com.couchbase.client.core.util.PreventsGarbageCollection Maven / Gradle / Ivy
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/*
* Copyright 2023 Couchbase, Inc.
*
* Licensed 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
*
* https://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 com.couchbase.client.core.util;
import com.couchbase.client.core.annotation.Stability;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Indicates that at least one purpose of the annotated field
* is to prevent the value from being garbage collected.
*
* This annotation is strictly advisory, and has no effect at runtime.
*
* Why do we hold references just to prevent garbage collection?
* One reason is because we want to automatically disconnect an AsyncCluster
* when it becomes unreachable, so the Core doesn't live on as
* a socket-slurping zombie. However, we don't want
* to disconnect the cluster until any Buckets, Scopes, Collections,
* and Managers associated with the cluster also become unreachable.
* To that end, each of those "satellite" objects holds a reference
* back to the cluster, just to prevent the cluster from becoming
* unreachable until all the satellites are also unreachable.
*
* We explored attaching the "auto-disconnect" behavior to the
* Core instead of the cluster, but unfortunately the Core
* never becomes eligible for garbage collection, presumably
* because it's referenced by one or more schedulers.
*/
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.FIELD)
@Stability.Internal
public @interface PreventsGarbageCollection {
}