/*

 * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package javax.management.monitor;

import static com.sun.jmx.defaults.JmxProperties.MONITOR_LOGGER;

import com.sun.jmx.mbeanserver.GetPropertyAction;

import com.sun.jmx.mbeanserver.Introspector;

import java.io.IOException;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.security.ProtectionDomain;

import java.util.List;

import java.util.Map;

import java.util.WeakHashMap;

import java.util.concurrent.CopyOnWriteArrayList;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

import java.util.concurrent.LinkedBlockingQueue;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.ScheduledFuture;

import java.util.concurrent.ThreadFactory;

import java.util.concurrent.ThreadPoolExecutor;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicInteger;

import java.util.concurrent.atomic.AtomicLong;

import java.lang.System.Logger.Level;

import javax.management.AttributeNotFoundException;

import javax.management.InstanceNotFoundException;

import javax.management.IntrospectionException;

import javax.management.MBeanAttributeInfo;

import javax.management.MBeanException;

import javax.management.MBeanInfo;

import javax.management.MBeanRegistration;

import javax.management.MBeanServer;

import javax.management.MBeanServerConnection;

import javax.management.NotificationBroadcasterSupport;

import javax.management.ObjectName;

import javax.management.ReflectionException;

import static javax.management.monitor.MonitorNotification.*;

/**

 * Defines the part common to all monitor MBeans.

 * A monitor MBean monitors values of an attribute common to a set of observed

 * MBeans. The observed attribute is monitored at intervals specified by the

 * granularity period. A gauge value (derived gauge) is derived from the values

 * of the observed attribute.

 *

 *

 * @since 1.5

 */

public abstract class Monitor

    extends NotificationBroadcasterSupport

    implements MonitorMBean, MBeanRegistration {

    /*

     * ------------------------------------------

     *  PACKAGE CLASSES

     * ------------------------------------------

     */

    static class ObservedObject {

        public ObservedObject(ObjectName observedObject) {

            this.observedObject = observedObject;

        }

        public final ObjectName getObservedObject() {

            return observedObject;

        }

        public final synchronized int getAlreadyNotified() {

            return alreadyNotified;

        }

        public final synchronized void setAlreadyNotified(int alreadyNotified) {

            this.alreadyNotified = alreadyNotified;

        }

        public final synchronized Object getDerivedGauge() {

            return derivedGauge;

        }

        public final synchronized void setDerivedGauge(Object derivedGauge) {

            this.derivedGauge = derivedGauge;

        }

        public final synchronized long getDerivedGaugeTimeStamp() {

            return derivedGaugeTimeStamp;

        }

        public final synchronized void setDerivedGaugeTimeStamp(

                                                 long derivedGaugeTimeStamp) {

            this.derivedGaugeTimeStamp = derivedGaugeTimeStamp;

        }

        private final ObjectName observedObject;

        private int alreadyNotified;

        private Object derivedGauge;

        private long derivedGaugeTimeStamp;

    }

    /*

     * ------------------------------------------

     *  PRIVATE VARIABLES

     * ------------------------------------------

     */

    /**

     * Attribute to observe.

     */

    private String observedAttribute;

    /**

     * Monitor granularity period (in milliseconds).

     * The default value is set to 10 seconds.

     */

    private long granularityPeriod = 10000;

    /**

     * Monitor state.

     * The default value is set to <CODE>false</CODE>.

     */

    private boolean isActive = false;

    /**

     * Monitor sequence number.

     * The default value is set to 0.

     */

    private final AtomicLong sequenceNumber = new AtomicLong();

    /**

     * Complex type attribute flag.

     * The default value is set to <CODE>false</CODE>.

     */

    private boolean isComplexTypeAttribute = false;

    /**

     * First attribute name extracted from complex type attribute name.

     */

    private String firstAttribute;

    /**

     * Remaining attribute names extracted from complex type attribute name.

     */

    private final List<String> remainingAttributes =

        new CopyOnWriteArrayList<String>();

    /**

     * AccessControlContext of the Monitor.start() caller.

     */

    private static final AccessControlContext noPermissionsACC =

            new AccessControlContext(

            new ProtectionDomain[] {new ProtectionDomain(null, null)});

    private volatile AccessControlContext acc = noPermissionsACC;

    /**

     * Scheduler Service.

     */

    private static final ScheduledExecutorService scheduler =

        Executors.newSingleThreadScheduledExecutor(

            new DaemonThreadFactory("Scheduler"));

    /**

     * Map containing the thread pool executor per thread group.

     */

    private static final Map<ThreadPoolExecutor, Void> executors =

            new WeakHashMap<ThreadPoolExecutor, Void>();

    /**

     * Lock for executors map.

