimeUnit unit) throws InterruptedException |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public int remainingCapacity() |
| { |
| throw new UnsupportedOperationException("Seems like a bad idea"); |
| } |
| |
| public boolean remove(Object o) |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public boolean containsAll(Collection<?> c) |
| { |
| throw new UnsupportedOperationException("Seems like a bad idea"); |
| } |
| |
| public boolean addAll(Collection<? extends T> c) |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public boolean removeAll(Collection<?> c) |
| { |
| throw new UnsupportedOperationException("Seems like a bad idea"); |
| } |
| |
| public boolean retainAll(Collection<?> c) |
| { |
| throw new UnsupportedOperationException("Seems like a bad idea"); |
| } |
| |
| public void clear() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public int size() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public boolean isEmpty() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public boolean contains(Object o) |
| { |
| throw new UnsupportedOperationException("Seems like a bad idea"); |
| } |
| |
| public Iterator<T> iterator() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public Object[] toArray() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public <T1> T1[] toArray(T1[] a) |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public int drainTo(Collection<? super T> c) |
| { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public int drainTo(Collection<? super T> c, int maxElements) |
| { |
| int count = 0; |
| T o; |
| while(count < maxElements && (o = poll()) != null) |
| { |
| c.add(o); |
| count++; |
| } |
| return count; |
| } |
| |
| public interface Weigher<T> |
| { |
| int weigh(T weighable); |
| } |
| |
| public interface Weighable |
| { |
| int weight(); |
| } |
| |
| public WeightedQueue(int maxWeight) |
| { |
| this(maxWeight, new LinkedBlockingQueue<T>(), NATURAL_WEIGHER); |
| } |
| |
| public WeightedQueue(int maxWeight, BlockingQueue<T> queue, Weigher<T> weigher) |
| { |
| Preconditions.checkNotNull(queue); |
| Preconditions.checkNotNull(weigher); |
| Preconditions.checkArgument(maxWeight > 0); |
| this.maxWeight = maxWeight; |
| this.queue = queue; |
| this.weigher = weigher; |
| availableWeight = new Semaphore(maxWeight); |
| } |
| |
| boolean acquireWeight(T weighable, long timeout, TimeUnit unit) throws InterruptedException |
| { |
| int weight = weigher.weigh(weighable); |
| if (weight < 1) |
| { |
| throw new IllegalArgumentException(String.format("Weighable: \"%s\" had illegal weight %d", Objects.toString(weighable), weight)); |
| } |
| |
| //Allow exactly one overweight element |
| weight = Math.min(maxWeight, weight); |
| |
| if (unit != null) |
| { |
| return availableWeight.tryAcquire(weight, timeout, unit); |
| } |
| else |
| { |
| availableWeight.acquire(weight); |
| return true; |
| } |
| } |
| |
| boolean tryAcquireWeight(T weighable) |
| { |
| int weight = weigher.weigh(weighable); |
| if (weight < 1) |
| { |
| throw new IllegalArgumentException(String.format("Weighable: \"%s\" had illegal weight %d", Objects.toString(weighable), weight)); |
| } |
| |
| //Allow exactly one overweight element |
| weight = Math.min(maxWeight, weight); |
| |
| return availableWeight.tryAcquire(weight); |
| } |
| |
| void releaseWeight(T weighable) |
| { |
| if (weighable == null) |
| { |
| return; |
| } |
| |
| int weight = weigher.weigh(weighable); |
| if (weight < 1) |
| { |
| throw new IllegalArgumentException(String.format("Weighable: \"%s\" had illegal weight %d", Objects.toString(weighable), weight)); |
| } |
| |
| //Allow exactly one overweight element |
| weight = Math.min(maxWeight, weight); |
| |
| availableWeight.release(weight); |
| } |
| } |