| /** |
| * 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.bookkeeper.common.util; |
| |
| import java.util.concurrent.atomic.AtomicLong; |
| import java.util.concurrent.locks.Condition; |
| import java.util.concurrent.locks.ReentrantLock; |
| |
| /** |
| * Controller for tracking the amount of memory used for some task. |
| */ |
| public class MemoryLimitController { |
| |
| private final long memoryLimit; |
| private final AtomicLong currentUsage = new AtomicLong(); |
| private final ReentrantLock mutex = new ReentrantLock(false); |
| private final Condition condition = mutex.newCondition(); |
| |
| public MemoryLimitController(long memoryLimitBytes) { |
| this.memoryLimit = memoryLimitBytes; |
| } |
| |
| public boolean tryReserveMemory(long size) { |
| while (true) { |
| long current = currentUsage.get(); |
| long newUsage = current + size; |
| |
| // We allow one request to go over the limit, to make the notification |
| // path simpler and more efficient |
| if (current > memoryLimit && memoryLimit > 0) { |
| return false; |
| } |
| |
| if (currentUsage.compareAndSet(current, newUsage)) { |
| return true; |
| } |
| } |
| } |
| |
| public void reserveMemory(long size) throws InterruptedException { |
| if (!tryReserveMemory(size)) { |
| mutex.lock(); |
| |
| try { |
| while (!tryReserveMemory(size)) { |
| condition.await(); |
| } |
| } finally { |
| mutex.unlock(); |
| } |
| } |
| } |
| |
| public void releaseMemory(long size) { |
| long newUsage = currentUsage.addAndGet(-size); |
| if (newUsage + size > memoryLimit && newUsage <= memoryLimit) { |
| // We just crossed the limit. Now we have more space |
| mutex.lock(); |
| try { |
| condition.signalAll(); |
| } finally { |
| mutex.unlock(); |
| } |
| } |
| } |
| |
| public long currentUsage() { |
| return currentUsage.get(); |
| } |
| } |