From 7817621ad1a62db1bd7b7b60ed823b4da169a34a Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Wed, 7 Jun 2017 11:28:45 +0200
Subject: add metric scaler

---
 .../src/main/scala/kamon/util/MetricScaler.scala   | 58 ++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 kamon-core/src/main/scala/kamon/util/MetricScaler.scala

diff --git a/kamon-core/src/main/scala/kamon/util/MetricScaler.scala b/kamon-core/src/main/scala/kamon/util/MetricScaler.scala
new file mode 100644
index 00000000..ca77a9a1
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/util/MetricScaler.scala
@@ -0,0 +1,58 @@
+package kamon.util
+
+import kamon.metric.{DynamicRange, HdrHistogram, MetricDistribution, MetricValue}
+import kamon.util.MeasurementUnit.Dimension
+
+class MetricScaler(targetTimeUnit: MeasurementUnit, targetInformationUnit: MeasurementUnit, dynamicRange: DynamicRange) {
+  require(targetTimeUnit.dimension == Dimension.Time, "timeUnit must be in the time dimension.")
+  require(targetInformationUnit.dimension == Dimension.Information, "informationUnit must be in the information dimension.")
+
+  val scaleHistogram = new HdrHistogram("scaler", Map.empty, MeasurementUnit.none, dynamicRange)
+
+  def scaleDistribution(metric: MetricDistribution): MetricDistribution = {
+    metric.measurementUnit match {
+      case MeasurementUnit(Dimension.Time, magnitude) if(magnitude != targetTimeUnit.magnitude) =>
+        scaleMetricDistributionToTarget(metric, targetTimeUnit)
+
+      case MeasurementUnit(Dimension.Information, magnitude) if(magnitude != targetTimeUnit.magnitude) =>
+        scaleMetricDistributionToTarget(metric, targetInformationUnit)
+
+      case _ => metric
+    }
+  }
+
+  def scaleMetricValue(metric: MetricValue): MetricValue = {
+    metric.measurementUnit match {
+      case MeasurementUnit(Dimension.Time, magnitude) if(magnitude != targetTimeUnit.magnitude) =>
+        scaleMetricValueToTarget(metric, targetTimeUnit)
+
+      case MeasurementUnit(Dimension.Information, magnitude) if(magnitude != targetTimeUnit.magnitude) =>
+        scaleMetricValueToTarget(metric, targetInformationUnit)
+
+      case _ => metric
+    }
+  }
+
+  private def scaleMetricDistributionToTarget(metric: MetricDistribution, targetUnit: MeasurementUnit): MetricDistribution = {
+    metric.distribution.bucketsIterator.foreach(b => {
+      val scaledValue = MeasurementUnit.scale(b.value, metric.measurementUnit, targetUnit)
+      scaleHistogram.record(Math.ceil(scaledValue).toLong, b.frequency)
+    })
+
+    scaleHistogram.snapshot().copy(
+      name = metric.name,
+      tags = metric.tags,
+      measurementUnit = targetUnit,
+      dynamicRange = dynamicRange
+    )
+  }
+
+  private def scaleMetricValueToTarget(metric: MetricValue, targetUnit: MeasurementUnit): MetricValue = {
+    val scaledValue = MeasurementUnit.scale(metric.value, metric.measurementUnit, targetUnit)
+
+    metric.copy(
+      value = Math.ceil(scaledValue).toLong,
+      measurementUnit = targetUnit
+    )
+  }
+}
-- 
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