MonitoringView.java

package io.pcp.parfait;

import java.util.Collection;

/**
 * An output bridge for a particular set of Monitorables. A MonitoringView
 * provides a convenient lifecycle for an output destination to know when all
 * metrics have been set up and initialized, and are ready to be output to the
 * destination. When {@link #startMonitoring(java.util.Collection)} is called, all Monitorables should be
 * initialized and ready to be written to the output. {@link #stopMonitoring(java.util.Collection)} should be
 * (but, of course, is not guaranteed to be) called when the monitoring
 * subsystem is being shut down.
 */
public interface MonitoringView {

    /**
     * Instructs the view to begin its work using the set of Monitorable instances
     * as the basis for whatever it is this 'view' wants to do with it (say, start externalising
     * the state of the metrics to an external file).
     *
     * It is expected that this view tracks its own start/stop state, and that clients
     * of this implementation should correctly call {@link #stopMonitoring(java.util.Collection)}  before recalling startMonitoring.
     *
     * @param monitorables the Collection of metrics to start monitoring
     */
    void startMonitoring(Collection<Monitorable<?>> monitorables);

    /**
     * Stops monitoring updates on the Monitorables in the provided registry, any
     * updates to any of the monitorables passed in will no longer be tracked by this View
     *
     * @param monitorables the Collection of metrics to stop monitoring
     */
    void stopMonitoring(Collection<Monitorable<?>> monitorables);

    /**
     * @return whether or not this view has been started with {@link #startMonitoring(java.util.Collection)} ()}
     */
    boolean isRunning();
}