! 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, 81 deletions

diff --git a/kamon-core/src/test/scala/kamon/metrics/TickMetricSnapshotBufferSpec.scala b/kamon-core/src/test/scala/kamon/metrics/TickMetricSnapshotBufferSpec.scala
deleted file mode 100644
index d0a0c707..00000000
--- a/kamon-core/src/test/scala/kamon/metrics/TickMetricSnapshotBufferSpec.scala
+++ /dev/null
@@ -1,81 +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, WordSpecLike }
-import akka.testkit.TestKit
-import akka.actor.ActorSystem
-import scala.concurrent.duration._
-import kamon.metrics.Subscriptions.TickMetricSnapshot
-import kamon.metrics.MetricSnapshot.Measurement
-
-class TickMetricSnapshotBufferSpec extends TestKit(ActorSystem("tick-metric-snapshot-buffer")) with WordSpecLike with Matchers {
-
-  "the TickMetricSnapshotBuffer" should {
-    "merge TickMetricSnapshots received until the flush timeout is reached and fix the from/to fields" in new SnapshotFixtures {
-      val buffer = system.actorOf(TickMetricSnapshotBuffer.props(3 seconds, testActor))
-
-      buffer ! firstEmpty
-      buffer ! secondEmpty
-      buffer ! thirdEmpty
-
-      within(2 seconds)(expectNoMsg())
-      val mergedSnapshot = expectMsgType[TickMetricSnapshot]
-
-      mergedSnapshot.from should equal(1000)
-      mergedSnapshot.to should equal(4000)
-      mergedSnapshot.metrics should be('empty)
-    }
-
-    "merge empty and non-empty snapshots" in new SnapshotFixtures {
-      val buffer = system.actorOf(TickMetricSnapshotBuffer.props(3 seconds, testActor))
-
-      buffer ! firstNonEmpty
-      buffer ! secondNonEmpty
-      buffer ! thirdEmpty
-
-      within(2 seconds)(expectNoMsg())
-      val mergedSnapshot = expectMsgType[TickMetricSnapshot]
-
-      mergedSnapshot.from should equal(1000)
-      mergedSnapshot.to should equal(4000)
-      mergedSnapshot.metrics should not be ('empty)
-
-      val testMetricSnapshot = mergedSnapshot.metrics(CustomMetric("test-metric")).metrics(CustomMetric.RecordedValues)
-      testMetricSnapshot.min should equal(1)
-      testMetricSnapshot.max should equal(10)
-      testMetricSnapshot.numberOfMeasurements should equal(35)
-      testMetricSnapshot.measurements should contain allOf (Measurement(1, 10), Measurement(4, 9), Measurement(10, 16))
-
-    }
-  }
-
-  trait SnapshotFixtures {
-    val firstEmpty = TickMetricSnapshot(1000, 2000, Map.empty)
-    val secondEmpty = TickMetricSnapshot(2000, 3000, Map.empty)
-    val thirdEmpty = TickMetricSnapshot(3000, 4000, Map.empty)
-
-    val firstNonEmpty = TickMetricSnapshot(1000, 2000,
-      Map((CustomMetric("test-metric") -> SimpleGroupSnapshot(Map(CustomMetric.RecordedValues -> MetricSnapshot(InstrumentTypes.Histogram, 20, Scale.Unit, Vector(Measurement(1, 10), Measurement(10, 10))))))))
-
-    val secondNonEmpty = TickMetricSnapshot(1000, 2000,
-      Map((CustomMetric("test-metric") -> SimpleGroupSnapshot(Map(CustomMetric.RecordedValues -> MetricSnapshot(InstrumentTypes.Histogram, 15, Scale.Unit, Vector(Measurement(4, 9), Measurement(10, 6))))))))
-
-  }
-
-  case class SimpleGroupSnapshot(metrics: Map[MetricIdentity, MetricSnapshotLike]) extends MetricGroupSnapshot
-}