CirmClusterStatisticsTask.java

/*******************************************************************************
 * Copyright 2014 Miami-Dade County
 * 
 * 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 org.sharegov.cirm.stats;

import java.io.IOException;
import java.util.Calendar;
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

/**
 * A task, executing every full hour to load all stats and save them in store.
 * Not thread safe yet. Handle with care.
 * 
 * @author Thomas Hilpold
 */
public class CirmClusterStatisticsTask {
    
    private static volatile CirmClusterStatisticsTask instance;
    
    private Timer timer;
    private TimerTask task;
    
    public static CirmClusterStatisticsTask getInstance(CirmClusterStatistics clusterStats, CirmClusterStatisticsStore store) {
        if (instance == null) {
            instance = new CirmClusterStatisticsTask(clusterStats, store);
        }
        return instance;
    }
    
    private CirmClusterStatisticsTask(final CirmClusterStatistics clusterStats, final CirmClusterStatisticsStore store)    {
        task = new TimerTask() {
            @Override
            public void run() {
                clusterStats.updateAll();
                try {
                    store.writeAllFrom(clusterStats);
                    System.out.println("Clusterstats auto update completed at " + new Date());
                } catch(IOException e) {
                    System.err.println("ERROR: Clusterstats auto update failed with: " + e + " at " + new Date());
                    e.printStackTrace();
                }
            }
        };
    }
   
    public void start() {
        if (timer == null) {
            timer = new Timer();
            System.out.println("Clusterstats auto update scheduling for every full hour.");
            Date nextExecutionDate = getNextFullHour();
            timer.scheduleAtFixedRate(task, nextExecutionDate, 60 * 60 * 1000);
            System.out.println("Timer started: First auto update scheduled for " + nextExecutionDate);
        } else {
            System.err.println("Timer already running");            
        }
    }
    
    public void stop() {
        timer.cancel();
        timer = null;
    }
    
    Date getNextFullHour() {
        Calendar c = Calendar.getInstance();
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);
        c.add(Calendar.HOUR, 1);
        return c.getTime();
    } 
}