ServiceMonitor.java

package org.infosec.ismp.model.poller;

import java.util.Map;


/**
 * <p>
 * This is the interface that must be implemented by each poller plugin in the
 * framework. This well defined interface allows the framework to treat each
 * plugin identically.
 * </p>
 * 
 * <p>
 * When a service monitor plug-in is loaded and initialized, the framework will
 * initialize the monitor by calling the <EM>initialize()</EM> method.
 * Likewise, when the monitor is unloaded the framework calls the <EM>release()
 * </EM> method is called. If the plug-in needs to save or read any
 * configuration information after the initialize() call, a reference to the
 * proxy object should be saved at initialization.
 * </p>
 * 
 * <P>
 * <STRONG>NOTE: </STRONG> The plug-in <EM>poll()</EM> must be thread safe in
 * order to operate. Any synchronized methods or data accessed in the <EM>
 * poll()</EM> can negatively affect the framework if multiple poller threads
 * are blocked on a critical resource. Synchronization issues should be
 * seriously evaluated to ensure that the plug-in scales well to large
 * deployments.
 * </P>
 * 
 */
public interface ServiceMonitor {

	/**
	 * <P>
	 * This method is called after the framework creates an instance of the
	 * plug-in. The framework passes the object a proxy object that can be used
	 * to retrieve configuration information specific to the plug-in.
	 * Additionally, any parameters for the plug-in from the package definition
	 * are passed using the parameters element.
	 * </P>
	 * 
	 * <P>
	 * If there is a critical error, like missing service libraries, the the
	 * Monitor may throw a ServiceMonitorException. If the plug-in throws an
	 * exception then the plug-in will be disabled in the framework.
	 * </P>
	 * @param parameters
	 *            Not currently used
	 * 
	 * @exception java.lang.RuntimeException
	 *                Thrown if an unrecoverable error occurs that prevents the
	 *                plug-in from functioning.
	 * 
	 */
	public void initialize(Map<String, Object> parameters);

	/**
	 * <P>
	 * This method is called whenever the plug-in is being unloaded, normally
	 * during framework exit. During this time the framework may release any
	 * resource and save any state information using the proxy object from the
	 * initialization routine.
	 * </P>
	 * 
	 * <P>
	 * Even if the plug-in throws a monitor exception, it will not prevent the
	 * plug-in from being unloaded. The plug-in should not return until all of
	 * its state information is saved. Once the plug-in returns from this call
	 * its configuration proxy object is considered invalid.
	 * </P>
	 * 
	 * @exception java.lang.RuntimeException
	 *                Thrown if an error occurs during deallocation.
	 * 
	 */
	public void release();

	/**
	 * <P>
	 * This method is called whenever a new interface that supports the plug-in
	 * service is added to the scheduling system. The plug-in has the option to
	 * load and/or associate configuration information with the interface before
	 * the framework begins scheduling the new device.
	 * </P>
	 * 
	 * <P>
	 * Should a monitor exception be thrown during an initialization call then
	 * the framework will log an error and discard the interface from
	 * scheduling.
	 * </P>
	 * @param svc TODO
	 * 
	 * @exception java.lang.RuntimeException
	 *                Thrown if an unrecoverable error occurs that prevents the
	 *                interface from being monitored.
	 * @exception
	 *                org.opennms.netmgt.poller.NetworkInterfaceNotSupportedException
	 *                Thrown if the passed interface is invalid for this
	 *                monitor.
	 * 
	 */
	public void initialize(MonitoredService svc);

	/**
	 * <P>
	 * This method is the called whenever an interface is being removed from the
	 * scheduler. For example, if a service is determined as being no longer
	 * supported then this method will be invoked to cleanup any information
	 * associated with this device. This gives the implementor of the interface
	 * the ability to serialize any data prior to the interface being discarded.
	 * </P>
	 * 
	 * <P>
	 * If an exception is thrown during the release the exception will be
	 * logged, but the interface will still be discarded for garbage collection.
	 * </P>
	 * @param svc TODO
	 * 
	 * @exception java.lang.RuntimeException
	 *                Thrown if an unrecoverable error occurs that prevents the
	 *                interface from being monitored.
	 */
	public void release(MonitoredService svc);

	/**
	 * <P>
	 * This method is the heart of the plug-in monitor. Each time an interface
	 * requires a check to be performed as defined by the scheduler the poll
	 * method is invoked. The poll is passed the interface to check
	 * </P>
	 * 
	 * <P>
	 * By default when the status transition from up to down or vice versa the
	 * framework will generate an event. Additionally, if the polling interval
	 * changes due to an extended unavailability, the framework will generate an
	 * additional down event. The plug-in can suppress the generation of the
	 * default events by setting the suppress event bit in the returned integer.
	 * </P>
	 * @param svc TODO
	 * @param parameters
	 *            The package parameters (timeout, retry, etc...) to be used for
	 *            this poll.
	 * @return The availability of the interface and if a transition event
	 *         should be suppressed.
	 * 
	 * @exception java.lang.RuntimeException
	 *                Thrown if an unrecoverable error occurs that prevents the
	 *                interface from being monitored.
	 * 
	 * @see PollStatus#SERVICE_AVAILABLE
	 * @see PollStatus#SERVICE_UNAVAILABLE
	 */
	public PollStatus poll(MonitoredService svc, Map<String, Object> parameters);
}