org.elasticsearch.common.util.concurrent.ResizableBlockingQueue Maven / Gradle / Ivy
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.util.concurrent;
import java.util.concurrent.BlockingQueue;
/**
* Extends the {@code SizeBlockingQueue} to add the {@code adjustCapacity} method, which will adjust
* the capacity by a certain amount towards a maximum or minimum.
*/
final class ResizableBlockingQueue extends SizeBlockingQueue {
private volatile int capacity;
ResizableBlockingQueue(BlockingQueue queue, int initialCapacity) {
super(queue, initialCapacity);
this.capacity = initialCapacity;
}
@Override
public int capacity() {
return this.capacity;
}
@Override
public int remainingCapacity() {
return Math.max(0, this.capacity());
}
/** Resize the limit for the queue, returning the new size limit */
public synchronized int adjustCapacity(int optimalCapacity, int adjustmentAmount, int minCapacity, int maxCapacity) {
assert adjustmentAmount > 0 : "adjustment amount should be a positive value";
assert optimalCapacity >= 0 : "desired capacity cannot be negative";
assert minCapacity >= 0 : "cannot have min capacity smaller than 0";
assert maxCapacity >= minCapacity : "cannot have max capacity smaller than min capacity";
if (optimalCapacity == capacity) {
// Yahtzee!
return this.capacity;
}
if (optimalCapacity > capacity + adjustmentAmount) {
// adjust up
final int newCapacity = Math.min(maxCapacity, capacity + adjustmentAmount);
this.capacity = newCapacity;
return newCapacity;
} else if (optimalCapacity < capacity - adjustmentAmount) {
// adjust down
final int newCapacity = Math.max(minCapacity, capacity - adjustmentAmount);
this.capacity = newCapacity;
return newCapacity;
} else {
return this.capacity;
}
}
}