/* * 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.concurrent; import java.lang.ref.PhantomReference; import java.lang.ref.ReferenceQueue; import java.util.*; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentLinkedQueue; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; import com.google.common.collect.ImmutableMap; import com.google.common.collect.Iterators; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.cassandra.concurrent.NamedThreadFactory; /** * An object that needs ref counting does the two following: * - defines a Tidy object that will cleanup once it's gone, * (this must retain no references to the object we're tracking (only its resources and how to clean up)) * Then, one of two options: * 1) Construct a Ref directly pointing to it, and always use this Ref; or * 2) * - implements RefCounted * - encapsulates a Ref, we'll call selfRef, to which it proxies all calls to RefCounted behaviours * - users must ensure no references to the selfRef leak, or are retained outside of a method scope. * (to ensure the selfRef is collected with the object, so that leaks may be detected and corrected) */ public interface RefCounted<T> { /** * @return the a new Ref() to the managed object, incrementing its refcount, or null if it is already released */ public Ref<T> tryRef(); public Ref<T> ref(); public static interface Tidy { void tidy() throws Exception; String name(); } }