qiaojialin commented on a change in pull request #802: Cached chunk URL: https://github.com/apache/incubator-iotdb/pull/802#discussion_r379263215
########## File path: server/src/main/java/org/apache/iotdb/db/engine/cache/ChunkCache.java ########## @@ -0,0 +1,153 @@ +/* + * 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.iotdb.db.engine.cache; + +import org.apache.iotdb.db.conf.IoTDBConfig; +import org.apache.iotdb.db.conf.IoTDBDescriptor; +import org.apache.iotdb.tsfile.file.metadata.ChunkMetaData; +import org.apache.iotdb.tsfile.read.TsFileSequenceReader; +import org.apache.iotdb.tsfile.read.common.Chunk; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.concurrent.atomic.AtomicLong; +import java.util.concurrent.locks.Lock; +import java.util.concurrent.locks.ReadWriteLock; +import java.util.concurrent.locks.ReentrantReadWriteLock; + +/** + * This class is used to cache <code>Chunk</code> of <code>ChunkMetaData</code> in IoTDB. The caching + * strategy is LRU. + */ +public class ChunkCache { + + private static final Logger logger = LoggerFactory.getLogger(ChunkCache.class); + private static final IoTDBConfig config = IoTDBDescriptor.getInstance().getConfig(); + private static final long MEMORY_THRESHOLD_IN_CHUNK_CACHE = config.getAllocateMemoryForChunkCache(); + private static boolean cacheEnable = config.isMetaDataCacheEnable(); + + private final LRULinkedHashMap<ChunkMetaData, Chunk> lruCache; + + private AtomicLong cacheHitNum = new AtomicLong(); + private AtomicLong cacheRequestNum = new AtomicLong(); + + private final ReadWriteLock lock = new ReentrantReadWriteLock(); + private final Lock readLock = lock.readLock(); + private final Lock writeLock = lock.writeLock(); + + + private ChunkCache() { + lruCache = new LRULinkedHashMap<ChunkMetaData, Chunk>(MEMORY_THRESHOLD_IN_CHUNK_CACHE, true) { + @Override + protected long calEntrySize(ChunkMetaData key, Chunk value) { + return RamUsageEstimator.sizeOf(value) + RamUsageEstimator.sizeOf(value); + } + }; + } + + public static ChunkCache getInstance() { + return ChunkCacheHolder.INSTANCE; + } + + public Chunk get(ChunkMetaData chunkMetaData, TsFileSequenceReader reader) throws IOException { + if (!cacheEnable) { + Chunk chunk = reader.readMemChunk(chunkMetaData); + return new Chunk(chunk.getHeader(), chunk.getData().duplicate(), chunk.getDeletedAt(), reader.getEndianType()); + } + + cacheRequestNum.incrementAndGet(); + + try { + readLock.lock(); + if (lruCache.containsKey(chunkMetaData)) { + cacheHitNum.incrementAndGet(); + printCacheLog(true); + Chunk chunk = lruCache.get(chunkMetaData); + return new Chunk(chunk.getHeader(), chunk.getData().duplicate(), chunk.getDeletedAt(), reader.getEndianType()); + } + } finally { + readLock.unlock(); + } + + writeLock.lock(); + if (lruCache.containsKey(chunkMetaData)) { + writeLock.unlock(); + readLock.lock(); + cacheHitNum.incrementAndGet(); + printCacheLog(true); + Chunk chunk = lruCache.get(chunkMetaData); + readLock.unlock(); + return new Chunk(chunk.getHeader(), chunk.getData().duplicate(), chunk.getDeletedAt(), reader.getEndianType()); + } + printCacheLog(false); + Chunk chunk = reader.readMemChunk(chunkMetaData); + lruCache.put(chunkMetaData, chunk); + writeLock.unlock(); + return new Chunk(chunk.getHeader(), chunk.getData().duplicate(), chunk.getDeletedAt(), reader.getEndianType()); Review comment: ```suggestion return chunk; ``` ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
