! 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, 62 deletions

diff --git a/kamon-core/src/test/scala/kamon/trace/instrumentation/FutureTracingSpec.scala b/kamon-core/src/test/scala/kamon/trace/instrumentation/FutureTracingSpec.scala
deleted file mode 100644
index b1765fd8..00000000
--- a/kamon-core/src/test/scala/kamon/trace/instrumentation/FutureTracingSpec.scala
+++ /dev/null
@@ -1,62 +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.trace.instrumentation
-
-import scala.concurrent.{ ExecutionContext, Future }
-import org.scalatest.{ Matchers, OptionValues, WordSpecLike }
-import org.scalatest.concurrent.{ ScalaFutures, PatienceConfiguration }
-import kamon.trace.TraceRecorder
-import akka.testkit.TestKit
-import akka.actor.ActorSystem
-
-class FutureTracingSpec extends TestKit(ActorSystem("actor-message-passing-tracing-spec")) with WordSpecLike with Matchers
-    with ScalaFutures with PatienceConfiguration with OptionValues {
-
-  implicit val execContext = system.dispatcher
-
-  "a Future created with FutureTracing" should {
-    "capture the TraceContext available when created" which {
-      "must be available when executing the future's body" in {
-
-        val (future, testTraceContext) = TraceRecorder.withNewTraceContext("future-body") {
-          val future = Future(TraceRecorder.currentContext)
-
-          (future, TraceRecorder.currentContext)
-        }
-
-        whenReady(future)(ctxInFuture ⇒
-          ctxInFuture should equal(testTraceContext))
-      }
-
-      "must be available when executing callbacks on the future" in {
-
-        val (future, testTraceContext) = TraceRecorder.withNewTraceContext("future-body") {
-          val future = Future("Hello Kamon!")
-            // The TraceContext is expected to be available during all intermediate processing.
-            .map(_.length)
-            .flatMap(len ⇒ Future(len.toString))
-            .map(s ⇒ TraceRecorder.currentContext)
-
-          (future, TraceRecorder.currentContext)
-        }
-
-        whenReady(future)(ctxInFuture ⇒
-          ctxInFuture should equal(testTraceContext))
-      }
-    }
-  }
-}
-