     */

    private static final Object executorsLock = new Object();

    /**

     * Maximum Pool Size

     */

    private static final int maximumPoolSize;

    static {

        final String maximumPoolSizeSysProp = "jmx.x.monitor.maximum.pool.size";

        final String maximumPoolSizeStr = AccessController.doPrivileged(

            new GetPropertyAction(maximumPoolSizeSysProp));

        if (maximumPoolSizeStr == null ||

            maximumPoolSizeStr.trim().length() == 0) {

            maximumPoolSize = 10;

        } else {

            int maximumPoolSizeTmp = 10;

            try {

                maximumPoolSizeTmp = Integer.parseInt(maximumPoolSizeStr);

            } catch (NumberFormatException e) {

                if (MONITOR_LOGGER.isLoggable(Level.TRACE)) {

                    MONITOR_LOGGER.log(Level.TRACE,

                            "Wrong value for " + maximumPoolSizeSysProp +

                            " system property", e);

                    MONITOR_LOGGER.log(Level.TRACE,

                            maximumPoolSizeSysProp + " defaults to 10");

                }

                maximumPoolSizeTmp = 10;

            }

            if (maximumPoolSizeTmp < 1) {

                maximumPoolSize = 1;

            } else {

                maximumPoolSize = maximumPoolSizeTmp;

            }

        }

    }

    /**

     * Future associated to the current monitor task.

     */

    private Future<?> monitorFuture;

    /**

     * Scheduler task to be executed by the Scheduler Service.

     */

    private final SchedulerTask schedulerTask = new SchedulerTask();

    /**

     * ScheduledFuture associated to the current scheduler task.

     */

    private ScheduledFuture<?> schedulerFuture;

    /*

     * ------------------------------------------

     *  PROTECTED VARIABLES

     * ------------------------------------------

     */

    /**

     * The amount by which the capacity of the monitor arrays are

     * automatically incremented when their size becomes greater than

     * their capacity.

     */

    protected final static int capacityIncrement = 16;

    /**

     * The number of valid components in the vector of observed objects.

     *

     */

    protected int elementCount = 0;

    /**

     * Monitor errors that have already been notified.

     * @deprecated equivalent to {@link #alreadyNotifieds}[0].

     */

    @Deprecated

    protected int alreadyNotified = 0;

    /**

     * <p>Selected monitor errors that have already been notified.</p>

     *

     * <p>Each element in this array corresponds to an observed object

     * in the vector.  It contains a bit mask of the flags {@link

     * #OBSERVED_OBJECT_ERROR_NOTIFIED} etc, indicating whether the

     * corresponding notification has already been sent for the MBean

     * being monitored.</p>

     *

     */

    protected int alreadyNotifieds[] = new int[capacityIncrement];

    /**

     * Reference to the MBean server.  This reference is null when the

     * monitor MBean is not registered in an MBean server.  This

     * reference is initialized before the monitor MBean is registered

     * in the MBean server.

     * @see #preRegister(MBeanServer server, ObjectName name)

     */

    protected MBeanServer server;

    // Flags defining possible monitor errors.

    //

    /**

     * This flag is used to reset the {@link #alreadyNotifieds

     * alreadyNotifieds} monitor attribute.

     */

    protected static final int RESET_FLAGS_ALREADY_NOTIFIED             = 0;

    /**

     * Flag denoting that a notification has occurred after changing

     * the observed object.  This flag is used to check that the new

     * observed object is registered in the MBean server at the time

     * of the first notification.

     */

    protected static final int OBSERVED_OBJECT_ERROR_NOTIFIED           = 1;

    /**

     * Flag denoting that a notification has occurred after changing

     * the observed attribute.  This flag is used to check that the

     * new observed attribute belongs to the observed object at the

     * time of the first notification.

     */

    protected static final int OBSERVED_ATTRIBUTE_ERROR_NOTIFIED        = 2;

    /**

     * Flag denoting that a notification has occurred after changing

     * the observed object or the observed attribute.  This flag is

     * used to check that the observed attribute type is correct

     * (depending on the monitor in use) at the time of the first

     * notification.

     */

    protected static final int OBSERVED_ATTRIBUTE_TYPE_ERROR_NOTIFIED   = 4;

    /**

     * Flag denoting that a notification has occurred after changing

     * the observed object or the observed attribute.  This flag is

     * used to notify any exception (except the cases described above)

     * when trying to get the value of the observed attribute at the

     * time of the first notification.

     */

    protected static final int RUNTIME_ERROR_NOTIFIED                   = 8;

    /**

     * This field is retained for compatibility but should not be referenced.

     *

     * @deprecated No replacement.

