org.apache.hudi.org.apache.hadoop.hbase.io.hfile.LruCachedBlockQueue Maven / Gradle / Ivy
/**
*
* 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.hbase.io.hfile;
import org.apache.hbase.thirdparty.com.google.common.collect.MinMaxPriorityQueue;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.hadoop.hbase.io.HeapSize;
/**
* A memory-bound queue that will grow until an element brings
* total size >= maxSize. From then on, only entries that are sorted larger
* than the smallest current entry will be inserted/replaced.
*
* Use this when you want to find the largest elements (according to their
* ordering, not their heap size) that consume as close to the specified
* maxSize as possible. Default behavior is to grow just above rather than
* just below specified max.
*
*
Object used in this queue must implement {@link HeapSize} as well as
* {@link Comparable}.
*/
@InterfaceAudience.Private
public class LruCachedBlockQueue implements HeapSize {
private MinMaxPriorityQueue queue;
private long heapSize;
private long maxSize;
/**
* @param maxSize the target size of elements in the queue
* @param blockSize expected average size of blocks
*/
public LruCachedBlockQueue(long maxSize, long blockSize) {
int initialSize = (int)(maxSize / blockSize);
if(initialSize == 0) initialSize++;
queue = MinMaxPriorityQueue.expectedSize(initialSize).create();
heapSize = 0;
this.maxSize = maxSize;
}
/**
* Attempt to add the specified cached block to this queue.
*
* If the queue is smaller than the max size, or if the specified element
* is ordered before the smallest element in the queue, the element will be
* added to the queue. Otherwise, there is no side effect of this call.
* @param cb block to try to add to the queue
*/
public void add(LruCachedBlock cb) {
if(heapSize < maxSize) {
queue.add(cb);
heapSize += cb.heapSize();
} else {
LruCachedBlock head = queue.peek();
if(cb.compareTo(head) > 0) {
heapSize += cb.heapSize();
heapSize -= head.heapSize();
if(heapSize > maxSize) {
queue.poll();
} else {
heapSize += head.heapSize();
}
queue.add(cb);
}
}
}
/**
* @return The next element in this queue, or {@code null} if the queue is
* empty.
*/
public LruCachedBlock poll() {
return queue.poll();
}
/**
* @return The last element in this queue, or {@code null} if the queue is
* empty.
*/
public LruCachedBlock pollLast() {
return queue.pollLast();
}
/**
* Total size of all elements in this queue.
* @return size of all elements currently in queue, in bytes
*/
@Override
public long heapSize() {
return heapSize;
}
}