| /** |
| * 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.storm.windowing.persistence; |
| |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.Objects; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.ConcurrentSkipListMap; |
| import java.util.concurrent.locks.ReentrantLock; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * A simple implementation that evicts the largest un-pinned entry from the cache. This works well for caching window partitions since the |
| * access pattern is mostly sequential scans. |
| */ |
| public class SimpleWindowPartitionCache<K, V> implements WindowPartitionCache<K, V> { |
| private static final Logger LOG = LoggerFactory.getLogger(SimpleWindowPartitionCache.class); |
| |
| private final ConcurrentSkipListMap<K, V> map = new ConcurrentSkipListMap<>(); |
| private final Map<K, Long> pinned = new HashMap<>(); |
| private final long maximumSize; |
| private final RemovalListener<K, V> removalListener; |
| private final CacheLoader<K, V> cacheLoader; |
| private final ReentrantLock lock = new ReentrantLock(true); |
| private int size; |
| |
| private SimpleWindowPartitionCache(long maximumSize, RemovalListener<K, V> removalListener, CacheLoader<K, V> cacheLoader) { |
| if (maximumSize <= 0) { |
| throw new IllegalArgumentException("maximumSize must be greater than 0"); |
| } |
| Objects.requireNonNull(cacheLoader); |
| this.maximumSize = maximumSize; |
| this.removalListener = removalListener; |
| this.cacheLoader = cacheLoader; |
| } |
| |
| public static <K, V> SimpleWindowPartitionCacheBuilder<K, V> newBuilder() { |
| return new SimpleWindowPartitionCacheBuilder<>(); |
| } |
| |
| @Override |
| public V get(K key) { |
| return getOrLoad(key, false); |
| } |
| |
| @Override |
| public V pinAndGet(K key) { |
| return getOrLoad(key, true); |
| } |
| |
| @Override |
| public boolean unpin(K key) { |
| LOG.debug("unpin '{}'", key); |
| boolean res = false; |
| try { |
| lock.lock(); |
| Long val = pinned.computeIfPresent(key, (k, v) -> v - 1); |
| if (val != null) { |
| if (val <= 0) { |
| pinned.remove(key); |
| } |
| res = true; |
| } |
| } finally { |
| lock.unlock(); |
| } |
| LOG.debug("pinned '{}'", pinned); |
| return res; |
| } |
| |
| @Override |
| public ConcurrentMap<K, V> asMap() { |
| return map; |
| } |
| |
| @Override |
| public void invalidate(K key) { |
| try { |
| lock.lock(); |
| if (isPinned(key)) { |
| LOG.debug("Entry '{}' is pinned, skipping invalidation", key); |
| } else { |
| LOG.debug("Invalidating entry '{}'", key); |
| V val = map.remove(key); |
| if (val != null) { |
| --size; |
| pinned.remove(key); |
| if (removalListener != null) { |
| removalListener.onRemoval(key, val, RemovalCause.EXPLICIT); |
| } |
| } |
| } |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| // Get or load from the cache optionally pinning the entry |
| // so that it wont get evicted from the cache |
| private V getOrLoad(K key, boolean shouldPin) { |
| V val; |
| if (shouldPin) { |
| try { |
| lock.lock(); |
| val = load(key); |
| pin(key); |
| } finally { |
| lock.unlock(); |
| } |
| } else { |
| val = map.get(key); |
| if (val == null) { |
| try { |
| lock.lock(); |
| val = load(key); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| } |
| |
| return val; |
| } |
| |
| private V load(K key) { |
| V val = map.get(key); |
| if (val == null) { |
| val = cacheLoader.load(key); |
| if (val == null) { |
| throw new NullPointerException("Null value for key " + key); |
| } |
| ensureCapacity(); |
| map.put(key, val); |
| ++size; |
| } |
| return val; |
| } |
| |
| private void ensureCapacity() { |
| if (size >= maximumSize) { |
| Iterator<Map.Entry<K, V>> it = map.descendingMap().entrySet().iterator(); |
| while (it.hasNext()) { |
| Map.Entry<K, V> next = it.next(); |
| if (!isPinned(next.getKey())) { |
| it.remove(); |
| if (removalListener != null) { |
| removalListener.onRemoval(next.getKey(), next.getValue(), RemovalCause.REPLACED); |
| } |
| --size; |
| break; |
| } |
| } |
| } |
| } |
| |
| private void pin(K key) { |
| LOG.debug("pin '{}'", key); |
| pinned.compute(key, (k, v) -> v == null ? 1L : v + 1); |
| LOG.debug("pinned '{}'", pinned); |
| } |
| |
| private boolean isPinned(K key) { |
| return pinned.getOrDefault(key, 0L) > 0; |
| } |
| |
| public static class SimpleWindowPartitionCacheBuilder<K, V> implements WindowPartitionCache.Builder<K, V> { |
| private long maximumSize; |
| private RemovalListener<K, V> removalListener; |
| |
| public SimpleWindowPartitionCacheBuilder<K, V> maximumSize(long size) { |
| maximumSize = size; |
| return this; |
| } |
| |
| public SimpleWindowPartitionCacheBuilder<K, V> removalListener(RemovalListener<K, V> listener) { |
| removalListener = listener; |
| return this; |
| } |
| |
| public SimpleWindowPartitionCache<K, V> build(CacheLoader<K, V> loader) { |
| return new SimpleWindowPartitionCache<>(maximumSize, removalListener, loader); |
| } |
| } |
| } |