com.apple.foundationdb.DirectBufferPool Maven / Gradle / Ivy
/*
* DirectBufferPool.java
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2015-2020 Apple Inc. and the FoundationDB project authors
*
* 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.
*/
package com.apple.foundationdb;
import java.nio.ByteBuffer;
import java.util.concurrent.ArrayBlockingQueue;
/**
* A singleton that manages a pool of {@link DirectByteBuffer}, that will be
* shared by the {@link DirectBufferIterator} instances. It is responsibilty of
* user to return the borrowed buffers.
*/
class DirectBufferPool {
static final DirectBufferPool __instance = new DirectBufferPool();
// When tuning this, make sure that the size of the buffer,
// is always greater than the maximum size KV allowed by FDB.
// Current limits is :
// 10kB for key + 100kB for value + 1 int for count + 1 int for more + 2 int for KV size
static public final int MIN_BUFFER_SIZE = (10 + 100) * 1000 + Integer.BYTES * 4;
static private final int DEFAULT_NUM_BUFFERS = 128;
static private final int DEFAULT_BUFFER_SIZE = 1024 * 512;
private ArrayBlockingQueue buffers;
private int currentBufferCapacity;
public DirectBufferPool() {
resize(DEFAULT_NUM_BUFFERS, DEFAULT_BUFFER_SIZE);
}
public static DirectBufferPool getInstance() {
return __instance;
}
/**
* Resizes buffer pool with given capacity and buffer size. Throws OutOfMemory exception
* if unable to allocate as asked.
*/
public synchronized void resize(int newPoolSize, int bufferSize) {
if (bufferSize < MIN_BUFFER_SIZE) {
throw new IllegalArgumentException("'bufferSize' must be at-least: " + MIN_BUFFER_SIZE + " bytes");
}
buffers = new ArrayBlockingQueue<>(newPoolSize);
currentBufferCapacity = bufferSize;
while (buffers.size() < newPoolSize) {
ByteBuffer buffer = ByteBuffer.allocateDirect(bufferSize);
buffers.add(buffer);
}
}
/**
* Requests a {@link DirectByteBuffer} from our pool. Returns null if pool is empty.
*/
public synchronized ByteBuffer poll() {
return buffers.poll();
}
/**
* Returns the {@link DirectByteBuffer} that was borrowed from our pool.
*/
public synchronized void add(ByteBuffer buffer) {
if (buffer.capacity() != currentBufferCapacity) {
// This can happen when a resize is called while there are outstanding requests,
// older buffers will be returned eventually.
return;
}
buffers.offer(buffer);
}
}