Tailer.java

/*
 * Copyright 2003-2012 Yusuke Yamamoto
 *
 * 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 samurai.tail;

import java.util.ArrayList;
import java.util.List;

public class Tailer extends Thread {
    List<SingleLogWatcher> activeWatchers = new ArrayList<SingleLogWatcher>(0);
    List<SingleLogWatcher> inactiveWatchers = new ArrayList<SingleLogWatcher>(0);
    private long lastCheck;
    private static Tailer tailer = new Tailer();

    /*package*/
    static Tailer getTailer() {
        return tailer;
    }

    private Tailer() {
        super();
        super.setName("LogWatcher Thread");
        this.setDaemon(true);
        this.setPriority(Thread.MIN_PRIORITY);
        this.start();
    }

    public synchronized void addLogWatcher(SingleLogWatcher watcher) {
        activeWatchers.add(watcher);
    }

    public void run() {
        lastCheck = System.currentTimeMillis();
        while (true) {
            for (int i = 0; i < activeWatchers.size(); i++) {
                SingleLogWatcher watcher = activeWatchers.get(i);
                watcher.checkUpdate();
                synchronized (activeWatchers) {
                    if (watcher.isDead()) {
                        activeWatchers.remove(i);
                        i--;
                    } else if (watcher.isCheckingUpdate()) {
                        inactiveWatchers.add(activeWatchers.remove(i));
                        i--;
                    }
                }
            }
            if (50 < (System.currentTimeMillis() - lastCheck)) {
//        System.out.println("check inactive watcher"+inactiveWatchers.size()+" "+activeWatchers.size());
                for (int i = 0; i < inactiveWatchers.size(); i++) {
                    SingleLogWatcher watcher = inactiveWatchers.get(i);
                    watcher.checkUpdate();
                    if (watcher.isDead()) {
                        inactiveWatchers.remove(i);
                        i--;
                    } else if (!watcher.isCheckingUpdate()) {
                        activeWatchers.add(inactiveWatchers.remove(i));
                        i--;
                    }
                }
                lastCheck = System.currentTimeMillis();
            }
            if (activeWatchers.size() == 0) {
//        System.out.println("sleep");
                try {
                    Thread.sleep(50);
                } catch (InterruptedException ie) {
                }
            }
        }
    }
}