org.apache.druid.server.lookup.cache.polling.OffHeapPollingCache.java Source code

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Here is the source code for org.apache.druid.server.lookup.cache.polling.OffHeapPollingCache.java

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/*
 * 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.druid.server.lookup.cache.polling;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import org.apache.druid.java.util.common.StringUtils;
import org.mapdb.DB;
import org.mapdb.DBMaker;
import org.mapdb.HTreeMap;

import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicBoolean;

public class OffHeapPollingCache<K, V> implements PollingCache<K, V> {
    private static final DB DB = DBMaker.newMemoryDirectDB().transactionDisable().closeOnJvmShutdown().make();

    private final HTreeMap<K, V> mapCache;
    private final HTreeMap<V, List<K>> reverseCache;
    private final AtomicBoolean started = new AtomicBoolean(false);
    private final String cacheName;
    private final String reverseCacheName;

    public OffHeapPollingCache(final Iterable<Map.Entry<K, V>> entries) {
        synchronized (started) {
            this.cacheName = StringUtils.format("cache-%s", UUID.randomUUID());
            this.reverseCacheName = StringUtils.format("reverseCache-%s", UUID.randomUUID());
            mapCache = DB.createHashMap(cacheName).make();
            reverseCache = DB.createHashMap(reverseCacheName).make();
            ImmutableSet.Builder<V> setOfValuesBuilder = ImmutableSet.builder();
            for (Map.Entry<K, V> entry : entries) {
                mapCache.put(entry.getKey(), entry.getValue());
                setOfValuesBuilder.add(entry.getValue());
            }

            final Set<V> setOfValues = setOfValuesBuilder.build();
            reverseCache.putAll(Maps.asMap(setOfValues, new Function<V, List<K>>() {
                @Override
                public List<K> apply(final V input) {
                    return Lists.newArrayList(Maps.filterKeys(mapCache, new Predicate<K>() {
                        @Override
                        public boolean apply(K key) {
                            V retVal = mapCache.get(key);
                            if (retVal == null) {
                                return false;
                            }
                            return retVal.equals(input);
                        }
                    }).keySet());
                }
            }));
            started.getAndSet(true);
        }
    }

    @Override
    public V get(K key) {
        return mapCache.get(key);
    }

    @Override
    public List<K> getKeys(V value) {
        final List<K> listOfKey = reverseCache.get(value);
        if (listOfKey == null) {
            return Collections.emptyList();
        }
        return listOfKey;
    }

    @Override
    public void close() {
        synchronized (started) {
            if (started.getAndSet(false)) {
                DB.delete(cacheName);
                DB.delete(reverseCacheName);
            }
        }
    }

    public static class OffHeapPollingCacheProvider<K, V> implements PollingCacheFactory<K, V> {
        @Override
        public PollingCache<K, V> makeOf(Iterable<Map.Entry<K, V>> entries) {
            return new OffHeapPollingCache<>(entries);
        }
    }
}