! core: Avoid updating the totalCount on our histograms and close #293

2 files changed, 16 insertions, 37 deletions

diff --git a/kamon-core/src/main/scala/kamon/metric/instrument/Histogram.scala b/kamon-core/src/main/scala/kamon/metric/instrument/Histogram.scala
index 5c4c7f71..d2fb88a2 100644
--- a/kamon-core/src/main/scala/kamon/metric/instrument/Histogram.scala
+++ b/kamon-core/src/main/scala/kamon/metric/instrument/Histogram.scala
@@ -17,9 +17,9 @@
 package kamon.metric.instrument
 
 import java.nio.LongBuffer
-import org.HdrHistogram.AtomicHistogramFieldsAccessor
-import kamon.metric.instrument.Histogram.{ Snapshot, DynamicRange }
-import org.HdrHistogram.AtomicHistogram
+
+import kamon.metric.instrument.Histogram.{ DynamicRange, Snapshot }
+import org.HdrHistogram.ModifiedAtomicHistogram
 
 trait Histogram extends Instrument {
   type SnapshotType = Histogram.Snapshot
@@ -54,11 +54,9 @@ object Histogram {
    * @param lowestDiscernibleValue
    *    The lowest value that can be discerned (distinguished from 0) by the histogram.Must be a positive integer that
    *    is >= 1. May be internally rounded down to nearest power of 2.
-   *
    * @param highestTrackableValue
    *    The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue).
    *    Must not be larger than (Long.MAX_VALUE/2).
-   *
    * @param precision
    *    The number of significant decimal digits to which the histogram will maintain value resolution and separation.
    *    Must be a non-negative integer between 1 and 3.
@@ -108,9 +106,8 @@ object Histogram {
  *  The collect(..) 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 HdrHistogram(dynamicRange: DynamicRange) extends AtomicHistogram(dynamicRange.lowestDiscernibleValue,
-  dynamicRange.highestTrackableValue, dynamicRange.precision) with Histogram with AtomicHistogramFieldsAccessor {
-  import AtomicHistogramFieldsAccessor.totalCountUpdater
+class HdrHistogram(dynamicRange: DynamicRange) extends ModifiedAtomicHistogram(dynamicRange.lowestDiscernibleValue,
+  dynamicRange.highestTrackableValue, dynamicRange.precision) with Histogram {
 
   def record(value: Long): Unit = recordValue(value)
 
@@ -125,7 +122,7 @@ class HdrHistogram(dynamicRange: DynamicRange) extends AtomicHistogram(dynamicRa
 
     val measurementsArray = Array.ofDim[Long](buffer.limit())
     buffer.get(measurementsArray, 0, measurementsArray.length)
-    new CompactHdrSnapshot(nrOfMeasurements, measurementsArray, unitMagnitude(), subBucketHalfCount(), subBucketHalfCountMagnitude())
+    new CompactHdrSnapshot(nrOfMeasurements, measurementsArray, protectedUnitMagnitude(), protectedSubBucketHalfCount(), protectedSubBucketHalfCountMagnitude())
   }
 
   def getCounts = countsArray().length()
@@ -148,22 +145,8 @@ class HdrHistogram(dynamicRange: DynamicRange) extends AtomicHistogram(dynamicRa
 
       index += 1
     }
-
-    reestablishTotalCount(nrOfMeasurements)
     nrOfMeasurements
   }
-
-  private def reestablishTotalCount(diff: Long): Unit = {
-    def tryUpdateTotalCount: Boolean = {
-      val previousTotalCount = totalCountUpdater.get(this)
-      val newTotalCount = previousTotalCount - diff
-
-      totalCountUpdater.compareAndSet(this, previousTotalCount, newTotalCount)
-    }
-
-    while (!tryUpdateTotalCount) {}
-  }
-
 }
 
 case class CompactHdrSnapshot(val numberOfMeasurements: Long, compactRecords: Array[Long], unitMagnitude: Int,
diff --git a/kamon-core/src/main/scala/kamon/metric/instrument/AtomicHistogramFieldsAccessor.scala b/kamon-core/src/main/scala/kamon/metric/instrument/ModifiedAtomicHistogram.scala
index e79090a8..eb01d114 100644
--- a/kamon-core/src/main/scala/kamon/metric/instrument/AtomicHistogramFieldsAccessor.scala
+++ b/kamon-core/src/main/scala/kamon/metric/instrument/ModifiedAtomicHistogram.scala
@@ -16,20 +16,16 @@
 
 package org.HdrHistogram
 
-import java.util.concurrent.atomic.{ AtomicLongArray, AtomicLongFieldUpdater }
+import java.util.concurrent.atomic.AtomicLongArray
 
-trait AtomicHistogramFieldsAccessor {
-  self: AtomicHistogram ⇒
+abstract class ModifiedAtomicHistogram(low: Long, high: Long, precision: Int)
+    extends AtomicHistogram(low, high, precision) { self ⇒
 
-  def countsArray(): AtomicLongArray = self.counts
+  override def incrementTotalCount(): Unit = {}
+  override def addToTotalCount(value: Long): Unit = {}
 
-  def unitMagnitude(): Int = self.unitMagnitude
-
-  def subBucketHalfCount(): Int = self.subBucketHalfCount
-
-  def subBucketHalfCountMagnitude(): Int = self.subBucketHalfCountMagnitude
-}
-
-object AtomicHistogramFieldsAccessor {
-  def totalCountUpdater(): AtomicLongFieldUpdater[AtomicHistogram] = AtomicHistogram.totalCountUpdater
-}
+  def countsArray(): AtomicLongArray = counts
+  def protectedUnitMagnitude(): Int = unitMagnitude
+  def protectedSubBucketHalfCount(): Int = subBucketHalfCount
+  def protectedSubBucketHalfCountMagnitude(): Int = subBucketHalfCountMagnitude
+}
\ No newline at end of file