! all: refactor the core metric recording instruments and accomodate UserMetrics

This PR is including several changes to the kamon-core, most notably:
  - Formalize the interface for Histograms, Counters and MinMaxCounters. Making sure
    that the interfaces are as clean as possible.
  - Move away from the all Vector[Measurement] based Histogram snapshot to a new approach
    in which we use a single long to store both the index in the counts array and the
    frequency on that bucket. The leftmost 2 bytes of each long are used for storing the
    counts array index and the remaining 6 bytes are used for the actual count, and
    everything is put into a simple long array. This way only the buckets that actually
    have values will be included in the snapshot with the smallest possible memory
    footprint.
  - Introduce Gauges.
  - Reorganize the instrumentation for Akka and Scala and rewrite most of the tests
    of this components to avoid going through the subscription protocol to test.
  - Introduce trace tests and fixes on various tests.
  - Necessary changes on new relic, datadog and statsd modules to compile with the new
    codebase.

Pending:
  - Finish the upgrade of the new relic to the current model.
  - Introduce proper limit checks for histograms to ensure that we never pass the 2/6 bytes
    limits.
  - More testing, more testing, more testing.
  - Create the KamonStandalone module.

1 files changed, 0 insertions, 58 deletions

diff --git a/kamon-core/src/main/scala/kamon/metrics/instruments/MinMaxCounter.scala b/kamon-core/src/main/scala/kamon/metrics/instruments/MinMaxCounter.scala
deleted file mode 100644
index ba2550af..00000000
--- a/kamon-core/src/main/scala/kamon/metrics/instruments/MinMaxCounter.scala
+++ /dev/null
@@ -1,58 +0,0 @@
-package kamon.metrics.instruments
-
-/*
- * =========================================================================================
- * Copyright © 2013-2014 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.
- * =========================================================================================
- */
-
-import java.lang.Math._
-import jsr166e.LongMaxUpdater
-import kamon.util.PaddedAtomicLong
-import kamon.metrics.instruments.MinMaxCounter.CounterMeasurement
-
-class MinMaxCounter {
-  private val min = new LongMaxUpdater
-  private val max = new LongMaxUpdater
-  private val sum = new PaddedAtomicLong
-
-  min.update(0L)
-  max.update(0L)
-
-  def increment(value: Long = 1L): Unit = {
-    val currentValue = sum.addAndGet(value)
-    max.update(currentValue)
-  }
-
-  def decrement(value: Long = 1L): Unit = {
-    val currentValue = sum.addAndGet(-value)
-    min.update(-currentValue)
-  }
-
-  def collect(): CounterMeasurement = {
-    val currentValue = {
-      val value = sum.get()
-      if (value < 0) 0 else value
-    }
-    val result = CounterMeasurement(abs(min.maxThenReset()), max.maxThenReset(), currentValue)
-    max.update(currentValue)
-    min.update(-currentValue)
-    result
-  }
-}
-
-object MinMaxCounter {
-  def apply() = new MinMaxCounter()
-
-  case class CounterMeasurement(min: Long, max: Long, current: Long)
-}