fwservicemonitor.java

一个实用工具类

/*
 * Copyright (C) butor.com. All rights reserved.
 *
 * This software is published under the terms of the GNU Library General
 * Public License (GNU LGPL), a copy of which has been included with this
 * distribution in the LICENSE.txt file. 
 */


package org.butor.fwService.starter;

import java.util.Enumeration;
import java.util.Vector;

import org.butor.fwService.IFwServiceMonitor;
import org.butor.helper.UniqueIDGenerator;
import org.butor.log.Log;

/**
 * This class represent a thread whose sole purpose is to call
 * the isAlive() methods of the ServiceClass classes of the
 * system.  Normally, the isAlive() method is used by the
 * ServiceClass instances to check their own sanity.
 *
 * @author  Denis Benoit, aiman sawan
 */
public class FwServiceMonitor implements Runnable {
	protected Vector f_listeners;

	protected Thread f_thread = null;
	protected int f_isAlivePeriod;
	protected boolean f_shutdown = false;

	protected static FwServiceMonitor s_serviceMonitor = null;

	private static final int DEFAULT_IS_ALIVE_PERIOD = 5 * 1000; // 5 seonds
	/**
	 * FwServiceMonitor constructor.
	 */
	public FwServiceMonitor(int isAlivePeriod) {
		super();

		f_listeners = new Vector();

		f_isAlivePeriod = isAlivePeriod;
		if (isAlivePeriod < DEFAULT_IS_ALIVE_PERIOD) {
			// Sorry! Not too fast.
			f_isAlivePeriod = DEFAULT_IS_ALIVE_PERIOD;
		}

		f_thread = new Thread(this, "ServiceMonitor_" +UniqueIDGenerator.getNewId());
		if (f_thread == null) {
			Log.logStr(this, Log.LOG_TYPE_ERROR,
				"Constructor", "Could not create thread!");
			return;
		}

		s_serviceMonitor = this;
		
		// Gateways won't shut it down...
		f_thread.setDaemon(true);
		
		f_thread.start();
	}
	/**
	 * This method does an infinite loop:
	 * - Call the isAlive() method of every ServiceClass of the system;
	 * - Sleep an interval of mintNbMilliSecSleep millisecond
	 */
	public void run() {
		Log.logStr(this, Log.LOG_TYPE_INFO, "run", "isAlive check start");

		while (!f_shutdown) {
			try {
				isAlive();
				if (f_shutdown) {
					break;
				}

				Thread.sleep(f_isAlivePeriod);
				
			} catch (InterruptedException e) {
				// Just continue
			}
		}
	}
	/**
	 * This method calls the isAlive() method of every ServiceClass
	 * class of the system.
	 */
	private void isAlive() {
		Enumeration en = f_listeners.elements();
		Object oneElement = null;

		Log.logStr(
			Log.LOG_LEVEL_LOW,
			this,
			Log.LOG_TYPE_INFO,
			"isAlive",
			"Checking [" +f_listeners.size() + " service(s)] ...");
		
		synchronized (en) {
			while (en.hasMoreElements()) {
				try {
					oneElement = en.nextElement();
					((IFwServiceMonitor) oneElement).handleIsAlive();
					
				} catch (ClassCastException e) {
					Log.logStr(this, Log.LOG_TYPE_WARN, "isAlive",
						e.getMessage() + ":" + oneElement.toString());
				}
			}
		}
	}
	/**
	 * shutdown this thread.
	 */
	public void shutdown() {
		f_shutdown = true;

		synchronized (f_listeners) {
			Enumeration services = f_listeners.elements();
			Object oneElement = null;
			
			while (services.hasMoreElements()) {
				try {
					oneElement = services.nextElement();
					((IFwServiceMonitor) oneElement).shutdown();
					
				} catch (ClassCastException e) {
					Log.logStr(this, Log.LOG_TYPE_WARN, "shutdown()",
						e.getMessage() + ":" + oneElement.toString());
				}
			}
		}
		
		f_thread.interrupt();
		s_serviceMonitor = null;
		Log.logStr(this, Log.LOG_TYPE_INFO, "shutdown()", "Stopped.");
	}
	/**
	 * Register org.butor.web.listener to the keep it alive.
	 * The keep alive call back will be done fast (one each
	 * 5 seconds or so).
	 * The org.butor.web.listener must do its processing once each multiple calls.
	 * Example: Each 15 calls of handleIsAlive() the org.butor.web.listener do its
	 * processing and reset its counter.
	 */
	public static void register(IFwServiceMonitor listener) {
		Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_INFO, "register()", 
			"Registering org.butor.web.listener [" +listener +"]");
			
		if (s_serviceMonitor != null) {
			s_serviceMonitor.addListener(listener);
		} else {
			Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_WARN, "register()", 
				"Not yet initialized.");
		}
	}
	/**
	 * Unregister a org.butor.web.listener from the keep alive list.
	 */
	public static void unregister(IFwServiceMonitor listener) {
		Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_INFO, "unregister()", 
			"Unregistering org.butor.web.listener [" +listener +"]");
			
		if (s_serviceMonitor != null) {
			s_serviceMonitor.removeListener(listener);
		} else {
			Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_WARN, "unregister()", 
				"Not yet initialized.");
		}
	}
	/**
	 * Unregister a org.butor.web.listener from the keep alive list.
	 */
	public static boolean registered(IFwServiceMonitor listener) {
		Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_INFO, "registered()", 
			"registered? listenr [" +listener +"]");
			
		if (s_serviceMonitor != null) {
			return s_serviceMonitor.exists(listener);
		} else {
			Log.logStr(FwServiceMonitor.class, Log.LOG_TYPE_WARN, "registered()", 
				"Not yet initialized.");
		}
		return false;
	}
	/**
	 * Add org.butor.web.listener to the keep alive list.
	 */
	protected void addListener(IFwServiceMonitor listener) {
		if (listener == null) {
			Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_WARN, "removeListener()", 
				"Got null org.butor.web.listener!");
			return;
		}

		synchronized(f_listeners) {
			if (f_listeners.contains(listener)) {
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_WARN, "addListener()", 
					"Already added org.butor.web.listener [" +listener +"]");
			} else {
				f_listeners.add(listener);
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_INFO, "addListener()", 
					"added org.butor.web.listener [" +listener +"]");
			}
		}
	}
	/**
	 * Add org.butor.web.listener to the keep alive list.
	 */
	protected boolean exists(IFwServiceMonitor listener) {
		if (listener == null) {
			Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_WARN, "exists()", 
				"Got null org.butor.web.listener!");
			return false;
		}

		synchronized(f_listeners) {
			return (f_listeners.contains(listener));
		}
	}
	/**
	 * Remove org.butor.web.listener from the keep alive list.
	 */
	protected void removeListener(IFwServiceMonitor listener) {
		if (listener == null) {
			Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_WARN, "removeListener()", 
				"Got null org.butor.web.listener!");
			return;
		}
		
		synchronized(f_listeners) {
			if (f_listeners.contains(listener)) {
				f_listeners.remove(listener);
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_INFO, "removeListener()", 
					"removed org.butor.web.listener [" +listener +"]");
			} else {
				Log.logStr(Log.LOG_LEVEL_LOW, this, Log.LOG_TYPE_WARN, "removeListener()", 
					"Not registered org.butor.web.listener [" +listener +"]");
			}
		}
	}
}