     */

    @Deprecated

    protected String dbgTag = Monitor.class.getName();

    /*

     * ------------------------------------------

     *  PACKAGE VARIABLES

     * ------------------------------------------

     */

    /**

     * List of ObservedObjects to which the attribute to observe belongs.

     */

    final List<ObservedObject> observedObjects =

        new CopyOnWriteArrayList<ObservedObject>();

    /**

     * Flag denoting that a notification has occurred after changing

     * the threshold. This flag is used to notify any exception

     * related to invalid thresholds settings.

     */

    static final int THRESHOLD_ERROR_NOTIFIED                           = 16;

    /**

     * Enumeration used to keep trace of the derived gauge type

     * in counter and gauge monitors.

     */

    enum NumericalType { BYTE, SHORT, INTEGER, LONG, FLOAT, DOUBLE };

    /**

     * Constant used to initialize all the numeric values.

     */

    static final Integer INTEGER_ZERO = 0;

    /*

     * ------------------------------------------

     *  PUBLIC METHODS

     * ------------------------------------------

     */

    /**

     * Allows the monitor MBean to perform any operations it needs

     * before being registered in the MBean server.

     * <P>

     * Initializes the reference to the MBean server.

     *

     * @param server The MBean server in which the monitor MBean will

     * be registered.

     * @param name The object name of the monitor MBean.

     *

     * @return The name of the monitor MBean registered.

     *

     * @exception Exception if something goes wrong

     */

    public ObjectName preRegister(MBeanServer server, ObjectName name)

        throws Exception {

        MONITOR_LOGGER.log(Level.TRACE,

                "initialize the reference on the MBean server");

        this.server = server;

        return name;

    }

    /**

     * Allows the monitor MBean to perform any operations needed after

     * having been registered in the MBean server or after the

     * registration has failed.

     * <P>

     * Not used in this context.

     */

    public void postRegister(Boolean registrationDone) {

    }

    /**

     * Allows the monitor MBean to perform any operations it needs

     * before being unregistered by the MBean server.

     * <P>

     * Stops the monitor.

     *

     * @exception Exception if something goes wrong

     */

    public void preDeregister() throws Exception {

        MONITOR_LOGGER.log(Level.TRACE, "stop the monitor");

        // Stop the Monitor.

        //

        stop();

    }

    /**

     * Allows the monitor MBean to perform any operations needed after

     * having been unregistered by the MBean server.

     * <P>

     * Not used in this context.

     */

    public void postDeregister() {

    }

    /**

     * Starts the monitor.

     */

    public abstract void start();

    /**

     * Stops the monitor.

     */

    public abstract void stop();

    // GETTERS AND SETTERS

    //--------------------

    /**

     * Returns the object name of the first object in the set of observed

     * MBeans, or <code>null</code> if there is no such object.

     *

     * @return The object being observed.

     *

     * @see #setObservedObject(ObjectName)

     *

     * @deprecated As of JMX 1.2, replaced by {@link #getObservedObjects}

     */

    @Deprecated

    public synchronized ObjectName getObservedObject() {

        if (observedObjects.isEmpty()) {

            return null;

        } else {

            return observedObjects.get(0).getObservedObject();

        }

    }

    /**

     * Removes all objects from the set of observed objects, and then adds the

     * specified object.

     *

     * @param object The object to observe.

     * @exception IllegalArgumentException The specified

     * object is null.

     *

     * @see #getObservedObject()

     *

     * @deprecated As of JMX 1.2, replaced by {@link #addObservedObject}

     */

    @Deprecated

    public synchronized void setObservedObject(ObjectName object)

        throws IllegalArgumentException {

        if (object == null)

            throw new IllegalArgumentException("Null observed object");

        if (observedObjects.size() == 1 && containsObservedObject(object))

            return;

        observedObjects.clear();

        addObservedObject(object);

    }

    /**

     * Adds the specified object in the set of observed MBeans, if this object

     * is not already present.

     *

     * @param object The object to observe.

     * @exception IllegalArgumentException The specified object is null.

     *

     */

    public synchronized void addObservedObject(ObjectName object)

        throws IllegalArgumentException {

        if (object == null) {

            throw new IllegalArgumentException("Null observed object");

        }

        // Check that the specified object is not already contained.

        //

        if (containsObservedObject(object))

            return;

        // Add the specified object in the list.

        //

        ObservedObject o = createObservedObject(object);

        o.setAlreadyNotified(RESET_FLAGS_ALREADY_NOTIFIED);

        o.setDerivedGauge(INTEGER_ZERO);

        o.setDerivedGaugeTimeStamp(System.currentTimeMillis());

        observedObjects.add(o);

        // Update legacy protected stuff.

        //

        createAlreadyNotified();

    }

    /**

     * Removes the specified object from the set of observed MBeans.