udpprocessor.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.net.DatagramSocket;
import java.util.Iterator;
import java.util.List;

import org.apache.log4j.Category;
import org.exolab.castor.xml.MarshalException;
import org.exolab.castor.xml.ValidationException;
import org.opennms.core.utils.ThreadCategory;
import org.opennms.netmgt.eventd.adaptors.EventHandler;
import org.opennms.netmgt.xml.event.Event;

/**
 * This class encapsulates the execution context for processing events received
 * via UDP from remote agents. This is a separate event context to allow the
 * event receiver to do minimum work to avoid dropping packets from the agents.
 * 
 * @author <a href="mailto:[e-mail]">Brian Weaver </a>
 * @author <a href="http://www.oculan.com">Oculan Corporation </a>
 * 
 */
final class UdpProcessor implements Runnable {
    /**
     * The UDP receiver thread.
     */
    private Thread m_context;

    /**
     * The list of incomming events.
     */
    private List m_eventsIn;

    /**
     * The list of outgoing event-receipts by UUID.
     */
    private List m_eventUuidsOut;

    /**
     * The list of registered event handlers.
     */
    private List m_handlers;

    /**
     * The stop flag
     */
    private volatile boolean m_stop;

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

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

    UdpProcessor(List handlers, List in, List out) {
        m_context = null;
        m_stop = false;
        m_eventsIn = in;
        m_eventUuidsOut = out;
        m_handlers = handlers;
        m_logPrefix = org.opennms.netmgt.eventd.Eventd.LOG4J_CATEGORY;
    }

    /**
     * Returns true if the thread is still alive
     */
    boolean isAlive() {
        return (m_context == null ? false : m_context.isAlive());
    }

    /**
     * Stops the current context
     */
    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");
        }
    }

    /**
     * The event processing execution context.
     */
    public void run() {
        // The runnable context
        //
        m_context = Thread.currentThread();

        // get a logger
        //
        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");

        // This loop is labeled so that it can be
        // exited quickly when the thread is interrupted
        //
        RunLoop: while (!m_stop) {
            if (isTracing)
                log.debug("Waiting on a new datagram to arrive");

            UdpReceivedEvent re = null;
            synchronized (m_eventsIn) {
                // wait for an event to show up.
                // wait in 1/2 second intervals
                //
                while (m_eventsIn.isEmpty()) {
                    try {
                        m_eventsIn.wait(500);
                    } catch (InterruptedException ie) {
                        if (isTracing)
                            log.debug("Thread interrupted");
                        break RunLoop;
                    }

                    if (m_stop) {
                        if (isTracing)
                            log.debug("Stop flag is set");
                        break RunLoop;
                    }
                }
                re = (UdpReceivedEvent) m_eventsIn.remove(0);
            }

            if (isTracing)
                log.debug("A new request has arrived");

            // Convert the Event
            //
            Event[] events = null;
            try {
                if (isTracing) {
                    log.debug("Event from " + re.getSender().getHostAddress() + ":" + re.getPort());
                    log.debug("Unmarshalling Event text {" + System.getProperty("line.separator") + re.getXmlData() + System.getProperty("line.separator") + "}");
                }
                events = re.unmarshal().getEvents().getEvent();
            } catch (MarshalException e) {
                log.warn("Failed to unmarshal the event from " + re.getSender().getHostAddress() + ":" + re.getPort(), e);
                continue;
            } catch (ValidationException e) {
                log.warn("Failed to validate the event from " + re.getSender().getHostAddress() + ":" + re.getPort(), e);
                continue;
            }

            if (events == null || events.length == 0) {
                if (isTracing)
                    log.debug("The event log record contained no events");
                continue;
            } else if (isTracing) {
                log.debug("Processing " + events.length + " events");
            }

            // process the event
            //
            synchronized (m_handlers) {
                // get the list of events from the event log.
                // Also, get an iterator to walk over the set
                // of event handlers
                //
                Iterator iter = m_handlers.iterator();
                while (iter.hasNext()) {
                    // iterate over the list of the events
                    // from the received documents.
                    //
                    for (int ndx = 0; ndx < events.length; ndx++) {
                        try {
                            // shortcut and, both sides of the and statment WILL
                            // execute
                            // regardless of the other side's value
                            //
                            if (((EventHandler) iter.next()).processEvent(events[ndx])) {
                                re.ackEvent(events[ndx]);
                            }
                        } catch (Throwable t) {
                            log.warn("Failed to process received UDP event, exception follows", t);
                        }

                    } // end event processing loop

                } // end handler loop
            }

            if (isTracing)
                log.debug("event processing complete, forwarding to receipt generator");

            synchronized (m_eventUuidsOut) {
                m_eventUuidsOut.add(re);
                // Don't notify, let them batch up!
            }

        } // end RunLoop

        if (isTracing)
            log.debug("Context finished, returning");

    } // end run()

    void setLogPrefix(String prefix) {
        m_logPrefix = prefix;
    }
} // end EventProcessor Class