WorkerService.java

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors 
 * as indicated by the @author tags. 
 * See the copyright.txt in the distribution for a
 * full listing of individual contributors. 
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License, v. 2.1.
 * This program is distributed in the hope that it will be useful, but WITHOUT A 
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A 
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public License,
 * v.2.1 along with this distribution; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
 * MA  02110-1301, USA.
 * 
 * (C) 2005-2006,
 * @author JBoss Inc.
 */
/*
 * Copyright (C) 2003,
 *
 * Arjuna Technologies Ltd,
 * Newcastle upon Tyne,
 * Tyne and Wear,
 * UK.
 *
 * $Id: WorkerService.java 2342 2006-03-30 13:06:17Z  $
 */
 
package com.arjuna.ats.internal.arjuna.recovery;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;

import com.arjuna.ats.arjuna.logging.tsLogger;
import com.arjuna.ats.arjuna.recovery.RecoveryDriver;
import com.arjuna.ats.arjuna.recovery.Service;

public class WorkerService implements Service
{
    public WorkerService (PeriodicRecovery pr)
    {
	_periodicRecovery = pr;
    }
    
    public void doWork (InputStream is, OutputStream os) throws IOException
    {
	BufferedReader in  = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8));
	PrintWriter out = new PrintWriter(new OutputStreamWriter(os, StandardCharsets.UTF_8));

	try
	{
	    String request = in.readLine();

        if (request.equals("PING"))
        {
            out.println("PONG");
        }
        else
	    if (request.equals(RecoveryDriver.SCAN) || (request.equals(RecoveryDriver.ASYNC_SCAN)))
	    {
            // hmm, we need to synchronize on the periodic recovery object in order to wake it up via notify.
            // but the periodic recovery object has to synchronize on this object and then call notify
            // in order to tell it that the last requested scan has completed. i.e. we have a two way
            // wakeup here. so we have to be careful to avoid a deadlock.

            if (request.equals(RecoveryDriver.SCAN)) {
                // do this before kicking the periodic recovery thread
                synchronized (this) {
                    doWait = true;
                }
            }
            // now we only need to hold one lock
		_periodicRecovery.wakeUp();

            tsLogger.i18NLogger.info_recovery_WorkerService_3();

		if (request.equals(RecoveryDriver.SCAN))
		{
            synchronized (this) {
                if (doWait) {
                    // ok, the periodic recovery thread cannot have finished responding to the last scan request
                    // so it is safe to wait. if we delivered the request while the last scan was still going
                    // then it will have been ignored but that is ok.
		    try
		    {
			wait();
		    }
		    catch (Exception ex)
		    {
                tsLogger.i18NLogger.info_recovery_WorkerService_4();
		    }
                }
            }
		}
		out.println("DONE");
	    }
	    else
		out.println("ERROR");

	    out.flush();
	}
	catch (IOException ex) {
        tsLogger.i18NLogger.warn_recovery_WorkerService_2();
    }
	catch ( Exception ex ) {
        tsLogger.i18NLogger.warn_recovery_WorkerService_1(ex);
    }
    }

    public synchronized void notifyDone()
    {
	try
	{
	    notifyAll();
        doWait = false;
	}
	catch (Exception ex)
	{
	}
    }

    private PeriodicRecovery _periodicRecovery = null;
    private boolean doWait = false;

}