com.hazelcast.core.OutOfMemoryHandler Maven / Gradle / Ivy

/*
 * Copyright (c) 2008-2018, Hazelcast, Inc. All Rights Reserved.
 *
 * 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
 *
 * 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 com.hazelcast.core;

import com.hazelcast.instance.OutOfMemoryHandlerHelper;

/**
 * Handler for OutOfMemoryError.
 * 
 * When an OutOfMemoryError is caught by Hazelcast threads,
 * OutOfMemoryHandler is called for ALL HazelcastInstances
 * known by the current JVM (actually ClassLoader).
 * 
 *
 * 
 * Warning:  OutOfMemoryHandler may not be called even if JVM throws
 * OutOfMemoryError
 * because the error may be thrown from an external (user) thread, so
 * Hazelcast may not be informed about OutOfMemoryError.
 * 
 *
 * @see OutOfMemoryError
 * @see Hazelcast#setOutOfMemoryHandler(OutOfMemoryHandler)
 *
 */
public abstract class OutOfMemoryHandler {

    /**
     * When an OutOfMemoryError is caught by Hazelcast threads,
     * this method is called for ALL HazelcastInstances
     * knows by current JVM (actually ClassLoader).
     *
     * 
     * User can shutdown the HazelcastInstance, call System.exit(),
     * just log the error, etc.
     * The default handler tries to close socket connections to other nodes and shutdown the
     * HazelcastInstance.
     * 
     *
     * 
     * Warning:  OutOfMemoryHandler may not be called even if JVM throws
     * OutOfMemoryError
     * because the error may be thrown from an external (user) thread
     * and Hazelcast may not be informed about OutOfMemoryError.
     * 
     *
     * @see OutOfMemoryHandler#tryCloseConnections(HazelcastInstance)
     * @see OutOfMemoryHandler#tryShutdown(HazelcastInstance)
     *
     * @param oome OutOfMemoryError thrown by JVM
     * @param hazelcastInstances All HazelcastInstances known by JVM,
     *                           can include inactive or NULL instances.
     */
    public abstract void onOutOfMemory(OutOfMemoryError oome, HazelcastInstance[] hazelcastInstances);

    /**
     * Decides if the OutOfMemoryError thrown will be handled by this OutOfMemoryHandler or not.
     * If true is return, {@link #onOutOfMemory(OutOfMemoryError, HazelcastInstance[])} will be called
     * to handle error, otherwise OutOfMemoryError will be ignored.
     *
     * @param oome OutOfMemoryError thrown by JVM
     * @return true if OutOfMemoryError will be handled, false otherwise
     */
    public boolean shouldHandle(OutOfMemoryError oome) {
        return true;
    }

    /**
     * Tries to close the server socket and connections to other HazelcastInstances.
     *
     * @param hazelcastInstance the Hazelcast instance to close server socket
     */
    protected final void tryCloseConnections(HazelcastInstance hazelcastInstance) {
        OutOfMemoryHandlerHelper.tryCloseConnections(hazelcastInstance);
    }

    /**
     * Tries to shutdown HazelcastInstance forcefully;
     * including closing sockets and connections, stopping threads, etc.
     *
     * @param hazelcastInstance the Hazelcast instance to shutdown
     */
    protected final void tryShutdown(final HazelcastInstance hazelcastInstance) {
        OutOfMemoryHandlerHelper.tryShutdown(hazelcastInstance);
    }
}