vy commented on code in PR #3474: URL: https://github.com/apache/logging-log4j2/pull/3474#discussion_r1976659691
########## log4j-core-test/src/main/java/org/apache/logging/log4j/core/test/util/InternalLoggerRegistryGCTest.java: ########## @@ -0,0 +1,127 @@ +/* + * 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.logging.log4j.core.test.util; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertFalse; +import static org.junit.jupiter.api.Assertions.assertNotNull; +import static org.junit.jupiter.api.Assertions.assertNull; +import static org.junit.jupiter.api.Assertions.assertSame; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import java.lang.ref.WeakReference; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import org.apache.logging.log4j.core.Logger; +import org.apache.logging.log4j.core.LoggerContext; +import org.apache.logging.log4j.core.util.internal.InternalLoggerRegistry; +import org.apache.logging.log4j.message.MessageFactory; +import org.apache.logging.log4j.message.SimpleMessageFactory; +import org.junit.jupiter.api.BeforeEach; +import org.junit.jupiter.api.Test; + +class InternalLoggerRegistryTest { + private InternalLoggerRegistry registry; + private MessageFactory messageFactory; + + @BeforeEach + void setUp() { + registry = new InternalLoggerRegistry(); + messageFactory = new SimpleMessageFactory(); + } + + @Test + void testGetLoggerReturnsNullForNonExistentLogger() { + assertNull(registry.getLogger("nonExistent", messageFactory)); + } + + @Test + void testComputeIfAbsentCreatesLogger() { + Logger logger = + registry.computeIfAbsent("testLogger", messageFactory, (name, factory) -> LoggerContext.getContext() + .getLogger(name, factory)); + assertNotNull(logger); + assertEquals("testLogger", logger.getName()); + } + + @Test + void testGetLoggerRetrievesExistingLogger() { + Logger logger = + registry.computeIfAbsent("testLogger", messageFactory, (name, factory) -> LoggerContext.getContext() + .getLogger(name, factory)); + assertSame(logger, registry.getLogger("testLogger", messageFactory)); + } + + @Test + void testHasLoggerReturnsCorrectStatus() { + assertFalse(registry.hasLogger("testLogger", messageFactory)); + registry.computeIfAbsent("testLogger", messageFactory, (name, factory) -> LoggerContext.getContext() + .getLogger(name, factory)); + assertTrue(registry.hasLogger("testLogger", messageFactory)); + } + + @Test + void testExpungeStaleEntriesRemovesGarbageCollectedLoggers() throws InterruptedException { + Logger logger = + registry.computeIfAbsent("testLogger", messageFactory, (name, factory) -> LoggerContext.getContext() + .getLogger(name, factory)); + + WeakReference<Logger> weakRef = new WeakReference<>(logger); + logger = null; // Dereference to allow GC + + // Retry loop to give GC time to collect + for (int i = 0; i < 10; i++) { + System.gc(); + Thread.sleep(100); + if (weakRef.get() == null) { + break; + } + } + + // Access the registry to potentially trigger cleanup + registry.computeIfAbsent("tempLogger", messageFactory, (name, factory) -> LoggerContext.getContext() + .getLogger(name, factory)); + + assertNull(weakRef.get(), "Logger should have been garbage collected"); + assertNull( + registry.getLogger("testLogger", messageFactory), "Stale logger should be removed from the registry"); Review Comment: Can we instead replace this as follows, please? 1. Use an ephemeral `LoggerContext` (as I described in another comment) 2. Create 1000 `Logger`s (should be many enough to create GC pressure) 3. Log using all `Logger`s (so we imitate a real-world setup where `Logger`s are used at some point) 4. Use `Awaitility.waitAtMost(...).until(...)` to verify that after a `System.gc()`, `InternalLoggerRegistry::loggerRefByNameByMessageFactory` is emptied You can access to `InternalLoggerRegistry::loggerRefByNameByMessageFactory` using reflection. That is, first extract the `LoggerContext::loggerRegistry` field, and then the `InternalLoggerRegistry::loggerRefByNameByMessageFactory` field. ########## log4j-core/src/main/java/org/apache/logging/log4j/core/util/internal/InternalLoggerRegistry.java: ########## @@ -53,13 +57,48 @@ public final class InternalLoggerRegistry { new WeakHashMap<>(); private final ReadWriteLock lock = new ReentrantReadWriteLock(); - private final Lock readLock = lock.readLock(); - private final Lock writeLock = lock.writeLock(); + // ReferenceQueue to track stale WeakReferences + private final ReferenceQueue<Logger> staleLoggerRefs = new ReferenceQueue<>(); + public InternalLoggerRegistry() {} + /** + * Expunges stale logger references from the registry. + */ + private void expungeStaleEntries() { + Reference<? extends Logger> loggerRef; + while ((loggerRef = staleLoggerRefs.poll()) != null) { + removeLogger(loggerRef); + } + } + + /** + * Removes a logger from the registry. + */ + private void removeLogger(Reference<? extends Logger> loggerRef) { + Logger logger = loggerRef.get(); + if (logger == null) return; // Logger already cleared + + MessageFactory messageFactory = logger.getMessageFactory(); + String name = logger.getName(); + + writeLock.lock(); + try { + Map<String, WeakReference<Logger>> loggerRefByName = loggerRefByNameByMessageFactory.get(messageFactory); + if (loggerRefByName != null) { + loggerRefByName.remove(name); + if (loggerRefByName.isEmpty()) { + loggerRefByNameByMessageFactory.remove(messageFactory); // Cleanup + } + } Review Comment: Assume I move this logic (and only this!) to a method called `unsafeRemoveLogger(Logger)`. Note that this method receives a `Logger`, not a `Reference`. ########## log4j-core/src/main/java/org/apache/logging/log4j/core/util/internal/InternalLoggerRegistry.java: ########## @@ -53,13 +57,48 @@ public final class InternalLoggerRegistry { new WeakHashMap<>(); private final ReadWriteLock lock = new ReentrantReadWriteLock(); - private final Lock readLock = lock.readLock(); - private final Lock writeLock = lock.writeLock(); + // ReferenceQueue to track stale WeakReferences + private final ReferenceQueue<Logger> staleLoggerRefs = new ReferenceQueue<>(); + public InternalLoggerRegistry() {} + /** + * Expunges stale logger references from the registry. + */ + private void expungeStaleEntries() { + Reference<? extends Logger> loggerRef; + while ((loggerRef = staleLoggerRefs.poll()) != null) { + removeLogger(loggerRef); + } Review Comment: Would you mind changing this loop as follows, please? ``` boolean locked = false; Reference<? extends Logger> loggerRef; while ((loggerRef = staleLoggerRefs.poll()) != null) { Logger logger = loggerRef.get(); if (logger != null) { if (!locked) { writeLock.lock(); } unsafeRemoveLogger(logger); } } if (locked) { writeLock.unlock(); } ``` See my other comment regarding the `unsafeRemoveLogger(Logger)` method. ########## log4j-core-test/src/main/java/org/apache/logging/log4j/core/test/util/InternalLoggerRegistryGCTest.java: ########## Review Comment: Can you replace `LoggerContext.getContext()` calls as follows, please? ``` @Test void someTest(TestInfo testInfo) { try (final LoggerContext loggerContext = new LoggerContext(testInfo.getDisplayName)) { // Use `loggerContext` } } ``` That is, don't disrupt the global one, use ephemeral `LC`s instead. -- This is an automated message from the Apache Git Service. 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