com.facebook.stats.MultiWindowMax.java Source code

Introduction

Here is the source code for com.facebook.stats.MultiWindowMax.java

Source

/*
 * Copyright (C) 2012 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.stats;

import org.joda.time.DateTime;
import org.joda.time.DateTimeUtils;
import org.joda.time.Duration;
import org.joda.time.ReadableDateTime;
import org.joda.time.ReadableDuration;

public class MultiWindowMax implements ReadableMultiWindowCounter, WritableMultiWindowStat {
    private static final ReadableDuration COUNTER_GRANULARITY = Duration.standardSeconds(6);

    private final Object rollLock = new Object();
    private final CompositeMax allTimeCounter;
    private final CompositeMax hourCounter;
    private final CompositeMax tenMinuteCounter;
    private final CompositeMax minuteCounter;
    private volatile EventCounterIf<EventCounter> currentCounter;

    MultiWindowMax(CompositeMax allTimeCounter, CompositeMax hourCounter, CompositeMax tenMinuteCounter,
            CompositeMax minuteCounter) {
        this.allTimeCounter = allTimeCounter;
        this.hourCounter = hourCounter;
        this.tenMinuteCounter = tenMinuteCounter;
        this.minuteCounter = minuteCounter;
        currentCounter = addNewCurrentCounter();
    }

    public MultiWindowMax() {
        this(new CompositeMax(Duration.standardMinutes(Integer.MAX_VALUE)),
                new CompositeMax(Duration.standardMinutes(60)), new CompositeMax(Duration.standardMinutes(10)),
                new CompositeMax(Duration.standardMinutes(1)));
    }

    @Override
    public void add(long value) {
        rollCurrentIfNeeded();
        currentCounter.add(value);
    }

    @Override
    public long getMinuteValue() {
        rollCurrentIfNeeded();
        return minuteCounter.getValue();
    }

    @Override
    public long getTenMinuteValue() {
        rollCurrentIfNeeded();
        return tenMinuteCounter.getValue();
    }

    @Override
    public long getHourValue() {
        rollCurrentIfNeeded();
        return hourCounter.getValue();
    }

    @Override
    public long getAllTimeValue() {
        rollCurrentIfNeeded();
        return allTimeCounter.getValue();
    }

    private void rollCurrentIfNeeded() {
        //do outside the synchronized block
        long now = DateTimeUtils.currentTimeMillis();
        // this is false for the majority of calls, so skip lock acquisition
        if (currentCounter.getEnd().getMillis() < now) {
            synchronized (rollLock) {
                // lock and re-check
                if (currentCounter.getEnd().getMillis() < now) {
                    currentCounter = addNewCurrentCounter();
                }
            }
        }
    }

    private MaxEventCounter addNewCurrentCounter() {
        ReadableDateTime now = new DateTime();

        MaxEventCounter maxEventCounter = new MaxEventCounter(now, now.toDateTime().plus(COUNTER_GRANULARITY));

        allTimeCounter.addEventCounter(maxEventCounter);
        hourCounter.addEventCounter(maxEventCounter);
        tenMinuteCounter.addEventCounter(maxEventCounter);
        minuteCounter.addEventCounter(maxEventCounter);

        return maxEventCounter;
    }

    public MultiWindowMax merge(MultiWindowMax other) {
        return new MultiWindowMax((CompositeMax) allTimeCounter.merge(other.allTimeCounter),
                (CompositeMax) hourCounter.merge(other.hourCounter),
                (CompositeMax) tenMinuteCounter.merge(other.tenMinuteCounter),
                (CompositeMax) minuteCounter.merge(other.minuteCounter));
    }
}