001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.config;
018
019import java.io.File;
020import java.util.List;
021import java.util.concurrent.atomic.AtomicInteger;
022import java.util.concurrent.locks.Lock;
023import java.util.concurrent.locks.ReentrantLock;
024
025/**
026 * Configuration monitor that periodically checks the timestamp of the configuration file and calls the
027 * ConfigurationListeners when an update occurs.
028 */
029public class FileConfigurationMonitor implements ConfigurationMonitor {
030
031    private static final int MASK = 0x0f;
032
033    private static final int MIN_INTERVAL = 5;
034
035    private static final int MILLIS_PER_SECOND = 1000;
036
037    private final File file;
038
039    private long lastModified;
040
041    private final List<ConfigurationListener> listeners;
042
043    private final int intervalSeconds;
044
045    private long nextCheck;
046
047    private final AtomicInteger counter = new AtomicInteger(0);
048
049    private static final Lock LOCK = new ReentrantLock();
050
051    private final Reconfigurable reconfigurable;
052
053    /**
054     * Constructor.
055     * @param reconfigurable The Configuration that can be reconfigured.
056     * @param file The File to monitor.
057     * @param listeners The List of ConfigurationListeners to notify upon a change.
058     * @param intervalSeconds The monitor interval in seconds. The minimum interval is 5 seconds.
059     */
060    public FileConfigurationMonitor(final Reconfigurable reconfigurable, final File file,
061                                    final List<ConfigurationListener> listeners,
062                                    final int intervalSeconds) {
063        this.reconfigurable = reconfigurable;
064        this.file = file;
065        this.lastModified = file.lastModified();
066        this.listeners = listeners;
067        this.intervalSeconds = (intervalSeconds < MIN_INTERVAL ? MIN_INTERVAL : intervalSeconds) * MILLIS_PER_SECOND;
068        this.nextCheck = System.currentTimeMillis() + intervalSeconds;
069    }
070
071    /**
072     * Called to determine if the configuration has changed.
073     */
074    @Override
075    public void checkConfiguration() {
076        final long current = System.currentTimeMillis();
077        if (((counter.incrementAndGet() & MASK) == 0) && (current >= nextCheck)) {
078            LOCK.lock();
079            try {
080                nextCheck = current + intervalSeconds;
081                if (file.lastModified() > lastModified) {
082                    lastModified = file.lastModified();
083                    for (final ConfigurationListener listener : listeners) {
084                        final Thread thread = new Thread(new ReconfigurationWorker(listener, reconfigurable));
085                        thread.setDaemon(true);
086                        thread.start();
087                    }
088                }
089            } finally {
090                LOCK.unlock();
091            }
092        }
093    }
094
095    private class ReconfigurationWorker implements Runnable {
096
097        private final ConfigurationListener listener;
098        private final Reconfigurable reconfigurable;
099
100        public ReconfigurationWorker(final ConfigurationListener listener, final Reconfigurable reconfigurable) {
101            this.listener = listener;
102            this.reconfigurable = reconfigurable;
103        }
104
105        @Override
106        public void run() {
107            listener.onChange(reconfigurable);
108        }
109    }
110}