HadoopDaemon.java

/*
 * 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.ignite.internal.processors.hadoop.impl.v2;

import java.util.Collection;
import java.util.LinkedList;

/**
 * Replacement for Hadoop {@code org.apache.hadoop.util.Daemon} class.
 */
@SuppressWarnings("UnusedDeclaration")
public class HadoopDaemon extends Thread {
    /** Lock object used for synchronization. */
    private static final Object lock = new Object();

    /** Collection to hold the threads to be stopped. */
    private static Collection<HadoopDaemon> daemons = new LinkedList<>();

    {
        setDaemon(true); // always a daemon
    }

    /** Runnable of this thread, may be this. */
    final Runnable runnable;

    /**
     * Construct a daemon thread.
     */
    public HadoopDaemon() {
        super();

        runnable = this;

        enqueueIfNeeded();
    }

    /**
     * Construct a daemon thread.
     */
    public HadoopDaemon(Runnable runnable) {
        super(runnable);

        this.runnable = runnable;

        this.setName(runnable.toString());

        enqueueIfNeeded();
    }

    /**
     * Construct a daemon thread to be part of a specified thread group.
     */
    public HadoopDaemon(ThreadGroup grp, Runnable runnable) {
        super(grp, runnable);

        this.runnable = runnable;

        this.setName(runnable.toString());

        enqueueIfNeeded();
    }

    /**
     * Getter for the runnable. May return this.
     *
     * @return the runnable
     */
    public Runnable getRunnable() {
        return runnable;
    }

    /**
     * if the runnable is a Hadoop org.apache.hadoop.hdfs.PeerCache Runnable.
     *
     * @param r the runnable.
     * @return true if it is.
     */
    private static boolean isPeerCacheRunnable(Runnable r) {
        String name = r.getClass().getName();

        return name.startsWith("org.apache.hadoop.hdfs.PeerCache");
    }

    /**
     * Enqueue this thread if it should be stopped upon the task end.
     */
    private void enqueueIfNeeded() {
        synchronized (lock) {
            if (daemons == null)
                throw new RuntimeException("Failed to create HadoopDaemon (its registry is already cleared): " +
                    "[classLoader=" + getClass().getClassLoader() + ']');

            if (runnable.getClass().getClassLoader() == getClass().getClassLoader() && isPeerCacheRunnable(runnable))
                daemons.add(this);
        }
    }

    /**
     * Stops all the registered threads.
     */
    public static void dequeueAndStopAll() {
        synchronized (lock) {
            if (daemons != null) {
                for (HadoopDaemon daemon : daemons)
                    daemon.interrupt();

                daemons = null;
            }
        }
    }
}