poorbarcode commented on code in PR #24457: URL: https://github.com/apache/pulsar/pull/24457#discussion_r2166661706
########## pulsar-common/src/main/java/org/apache/pulsar/common/naming/NameCache.java: ########## @@ -0,0 +1,156 @@ +/* + * 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.pulsar.common.naming; + +import com.google.common.collect.Interner; +import com.google.common.collect.Interners; +import java.lang.ref.ReferenceQueue; +import java.lang.ref.SoftReference; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicLong; +import org.apache.pulsar.common.util.StringInterner; + +/** + * A cache for TopicName and NamespaceName instances that allows deduplication and efficient memory usage. + * It uses soft references to allow garbage collection of unused instances under heavy memory pressure. + * This cache uses ConcurrentHashMap for lookups for performance over Guava Cache and Caffeine Cache + * since there was a concern in https://github.com/apache/pulsar/pull/23052 about high CPU usage for TopicName lookups. + */ +abstract class NameCache<V> { + // Cache instances using ConcurrentHashMap and SoftReference to allow garbage collection to clear unreferenced + // entries when heap memory is running low. + private final ConcurrentMap<String, SoftReferenceValue> cache = new ConcurrentHashMap<>(); + // Reference queue to hold cleared soft references, which will be used to remove entries from the cache. + private final ReferenceQueue<? super V> referenceQueue = new ReferenceQueue<>(); Review Comment: This is indeed a reverse optimization - **Background**: When memory is very tight, the objects referenced by SoftReference will be cleared. - TopicName is a core concept in Pulsar. If the Topic does not exist, the TopicName object will be cleared during Young GC. - On the contrary, if the TopicName is still in memory when memory usage is tight, it indicates that this topic is an active topic. After being cleared, it will be immediately rebuilt, causing an infinite loop and seriously affecting CPU performance -- 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: commits-unsubscr...@pulsar.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
