net.anotheria.util.resource.WatchDog Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of ano-util Show documentation
There is a newer version: 4.0.0
package net.anotheria.util.resource;

import net.anotheria.util.NumberUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashSet;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * WatchDog is the singleton object that register Resources and updates it on
 * underlying resource changes in defined time periods. Currently the update
 * interval is 10 seconds.
 *
 * @author another
 * @version $Id: $Id
 */
public enum WatchDog {
	/**
	 * The one and only instance of the WatchDog.
	 */
	INSTANCE(10000);

	/**
	 * Logger.
	 */
	private static Logger log = LoggerFactory.getLogger(WatchDog.class);

	private Map watchingRegistry;
	private volatile long pause;

	private WatchDog(long aPause) {
		watchingRegistry = new ConcurrentHashMap<>();
		pause = aPause;
		new WatcherThread().start();
	}

	/**
	 * Getter for the field pause.
	 *
	 * @return a long.
	 */
	public long getPause() {
		return pause;
	}

	// public void setPause(long aPause) {
	// pause = aPause;
	// }

	/**
	 * addResourceToWatch.
	 *
	 * @param resource a {@link net.anotheria.util.resource.Resource} object.
	 */
	public void addResourceToWatch(Resource resource) {
		watchingRegistry.put(resource.getName(), resource);
	}

	/**
	 * removeResourceFromWatch.
	 *
	 * @param resource a {@link net.anotheria.util.resource.Resource} object.
	 */
	public void removeResourceFromWatch(Resource resource) {
		watchingRegistry.remove(resource.getName());
	}

	/**
	 * WatcherThread runs in background and checks whether a underlying resource
	 * has been updated all X seconds. In case it did, it fires an update event
	 * triggering a Resource reloading.
	 */
	private final class WatcherThread extends Thread {

		private WatcherThread() {
			setDaemon(true);
		}

		@Override
		public void run() {
			try {
				while (!Thread.interrupted()) {
					Thread.sleep(getPause());
					Iterable watchedResources = new HashSet<>(watchingRegistry.values());
					for (Resource source : watchedResources) {
						ResourceLoader loader = source.getResourceLoader();
						try {
							long lastUpdate = loader.getLastChangeTimestamp(source.getName());
							log.debug("Checking source: {}, lastUpdateFromLoader: {}, storedLastUpdate: {}", source, NumberUtils.makeISO8601TimestampString(lastUpdate), NumberUtils.makeISO8601TimestampString(source.getLastChangeTimestamp()));
							if (source.isOlderAs(lastUpdate)) {
								log.debug("Firing update event: {}", source);
								source.fireUpdateEvent(lastUpdate);
							}
						} catch (IllegalArgumentException e) {
							log.warn("Apparently checking for non existing source, how did it came into the registry anyway?", e);
						}

					}
				}
			} catch (InterruptedException e) {
				// ignored
			}
		}
	}

}