/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.controller.cluster.common.actor;

import akka.actor.AbstractActor;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Timer;
import org.opendaylight.controller.cluster.reporting.MetricsReporter;
import scala.PartialFunction;
import scala.runtime.AbstractPartialFunction;
import scala.runtime.BoxedUnit;

/**
 * Represents behaviour that can be exhibited by actors of type {@link AbstractActor}
 *
 * <p>
 * This behaviour meters actor's default behaviour. It captures 2 metrics:
 * <ul>
 *     <li>message processing rate of actor's receive block</li>
 *     <li>message processing rate by message type</li>
 * </ul>
 * The information is reported to {@link org.opendaylight.controller.cluster.reporting.MetricsReporter}
 */
public class MeteringBehavior extends AbstractPartialFunction<Object, BoxedUnit> {
    public static final String DOMAIN = "org.opendaylight.controller.actor.metric";

    private static final String MSG_PROCESSING_RATE = "msg-rate";

    private final MetricRegistry metricRegistry = MetricsReporter.getInstance(DOMAIN).getMetricsRegistry();
    private final String actorQualifiedName;
    private final Timer msgProcessingTimer;
    private final PartialFunction<Object, BoxedUnit> receive;

    private MeteringBehavior(final String actorName, final AbstractActor meteredActor) {
        actorQualifiedName = meteredActor.getSelf().path().parent().toStringWithoutAddress() + "/" + actorName;
        msgProcessingTimer = metricRegistry.timer(MetricRegistry.name(actorQualifiedName, MSG_PROCESSING_RATE));
        receive = meteredActor.createReceive().onMessage();
    }

    /**
     * Constructs an instance.
     *
     * @param actor whose behaviour needs to be metered
     */
    public MeteringBehavior(final AbstractUntypedActorWithMetering actor) {
        this(actor.getActorNameOverride() != null ? actor.getActorNameOverride() : actor.getSelf().path().name(),
                actor);
    }

    public MeteringBehavior(final AbstractActor actor) {
        this(actor.getSelf().path().name(), actor);
    }

    @Override
    public boolean isDefinedAt(final Object obj) {
        return receive.isDefinedAt(obj);
    }

    /**
     * Uses 2 timers to measure message processing rate. One for overall message processing rate and
     * another to measure rate by message type. The timers are re-used if they were previously created.
     *
     * <p>
     * {@link com.codahale.metrics.MetricRegistry} maintains a reservoir for different timers where
     * collected timings are kept. It exposes various metrics for each timer based on collected
     * data. Eg: count of messages, 99, 95, 50... percentiles, max, mean etc.
     *
     * <p>
     * These metrics are exposed as JMX bean.
     *
     * @see <a href="http://dropwizard.github.io/metrics/manual/core/#timers">
     *     http://dropwizard.github.io/metrics/manual/core/#timers</a>
     *
     * @param message the message to process
     */
    @Override
    public BoxedUnit apply(final Object message) {
        final String messageType = message.getClass().getSimpleName();
        final String msgProcessingTimeByMsgType =
                MetricRegistry.name(actorQualifiedName, MSG_PROCESSING_RATE, messageType);
        final Timer msgProcessingTimerByMsgType = metricRegistry.timer(msgProcessingTimeByMsgType);

        //start timers
        final Timer.Context context = msgProcessingTimer.time();
        final Timer.Context contextByMsgType = msgProcessingTimerByMsgType.time();

        try {
            return receive.apply(message);
        } finally {
            //stop timers
            contextByMsgType.stop();
            context.stop();
        }
    }
}