| /* |
| * 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; |
| |
| |
| import com.google.common.base.Preconditions; |
| import org.apache.druid.common.config.NullHandling; |
| import org.apache.druid.java.util.common.logger.Logger; |
| import org.apache.druid.query.lookup.LookupExtractor; |
| import org.apache.druid.server.lookup.cache.loading.LoadingCache; |
| |
| import javax.annotation.Nullable; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.ExecutionException; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| |
| /** |
| * Loading lookup will load the key\value pair upon request on the key it self, the general algorithm is load key if absent. |
| * Once the key/value pair is loaded eviction will occur according to the cache eviction policy. |
| * This module comes with two loading cache implementations, the first {@link org.apache.druid.server.lookup.cache.loading.OnHeapLoadingCache}is onheap backed by a Guava cache implementation, the second {@link org.apache.druid.server.lookup.cache.loading.OffHeapLoadingCache}is MapDB offheap implementation. |
| * Both implementations offer various eviction strategies. |
| */ |
| public class LoadingLookup extends LookupExtractor |
| { |
| private static final Logger LOGGER = new Logger(LoadingLookup.class); |
| |
| private final DataFetcher<String, String> dataFetcher; |
| private final LoadingCache<String, String> loadingCache; |
| private final LoadingCache<String, List<String>> reverseLoadingCache; |
| private final AtomicBoolean isOpen; |
| private final String id = Integer.toHexString(System.identityHashCode(this)); |
| |
| public LoadingLookup( |
| DataFetcher dataFetcher, |
| LoadingCache<String, String> loadingCache, |
| LoadingCache<String, List<String>> reverseLoadingCache |
| ) |
| { |
| this.dataFetcher = Preconditions.checkNotNull(dataFetcher, "lookup must have a DataFetcher"); |
| this.loadingCache = Preconditions.checkNotNull(loadingCache, "loading lookup need a cache"); |
| this.reverseLoadingCache = Preconditions.checkNotNull(reverseLoadingCache, "loading lookup need reverse cache"); |
| this.isOpen = new AtomicBoolean(true); |
| } |
| |
| |
| @Override |
| public String apply(@Nullable final String key) |
| { |
| String keyEquivalent = NullHandling.nullToEmptyIfNeeded(key); |
| if (keyEquivalent == null) { |
| // valueEquivalent is null only for SQL Compatible Null Behavior |
| // otherwise null will be replaced with empty string in nullToEmptyIfNeeded above. |
| return null; |
| } |
| |
| final String presentVal; |
| try { |
| presentVal = loadingCache.get(keyEquivalent, new ApplyCallable(keyEquivalent)); |
| return NullHandling.emptyToNullIfNeeded(presentVal); |
| } |
| catch (ExecutionException e) { |
| LOGGER.debug("value not found for key [%s]", key); |
| return null; |
| } |
| } |
| |
| @Override |
| public List<String> unapply(@Nullable final String value) |
| { |
| String valueEquivalent = NullHandling.nullToEmptyIfNeeded(value); |
| if (valueEquivalent == null) { |
| // valueEquivalent is null only for SQL Compatible Null Behavior |
| // otherwise null will be replaced with empty string in nullToEmptyIfNeeded above. |
| // null value maps to empty list when SQL Compatible |
| return Collections.emptyList(); |
| } |
| final List<String> retList; |
| try { |
| retList = reverseLoadingCache.get(valueEquivalent, new UnapplyCallable(valueEquivalent)); |
| return retList; |
| } |
| catch (ExecutionException e) { |
| LOGGER.debug("list of keys not found for value [%s]", value); |
| return Collections.emptyList(); |
| } |
| } |
| |
| @Override |
| public boolean canIterate() |
| { |
| return false; |
| } |
| |
| @Override |
| public Iterable<Map.Entry<String, String>> iterable() |
| { |
| throw new UnsupportedOperationException("Cannot iterate"); |
| } |
| |
| @Override |
| public byte[] getCacheKey() |
| { |
| return LookupExtractionModule.getRandomCacheKey(); |
| } |
| |
| private class ApplyCallable implements Callable<String> |
| { |
| private final String key; |
| |
| public ApplyCallable(String key) |
| { |
| this.key = key; |
| } |
| |
| @Override |
| public String call() |
| { |
| // When SQL compatible null handling is disabled, |
| // avoid returning null and return an empty string to cache it. |
| return NullHandling.nullToEmptyIfNeeded(dataFetcher.fetch(key)); |
| } |
| } |
| |
| public synchronized void close() |
| { |
| if (isOpen.getAndSet(false)) { |
| LOGGER.info("Closing loading cache [%s]", id); |
| loadingCache.close(); |
| reverseLoadingCache.close(); |
| } else { |
| LOGGER.info("Closing already closed lookup"); |
| } |
| } |
| |
| public boolean isOpen() |
| { |
| return isOpen.get(); |
| } |
| |
| private class UnapplyCallable implements Callable<List<String>> |
| { |
| private final String value; |
| |
| public UnapplyCallable(String value) |
| { |
| this.value = value; |
| } |
| |
| @Override |
| public List<String> call() |
| { |
| return dataFetcher.reverseFetchKeys(value); |
| } |
| } |
| |
| @Override |
| public String toString() |
| { |
| return "LoadingLookup{" + |
| "dataFetcher=" + dataFetcher + |
| ", id='" + id + '\'' + |
| '}'; |
| } |
| } |