ben-manes commented on a change in pull request #16130: URL: https://github.com/apache/beam/pull/16130#discussion_r766202605
########## File path: sdks/java/harness/src/main/java/org/apache/beam/fn/harness/Caches.java ########## @@ -0,0 +1,285 @@ +/* + * 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.beam.fn.harness; + +import java.util.Arrays; +import java.util.Collections; +import java.util.Objects; +import java.util.Set; +import java.util.function.Function; +import org.apache.beam.sdk.options.PipelineOptions; +import org.apache.beam.sdk.options.SdkHarnessOptions; +import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting; +import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Sets; +import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.util.concurrent.MoreExecutors; +import org.cache2k.Cache2kBuilder; +import org.cache2k.operation.Weigher; +import org.github.jamm.MemoryMeter; + +/** Utility methods used to instantiate and operate over cache instances. */ +@SuppressWarnings("nullness") +public final class Caches { + + /** A cache that never stores any values. */ + public static <K, V> Cache<K, V> noop() { + return new SubCacheable<K, V>() { + @Override + public V peek(K key) { + return null; + } + + @Override + public V computeIfAbsent(K key, Function<K, V> loadingFunction) { + return loadingFunction.apply(key); + } + + @Override + public void put(K key, V value) {} + + @Override + public void clear() {} + + @Override + public void remove(K key) {} + + @Override + public Set<K> keys() { + return Collections.emptySet(); + } + }; + } + + /** + * Uses the specified {@link PipelineOptions} to configure and return a cache instance based upon + * parameters within {@link SdkHarnessOptions}. + */ + public static <K, V> Cache<K, V> fromOptions(PipelineOptions options) { + // We specifically use cache2k since it allows for recursive computeIfAbsent calls + // preventing deadlock from occurring when a loading function mutates the underlying cache + org.cache2k.Cache<Object, Object> cache = + Cache2kBuilder.forUnknownTypes() + .maximumWeight( + options.as(SdkHarnessOptions.class).getMaxCacheMemoryUsageMb() * 1024L * 1024L) + .weigher( + new Weigher<Object, Object>() { + private final MemoryMeter memoryMeter = MemoryMeter.builder().build(); + + @Override + public int weigh(Object key, Object value) { + long size = memoryMeter.measureDeep(key) + memoryMeter.measureDeep(value); + return size > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) size; + } + }) + .storeByReference(true) + .executor(MoreExecutors.directExecutor()) + .build(); + + return (Cache<K, V>) forCache(cache); + } + + /** + * Returns a view of a cache that operates on keys with a specified key prefix. + * + * <p>All lookups, insertions, and removals into the parent {@link Cache} will be prefixed by the + * specified prefixes. + * + * <p>Operations which operate over the entire caches contents such as {@link Cache#clear} only + * operate over keys with the specified prefixes. + */ + public static <K, V> Cache<K, V> subCache( + Cache<?, ?> cache, Object keyPrefix, Object... additionalKeyPrefix) { + if (cache instanceof SubCache) { + return new SubCache<>( + ((SubCache<?, ?>) cache).cache, + ((SubCache<?, ?>) cache).keyPrefix.subKey(keyPrefix, additionalKeyPrefix)); + } else if (cache instanceof SubCacheable) { + return new SubCache<>((SubCacheable<?, ?>) cache, CompositeKey.ROOT.subKey(keyPrefix)); + } + throw new UnsupportedOperationException("An unsupported type of cache was passed."); + } + + /** A cache that never evicts any values. */ + public static <K, V> Cache<K, V> eternal() { + // We specifically use cache2k since it allows for recursive computeIfAbsent calls Review comment: In this case I would recommend Guava `get(key, callable)` because does support X -> Y-> Z, has been used at scale for known robustness, and it's an unofficially supported behavior. Recursive loads was tested for, fixed, discussed, and relied upon internally (e.g. by Gerrit). Otherwise an explicit lock object like the future example is ideal. I don't think you should rely on accidental behavior as your current implementation does. Note that Guava's `get(key, callable)` is very robust for this, but it's `asMap().compute` methods were added semi-recently and likely not. I'm not familiar enough but would be happy to discuss over email or a video conf if I can be of help. You might be able to use a weak value for your view caches so that they discard when the entry is evicted by the primary cache. Other times I've used index caches that maintain a secondaryKey => primaryKey mapping for a primaryKey => value cache, so it takes two lookups. The callbacks and/or reference caching can help a lot in orchestrating these complex cases. -- This is an automated message from the Apache Git Service. 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