    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     */
    017    package org.apache.logging.log4j.core.config;
    018
    019    import java.io.File;
    020    import java.util.List;
    021    import java.util.concurrent.atomic.AtomicInteger;
    022    import java.util.concurrent.locks.Lock;
    023    import 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     */
    029    public 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    }