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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 kamon.metrics.instruments
import org.HdrHistogram.HdrRecorder
import kamon.metrics.{ Scale, MetricSnapshotLike }
/**
* This recorder keeps track of the last value recoded and automatically adds it after collecting a snapshot. This is
* useful in cases where the absence of recordings does not necessarily mean the absence of values. For example, if this
* recorder is used for recording the mailbox size of an actor, and it only gets updated upon message enqueue o dequeue,
* the absence of recordings during 1 second means that the size hasn't change (example: the actor being blocked doing
* some work) and it should keep its last known value, instead of dropping to zero and then going back to the real value
* after a new event is processed.
*
*/
class ContinuousHdrRecorder(highestTrackableValue: Long, significantValueDigits: Int, scale: Scale)
extends HdrRecorder(highestTrackableValue, significantValueDigits, scale) {
@volatile private var lastRecordedValue: Long = 0
override def record(value: Long): Unit = {
lastRecordedValue = value
super.record(value)
}
override def collect(): MetricSnapshotLike = {
val snapshot = super.collect()
super.record(lastRecordedValue)
snapshot
}
}
object ContinuousHdrRecorder {
def apply(highestTrackableValue: Long, significantValueDigits: Int, scale: Scale) =
new ContinuousHdrRecorder(highestTrackableValue, significantValueDigits, scale)
}
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