content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.alibaba.metrics;
  
  import java.util.Map;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * A meter metric which measures mean throughput and one-, five-, and fifteen-minute
   * exponentially-weighted moving average throughputs.
   *
   * @see EWMA
   */
  public class MeterImpl implements Meter {
  
      private static final long TICK_INTERVAL = TimeUnit.SECONDS.toNanos(5);
      private static final int DEFAULT_NUM_OF_BUCKET =
              Integer.getInteger("com.alibaba.metrics.numberOfBucket", 10);
  
      private final EWMA m1Rate = EWMA.oneMinuteEWMA();
      private final EWMA m5Rate = EWMA.fiveMinuteEWMA();
      private final EWMA m15Rate = EWMA.fifteenMinuteEWMA();
  
      private final long startTime;
      private final AtomicLong lastTick;
      private final Clock clock;
  
      private final BucketCounterImpl bucketCounter;
  
      private final LongAdder uncounted = new LongAdder();
  
      /**
       * Creates a new {@link Meter}.
       */
      public MeterImpl() {
          this(Clock.defaultClock(), DEFAULT_NUM_OF_BUCKET, 60);
      }
  
      /**
       * Creates a new {@link Meter} with given bucket interval
       */
      public MeterImpl(int interval) {
          this(Clock.defaultClock(), DEFAULT_NUM_OF_BUCKET, interval);
      }
  
      public MeterImpl(Clock clock) {
          this(clock, DEFAULT_NUM_OF_BUCKET, 60);
      }
  
      public MeterImpl(Clock clock, int interval) {
          this(clock, DEFAULT_NUM_OF_BUCKET, interval);
      }
  
      /**
       * Creates a new {@link Meter}.
       *
       * @param clock          the clock to use for the meter ticks
       * @param numberOfBucket the number of bucket to store
       * @param interval       the time interval for each bucket
       */
      public MeterImpl(Clock clock, int numberOfBucket, int interval) {
          this.clock = clock;
          this.startTime = this.clock.getTick();
          this.lastTick = new AtomicLong(startTime);
          this.bucketCounter = new BucketCounterImpl(interval, numberOfBucket, clock);
      }
  
      /**
       * Mark the occurrence of an event.
       */
      public void mark() {
          mark(1);
      }
  
      /**
       * Mark the occurrence of a given number of events.
       *
       * @param n the number of events
       */
      public void mark(long n) {
          tickIfNecessary();
          uncounted.add(n);
          bucketCounter.update(n);
      }
  
      private void tickIfNecessary() {
          final long oldTick = lastTick.get();
          final long newTick = clock.getTick();
          final long age = newTick - oldTick;
          if (age > TICK_INTERVAL) {
              final long newIntervalStartTick = newTick - age % TICK_INTERVAL;
              if (lastTick.compareAndSet(oldTick, newIntervalStartTick)) {
                  final long requiredTicks = age / TICK_INTERVAL;
                  for (long i = 0; i < requiredTicks; i++) {
                      final long count = uncounted.sumThenReset();
                      m1Rate.tick(count);
                      m5Rate.tick(count);
                      m15Rate.tick(count);
                  }
              }
          }
      }
  
      public long getCount() {
          return bucketCounter.getCount();
      }
  
      @Override
      public Map<Long, Long> getInstantCount() {
          return bucketCounter.getBucketCounts();
      }
  
      @Override
      public Map<Long, Long> getInstantCount(long startTime) {
          return bucketCounter.getBucketCounts(startTime);
      }
  
      @Override
      public int getInstantCountInterval() {
          return bucketCounter.getBucketInterval();
      }
  
      public double getFifteenMinuteRate() {
          tickIfNecessary();
          return m15Rate.getRate(TimeUnit.SECONDS);
      }
  
      public double getFiveMinuteRate() {
          tickIfNecessary();
          return m5Rate.getRate(TimeUnit.SECONDS);
      }
  
      public double getMeanRate() {
          if (getCount() == 0) {
              return 0.0;
          } else {
              final double elapsed = (clock.getTick() - startTime);
              return getCount() / elapsed * TimeUnit.SECONDS.toNanos(1);
          }
      }
  
      public double getOneMinuteRate() {
          tickIfNecessary();
          return m1Rate.getRate(TimeUnit.SECONDS);
      }
  
      @Override
      public long lastUpdateTime() {
          return bucketCounter.lastUpdateTime();
      }
  }
  