smiklosovic commented on code in PR #2577: URL: https://github.com/apache/cassandra/pull/2577#discussion_r1300335770
########## src/java/org/apache/cassandra/utils/ReflectionUtils.java: ########## @@ -0,0 +1,94 @@ +/* + * 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.cassandra.utils; + +import java.lang.reflect.Field; +import java.lang.reflect.Method; +import java.util.Iterator; +import java.util.Map; +import java.util.function.Predicate; + +public class ReflectionUtils { + public static Field getField(Class<?> clazz, String fieldName) throws NoSuchFieldException + { + // below code works before Java 12 + try + { + return clazz.getDeclaredField(fieldName); + } + catch (NoSuchFieldException e) + { + // this is mitigation for JDK 17 (https://bugs.openjdk.org/browse/JDK-8210522) + try + { + Method getDeclaredFields0 = Class.class.getDeclaredMethod("getDeclaredFields0", boolean.class); + getDeclaredFields0.setAccessible(true); + Field[] fields = (Field[]) getDeclaredFields0.invoke(clazz, false); + for (Field field : fields) + { + if (fieldName.equals(field.getName())) + { + return field; + } + } + } + catch (ReflectiveOperationException ex) + { + e.addSuppressed(ex); + } + throw e; + } + } + + /** + * Used by the in-jvm dtest framework to remove entries from private map fields that otherwise would prevent + * collection of classloaders (which causes metaspace OOMs) or otherwise interfere with instance restart. + * @param clazz The class which has the map field to clear + * @param instance an instance of the class to clear (pass null for a static member) + * @param mapName the name of the map field to clear + * @param shouldRemove a predicate which determines if the entry in question should be removed + * @param <K> The type of the map key + * @param <V> The type of the map value + */ + public static <K, V> void clearMapField(Class<?> clazz, Object instance, String mapName, Predicate<Map.Entry<K, V>> shouldRemove) { + try + { + Field mapField = getField(clazz, mapName); + mapField.setAccessible(true); + // noinspection unchecked + Map<K, V> map = (Map<K, V>) mapField.get(instance); + // Because multiple instances can be shutting down at once, + // synchronize on the map to avoid ConcurrentModificationException + synchronized (map) + { + // This could be done with a simple `map.entrySet.removeIf()` call + // but for debugging purposes it is much easier to keep it like this. + Iterator<Map.Entry<K,V>> it = map.entrySet().iterator(); + while (it.hasNext()) { Review Comment: here too, `it.remove()` does not need to be put in `{ }` as it is the only statement in that `if`. -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
