SnmpWalker.java

//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2005 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.
//
// 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       <license@opennms.org>
//     http://www.opennms.org/
//     http://www.opennms.com/
//
package org.infosec.ismp.snmp;

import java.io.IOException;
import java.net.InetAddress;

import org.infosec.ismp.util.ThreadCategory;
import org.infosec.ismp.util.concurrent.BarrierSignaler;

public abstract class SnmpWalker {

	protected static abstract class WalkerPduBuilder extends PduBuilder {
		protected WalkerPduBuilder(int maxVarsPerPdu) {
			super(maxVarsPerPdu);
		}

		abstract public void reset();
	}

	private final String m_name;
	private final CollectionTracker m_tracker;

	private final BarrierSignaler m_signal;

	private InetAddress m_address;
	private WalkerPduBuilder m_pduBuilder;
	private ResponseProcessor m_responseProcessor;
	private final int m_maxVarsPerPdu;
	private boolean m_error = false;
	private String m_errorMessage;
	private Throwable m_errorThrowable;

	protected SnmpWalker(InetAddress address, String name, int maxVarsPerPdu,
			int maxRepititions, CollectionTracker tracker) {
		m_address = address;
		m_signal = new BarrierSignaler(1);

		m_name = name;

		m_tracker = tracker;
		m_tracker.setMaxRepetitions(maxRepititions);

		m_maxVarsPerPdu = maxVarsPerPdu;

	}

	protected abstract WalkerPduBuilder createPduBuilder(int maxVarsPerPdu);

	public void start() {
		m_pduBuilder = createPduBuilder(m_maxVarsPerPdu);
		try {
			buildAndSendNextPdu();
		} catch (Throwable e) {
			handleFatalError(e);
		}
	}

	public int getMaxVarsPerPdu() {
		return (m_pduBuilder == null ? m_maxVarsPerPdu : m_pduBuilder
				.getMaxVarsPerPdu());
	}

	protected void buildAndSendNextPdu() throws IOException {
		if (m_tracker.isFinished()) {
			handleDone();
		} else {
			m_pduBuilder.reset();
			m_responseProcessor = m_tracker.buildNextPdu(m_pduBuilder);
			sendNextPdu(m_pduBuilder);
		}
	}

	protected abstract void sendNextPdu(WalkerPduBuilder pduBuilder)
			throws IOException;

	protected void handleDone() {
		finish();
	}

	/**
	 * <P>
	 * Returns the success or failure code for collection of the data.
	 * </P>
	 */
	public boolean failed() {
		return m_error;
	}

	public boolean timedOut() {
		return m_tracker.timedOut();
	}

	protected void handleAuthError(String msg) {
		m_tracker.setFailed(true);
		processError("Authentication error processing", msg, null);
	}

	protected void handleError(String msg) {
		// XXX why do we set timedOut to false here? should we be doing this
		// everywhere?
		m_tracker.setTimedOut(false);
		processError("Error retrieving", msg, null);
	}

	protected void handleFatalError(Throwable e) {
		m_tracker.setFailed(true);
		processError("Unexpected error occurred processing", e.toString(), e);
	}

	protected void handleTimeout(String msg) {
		m_tracker.setTimedOut(true);
		processError("Timeout retrieving", msg, null);
	}

	private void processError(String reason, String cause, Throwable t) {
		String logMessage = reason + " " + getName() + " for " + m_address
				+ ": " + cause;

		m_error = true;
		m_errorMessage = logMessage;
		m_errorThrowable = t;

		finish();
	}

	private void finish() {
		signal();
		try {
			close();
		} catch (IOException e) {
			log().error(
					getName()
							+ ": Unexpected Error occured closing snmp session for: "
							+ m_address, e);
		}
	}

	protected abstract void close() throws IOException;

	public String getName() {
		return m_name;
	}

	private void signal() {
		synchronized (this) {
			notifyAll();
		}
		if (m_signal != null) {
			m_signal.signalAll();
		}
	}

	private final ThreadCategory log() {
		return ThreadCategory.getInstance(SnmpWalker.class);
	}

	public void waitFor() throws InterruptedException {
		m_signal.waitFor();
	}

	public void waitFor(long timeout) throws InterruptedException {
		m_signal.waitFor(timeout);
	}

	protected boolean processErrors(int errorStatus, int errorIndex) {
		return m_responseProcessor.processErrors(errorStatus, errorIndex);
	}

	protected void processResponse(SnmpObjId receivedOid, SnmpValue val) {
		m_responseProcessor.processResponse(receivedOid, val);
	}

	protected void setAddress(InetAddress address) {
		m_address = address;
	}

	protected InetAddress getAddress() {
		return m_address;
	}

	public String getErrorMessage() {
		return m_errorMessage;
	}

	public Throwable getErrorThrowable() {
		return m_errorThrowable;
	}

}