ShutdownEnabledTimer.java

/*
 *
 * Copyright 2013 Netflix, 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
 *
 * 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.netflix.util.concurrent;

import java.util.Timer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 
 * ShutdownEnabledTimer class handles runtime shutdown issues.
 * 
 * Apparently, adding a runtime shutdown hook will create a global reference
 * which can cause memory leaks if not cleaned up.
 * 
 * This abstraction provides a wrapped mechanism to manage those runtime
 * shutdown hooks.
 * 
 * @author jzarfoss
 * 
 */
public class ShutdownEnabledTimer extends Timer {

    private static final Logger LOGGER = LoggerFactory
            .getLogger(ShutdownEnabledTimer.class);

    private Thread cancelThread;
    private String name;

    public ShutdownEnabledTimer(String name, boolean daemon) {
        super(name, daemon);

        this.name = name;

        this.cancelThread = new Thread(new Runnable() {
            public void run() {
                ShutdownEnabledTimer.super.cancel();
            }
        });

        LOGGER.info("Shutdown hook installed for: {}", this.name);

        Runtime.getRuntime().addShutdownHook(this.cancelThread);
    }

    @Override
    public void cancel() {
        super.cancel();

        LOGGER.info("Shutdown hook removed for: {}", this.name);

        try {
            Runtime.getRuntime().removeShutdownHook(this.cancelThread);
        } catch (IllegalStateException ise) {
            LOGGER.info("Exception caught (might be ok if at shutdown)", ise);
        }

    }

}