HonahX commented on code in PR #490: URL: https://github.com/apache/polaris/pull/490#discussion_r1959032129
########## polaris-core/src/main/java/org/apache/polaris/core/persistence/cache/EntityWeigher.java: ########## @@ -0,0 +1,64 @@ +/* + * 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.polaris.core.persistence.cache; + +import com.github.benmanes.caffeine.cache.Weigher; +import org.checkerframework.checker.index.qual.NonNegative; + +/** + * A {@link Weigher} implementation that weighs {@link EntityCacheEntry} objects by the approximate + * size of the entity object. + */ +public class EntityWeigher implements Weigher<Long, EntityCacheEntry> { + + /** The amount of weight that is expected to roughly equate to 1MB of memory usage */ + public static final long WEIGHT_PER_MB = 1024 * 1024; + + /* Represents the approximate size of an entity beyond the properties */ + private static final int APPROXIMATE_ENTITY_OVERHEAD = 1000; + + /** Singleton instance */ + private static final EntityWeigher instance = new EntityWeigher(); + + private EntityWeigher() {} + + /** Gets the singleton {@link EntityWeigher} */ + public static EntityWeigher getInstance() { + return instance; + } + + /** + * Computes the weight of a given entity + * + * @param key The entity's key; not used + * @param value The entity to be cached + * @return The weight of the entity + */ + @Override + public @NonNegative int weigh(Long key, EntityCacheEntry value) { + return APPROXIMATE_ENTITY_OVERHEAD + + value.getEntity().getProperties().length() + + value.getEntity().getInternalProperties().length(); Review Comment: Just to confirm my understanding: if the main concern is the difference between a string's length and its actual memory usage, could we address this by multiplying String.length() by an estimated factor, such as 2 or 3? And I agree that, regardless of the exact multiplier, this would help us "bound" the overall size of the cache ########## polaris-core/src/main/java/org/apache/polaris/core/persistence/cache/EntityCache.java: ########## @@ -71,12 +71,13 @@ public EntityCache(@NotNull PolarisRemoteCache polarisRemoteCache) { }; // use a Caffeine cache to purge entries when those have not been used for a long time. - // Assuming 1KB per entry, 100K entries is about 100MB. this.byId = Caffeine.newBuilder() - .maximumSize(100_000) // Set maximum size to 100,000 elements + .maximumWeight(100 * EntityWeigher.WEIGHT_PER_MB) // Goal is ~100MB Review Comment: I think making the maximum configurable is a good thing but may be out-of-scope of this PR. Probably we can do that as a follow-up? -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
