/*
 * Copyright 2012, 2013 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat 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, or (at your
 * option) any later version.
 *
 * Thermostat 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 Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.backend;

/**
 * This interface can be used to query the performance counters
 * of a monitored JVM when they are updated.
 * @see VmUpdateListener#countersUpdated(VmUpdate)
 */
public interface VmUpdate {

    /**
     * Queries the specified JVM performance counter with a Long data type.
     * @param name - The name of the performance counter
     * @return The current value of the requested counter, or null if no
     * such counter exists
     * @throws VmUpdateException if there is a problem communicating with
     * the JVM
     * @throws ClassCastException if the value of the counter is not a Long
     */
    Long getPerformanceCounterLong(String name) throws VmUpdateException;
    
    /**
     * Queries the specified JVM performance counter with a String data type.
     * @param name - The name of the performance counter
     * @return The current value of the requested counter, or null if no
     * such counter exists
     * @throws VmUpdateException if there is a problem communicating with
     * the JVM
     * @throws ClassCastException if the value of the counter is not a String
     */
    String getPerformanceCounterString(String name) throws VmUpdateException;
    
}