adoroszlai commented on code in PR #5853: URL: https://github.com/apache/ozone/pull/5853#discussion_r1435068781
########## hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/resource/package-info.java: ########## @@ -0,0 +1,22 @@ +/** + * 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.hadoop.hdds.resource; + +/** + * Contain utilities for resource management. + */ Review Comment: nit: ```suggestion /** * Contains utilities for resource management. */ package org.apache.hadoop.hdds.resource; ``` ########## hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/resource/package-info.java: ########## @@ -0,0 +1,22 @@ +/** Review Comment: nit: ```suggestion /* ``` ########## hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/resource/LeakDetector.java: ########## @@ -0,0 +1,102 @@ +/* + * 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.hadoop.hdds.resource; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.lang.ref.ReferenceQueue; +import java.util.Collections; +import java.util.Set; +import java.util.concurrent.ConcurrentHashMap; + +/** + * Simple general resource leak detector using {@link ReferenceQueue} and {@link java.lang.ref.WeakReference} to + * observe resource object life-cycle and assert proper resource closure before they are GCed. + * + * <p> + * Example usage: + * + * <pre> {@code + * class MyResource implements AutoClosable { + * static final LeakDetector LEAK_DETECTOR = new LeakDetector("MyResource"); + * + * private final LeakTracker leakTracker = LEAK_DETECTOR.track(this, () -> { + * // report leaks, don't refer to the original object (MyResource) here. + * System.out.println("MyResource is not closed before being discarded."); + * }); + * + * @Override + * public void close() { + * // proper resources cleanup... + * // inform tracker that this object is closed properly. + * leakTracker.close(); + * } + * } + * + * }</pre> + */ +public class LeakDetector implements Runnable { + public static final Logger LOG = LoggerFactory.getLogger(LeakDetector.class); + private final ReferenceQueue<Object> queue = new ReferenceQueue<>(); + private final Set<LeakTracker> allLeaks = Collections.newSetFromMap(new ConcurrentHashMap<>()); + private final String name; + + public LeakDetector(String name) { + this.name = name; + start(); + } + + private void start() { + Thread t = new Thread(this); + t.setName(LeakDetector.class.getSimpleName() + "-" + name); + t.setDaemon(true); + LOG.info("Starting leak detector thread {}.", name); + t.start(); + } + + @Override + public void run() { + while (true) { + try { + LeakTracker tracker = (LeakTracker) queue.remove(); + // Original resource already been GCed, if tracker is not closed yet, + // report a leak. + if (allLeaks.remove(tracker)) { + tracker.reportLeak(); + } + } catch (InterruptedException e) { + LOG.warn("Thread interrupted, exiting.", e); + break; + } + } + + LOG.warn("Existing leak detector {}.", name); Review Comment: typo? ```suggestion LOG.warn("Exiting leak detector {}.", name); ``` ########## hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/resource/LeakTracker.java: ########## @@ -0,0 +1,50 @@ +/* + * 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.hadoop.hdds.resource; + +import java.lang.ref.ReferenceQueue; +import java.lang.ref.WeakReference; +import java.util.Set; + +/** + * A token to track resource closure. + * + * @see LeakDetector + */ +public class LeakTracker extends WeakReference<Object> { + private final Set<LeakTracker> allLeaks; + private final Runnable leakReporter; + LeakTracker(Object referent, ReferenceQueue<? super Object> referenceQueue, Review Comment: Can simplify a bit: ```suggestion LeakTracker(Object referent, ReferenceQueue<Object> referenceQueue, ``` -- This is an automated message from the Apache Git Service. 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