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/*
* =========================================================================================
* Copyright © 2013 the kamon project <http://kamon.io/>
*
* 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 org.HdrHistogram
import java.util.concurrent.atomic.AtomicLongFieldUpdater
import scala.annotation.tailrec
import kamon.metrics._
/**
* This implementation aims to be used for real time data collection where data snapshots are taken often over time.
* The snapshotAndReset() operation extracts all the recorded values from the histogram and resets the counts, but still
* leave it in a consistent state even in the case of concurrent modification while the snapshot is being taken.
*/
class HdrRecorder(highestTrackableValue: Long, significantValueDigits: Int, scale: Scale)
extends AtomicHistogram(1L, highestTrackableValue, significantValueDigits) with MetricRecorder {
import HdrRecorder.totalCountUpdater
def record(value: Long): Unit = recordValue(value)
def collect(): MetricSnapshotLike = {
val entries = Vector.newBuilder[MetricSnapshot.Measurement]
val countsLength = counts.length()
@tailrec def iterate(index: Int, previousValue: Long, nrOfRecordings: Long, bucketLimit: Long, increment: Long): Long = {
if (index < countsLength) {
val currentValue = previousValue + increment
val countAtValue = counts.getAndSet(index, 0)
if (countAtValue > 0)
entries += MetricSnapshot.Measurement(currentValue, countAtValue)
if (currentValue == bucketLimit)
iterate(index + 1, currentValue, nrOfRecordings + countAtValue, (bucketLimit << 1) + 1, increment << 1)
else
iterate(index + 1, currentValue, nrOfRecordings + countAtValue, bucketLimit, increment)
} else {
nrOfRecordings
}
}
val nrOfRecordings = iterate(0, -1, 0, subBucketMask, 1)
def tryUpdateTotalCount: Boolean = {
val previousTotalCount = getTotalCount
val newTotalCount = previousTotalCount - nrOfRecordings
totalCountUpdater.compareAndSet(this, previousTotalCount, newTotalCount)
}
while (!tryUpdateTotalCount) {}
MetricSnapshot(InstrumentTypes.Histogram, nrOfRecordings, scale, entries.result())
}
}
object HdrRecorder {
val totalCountUpdater = AtomicLongFieldUpdater.newUpdater(classOf[AtomicHistogram], "totalCount")
def apply(highestTrackableValue: Long, significantValueDigits: Int, scale: Scale): HdrRecorder =
new HdrRecorder(highestTrackableValue, significantValueDigits, scale)
}
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