! 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, 72 deletions

diff --git a/kamon-core/src/test/scala/kamon/metrics/MetricSnapshotSpec.scala b/kamon-core/src/test/scala/kamon/metrics/MetricSnapshotSpec.scala
deleted file mode 100644
index 4d6ebc49..00000000
--- a/kamon-core/src/test/scala/kamon/metrics/MetricSnapshotSpec.scala
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * =========================================================================================
- * 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
-
-import org.scalatest.{ Matchers, WordSpec }
-import kamon.metrics.MetricSnapshot.Measurement
-
-class MetricSnapshotSpec extends WordSpec with Matchers {
-
-  "a metric snapshot" should {
-    "support a max operation" in new SnapshotFixtures {
-      snapshotA.max should be(17)
-      snapshotB.max should be(10)
-      snapshotC.max should be(1)
-    }
-
-    "support a min operation" in new SnapshotFixtures {
-      snapshotA.min should be(1)
-      snapshotB.min should be(2)
-      snapshotC.min should be(1)
-    }
-
-    "be able to merge with other snapshot" in new SnapshotFixtures {
-      val merged = snapshotA.merge(snapshotB).merge(snapshotC)
-
-      merged.min should be(1)
-      merged.max should be(17)
-      merged.numberOfMeasurements should be(300)
-      merged.measurements.map(_.value) should contain inOrderOnly (1, 2, 4, 5, 7, 10, 17)
-    }
-
-    "be able to merge with empty snapshots" in new SnapshotFixtures {
-      snapshotA.merge(emptySnapshot) should be(snapshotA)
-      emptySnapshot.merge(snapshotA).merge(emptySnapshot) should be(snapshotA)
-      snapshotC.merge(emptySnapshot) should be(snapshotC)
-    }
-
-  }
-
-  trait SnapshotFixtures {
-    val emptySnapshot = MetricSnapshot(InstrumentTypes.Histogram, 0, Scale.Unit, Vector.empty)
-
-    val snapshotA = MetricSnapshot(InstrumentTypes.Histogram, 100, Scale.Unit, Vector(
-      Measurement(1, 3),
-      Measurement(2, 15),
-      Measurement(5, 68),
-      Measurement(7, 13),
-      Measurement(17, 1)))
-
-    val snapshotB = MetricSnapshot(InstrumentTypes.Histogram, 100, Scale.Unit, Vector(
-      Measurement(2, 6),
-      Measurement(4, 48),
-      Measurement(5, 39),
-      Measurement(10, 7)))
-
-    val snapshotC = MetricSnapshot(InstrumentTypes.Counter, 100, Scale.Unit, Vector(Measurement(1, 100)))
-  }
-}