udpreceiver.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Modifications:
//
// 2003 Jan 31: Cleaned up some unused imports.
//
// Original code base Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.                                                            
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//       
// For more information contact: 
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//

package org.opennms.netmgt.eventd.adaptors.udp;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.UnsupportedEncodingException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.List;

import org.apache.log4j.Category;
import org.opennms.core.utils.ThreadCategory;

/**
 * 
 * @author <a href="mailto:[e-mail]">Brian Weaver </a>
 * @author <a href="http://www.oculan.com">Oculan Corporation </a>
 * 
 */
class UdpReceiver implements Runnable {
    /**
     * The list of incomming events.
     */
    private List m_eventsIn;

    /**
     * The Fiber's status.
     */
    private volatile boolean m_stop;

    /**
     * The UDP socket for receipt and transmission of packets from agents.
     */
    private DatagramSocket m_dgSock;

    /**
     * The context thread
     */
    private Thread m_context;

    /**
     * The log prefix
     */
    private String m_logPrefix;

    /**
     * construct a new receiver
     */
    UdpReceiver(DatagramSocket sock, List xchange) {
        m_eventsIn = xchange;
        m_stop = false;
        m_dgSock = sock;
        m_logPrefix = org.opennms.netmgt.eventd.Eventd.LOG4J_CATEGORY;
    }

    /**
     * stop the current receiver
     */
    void stop() throws InterruptedException {
        m_stop = true;
        if (m_context != null) {
            Category log = ThreadCategory.getInstance(getClass());
            if (log.isDebugEnabled())
                log.debug("Stopping and joining thread context " + m_context.getName());

            m_context.interrupt();
            m_context.join();

            if (log.isDebugEnabled())
                log.debug("Thread context stopped and joined");
        }
    }

    /**
     * Return true if this receiver is alive
     */
    boolean isAlive() {
        return (m_context == null ? false : m_context.isAlive());
    }

    /**
     * The execution context.
     */
    public void run() {
        // get the context
        //
        m_context = Thread.currentThread();

        // Get a log instance
        //
        ThreadCategory.setPrefix(m_logPrefix);
        Category log = ThreadCategory.getInstance(getClass());
        boolean isTracing = log.isDebugEnabled();

        if (m_stop) {
            if (isTracing)
                log.debug("Stop flag set before thread started, exiting");
            return;
        } else if (isTracing)
            log.debug("Thread context started");

        // allocate a buffer
        //
        final int length = 0xffff;
        final byte[] buffer = new byte[length];
        DatagramPacket pkt = new DatagramPacket(buffer, length);

        // set an SO timout to make sure we don't block forever
        // if a socket is closed.
        //
        try {
            if (isTracing)
                log.debug("Setting socket timeout to 500ms");

            m_dgSock.setSoTimeout(500);
        } catch (SocketException e) {
            log.warn("An I/O error occured while trying to set the socket timeout", e);
        }

        // Increase the receive buffer for the
        // socket
        //
        try {
            if (isTracing)
                log.debug("Setting receive buffer size to " + length);

            m_dgSock.setReceiveBufferSize(length);
        } catch (SocketException e) {
            log.info("Failed to set the receive buffer to " + length, e);
        }

        // set to avoid numerious tracing message
        // 
        boolean ioInterrupted = false;

        // now start processing incomming request
        //
        while (!m_stop) {
            if (m_context.isInterrupted()) {
                if (isTracing)
                    log.debug("Thread context interrupted");

                break;
            }

            try {
                if (isTracing && !ioInterrupted)
                    log.debug("Wating on a datagram to arrive");

                m_dgSock.receive(pkt);
                ioInterrupted = false; // reset the flag
            } catch (InterruptedIOException e) {
                ioInterrupted = true;
                continue;
            } catch (IOException e) {
                log.error("An I/O exception occured on the datagram receipt port, exiting", e);
                break;
            }

            try {
                if (isTracing)
                    log.debug("Sending received packet to processor");

                UdpReceivedEvent re = UdpReceivedEvent.make(pkt);
                synchronized (m_eventsIn) {
                    m_eventsIn.add(re);
                    m_eventsIn.notify();
                }
            } catch (UnsupportedEncodingException e) {
                log.warn("Failed to convert received XML event, discarding", e);
            }

            pkt = new DatagramPacket(buffer, length);

        } // end while status ok

        if (isTracing)
            log.debug("Thread context exiting");

    } // end run method

    void setLogPrefix(String prefix) {
        m_logPrefix = prefix;
    }

} // end class