Gargi-jais11 commented on code in PR #9166: URL: https://github.com/apache/ozone/pull/9166#discussion_r2471737352
########## hadoop-hdds/client/src/main/java/org/apache/hadoop/ozone/client/io/BoundedElasticByteBufferPool.java: ########## @@ -0,0 +1,148 @@ +/* + * 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.ozone.client.io; + +import com.google.common.annotations.VisibleForTesting; +import com.google.common.collect.ComparisonChain; +import java.nio.ByteBuffer; +import java.util.Map; +import java.util.TreeMap; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.commons.lang3.builder.HashCodeBuilder; +import org.apache.hadoop.io.ByteBufferPool; + +/** + * A bounded version of ElasticByteBufferPool that limits the total size + * of buffers that can be cached in the pool. This prevents unbounded memory + * growth in long-lived rpc clients like S3 Gateway. + * + * When the pool reaches its maximum size, newly returned buffers are not + * added back to the pool and will be garbage collected instead. + */ +public class BoundedElasticByteBufferPool implements ByteBufferPool { + private final TreeMap<Key, ByteBuffer> buffers = new TreeMap<>(); + private final TreeMap<Key, ByteBuffer> directBuffers = new TreeMap<>(); + private final long maxPoolSize; + private final AtomicLong currentPoolSize = new AtomicLong(0); + + /** + * A logical timestamp counter used for creating unique Keys in the TreeMap. + * This is used as the insertionTime for the Key instead of System.nanoTime() + * to guarantee uniqueness and avoid a potential spin-wait in putBuffer + * if two buffers of the same capacity are added at the same nanosecond. + */ + private long logicalTimestamp = 0; + + public BoundedElasticByteBufferPool(long maxPoolSize) { + super(); + this.maxPoolSize = maxPoolSize; + } + + private TreeMap<Key, ByteBuffer> getBufferTree(boolean direct) { + return direct ? this.directBuffers : this.buffers; + } + + @Override + public synchronized ByteBuffer getBuffer(boolean direct, int length) { + TreeMap<Key, ByteBuffer> tree = this.getBufferTree(direct); + Map.Entry<Key, ByteBuffer> entry = tree.ceilingEntry(new Key(length, 0L)); + if (entry == null) { + // Pool is empty or has no suitable buffer. Allocate a new one. + return direct ? ByteBuffer.allocateDirect(length) : ByteBuffer.allocate(length); + } + tree.remove(entry.getKey()); + ByteBuffer buffer = entry.getValue(); + + // Decrement the size because we are taking a buffer OUT of the pool. + currentPoolSize.addAndGet(-buffer.capacity()); + buffer.clear(); + return buffer; + } Review Comment: The `BufferPool` is linked to is a blocking, fixed-size pool. Its purpose is to strictly limit the total number of buffers ever created (e.g., "this system will only ever use 100 buffers, total"). If you ask for buffer 101, `getBuffer` will wait until one is returned. Our `BoundedElasticByteBufferPool` is a non-blocking, caching pool. Its purpose is to fix a memory leak from the original ElasticByteBufferPool (which grew forever) while preserving its "elastic" (non-blocking) nature. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
