! 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, 3 insertions, 9 deletions

diff --git a/kamon-spray/src/main/scala/spray/can/client/ClientRequestInstrumentation.scala b/kamon-spray/src/main/scala/spray/can/client/ClientRequestInstrumentation.scala
index d7d9cf09..d787bda4 100644
--- a/kamon-spray/src/main/scala/spray/can/client/ClientRequestInstrumentation.scala
+++ b/kamon-spray/src/main/scala/spray/can/client/ClientRequestInstrumentation.scala
@@ -21,7 +21,7 @@ import org.aspectj.lang.ProceedingJoinPoint
 import spray.http.{ HttpHeader, HttpResponse, HttpMessageEnd, HttpRequest }
 import spray.http.HttpHeaders.{ RawHeader, Host }
 import kamon.trace.{ TraceRecorder, SegmentCompletionHandleAware }
-import kamon.metrics.TraceMetrics.HttpClientRequest
+import kamon.metric.TraceMetrics.HttpClientRequest
 import kamon.Kamon
 import kamon.spray.{ ClientSegmentCollectionStrategy, Spray }
 import akka.actor.ActorRef
@@ -30,7 +30,6 @@ import akka.util.Timeout
 
 @Aspect
 class ClientRequestInstrumentation {
-  import ClientRequestInstrumentation._
 
   @DeclareMixin("spray.can.client.HttpHostConnector.RequestContext")
   def mixin: SegmentCompletionHandleAware = SegmentCompletionHandleAware.default
@@ -51,7 +50,7 @@ class ClientRequestInstrumentation {
         if (sprayExtension.clientSegmentCollectionStrategy == ClientSegmentCollectionStrategy.Internal) {
           val requestAttributes = basicRequestAttributes(request)
           val clientRequestName = sprayExtension.assignHttpClientRequestName(request)
-          val completionHandle = traceContext.startSegment(HttpClientRequest(clientRequestName, SprayTime), requestAttributes)
+          val completionHandle = traceContext.startSegment(HttpClientRequest(clientRequestName), requestAttributes)
 
           ctx.segmentCompletionHandle = Some(completionHandle)
         }
@@ -102,7 +101,7 @@ class ClientRequestInstrumentation {
         if (sprayExtension.clientSegmentCollectionStrategy == ClientSegmentCollectionStrategy.Pipelining) {
           val requestAttributes = basicRequestAttributes(request)
           val clientRequestName = sprayExtension.assignHttpClientRequestName(request)
-          val completionHandle = traceContext.startSegment(HttpClientRequest(clientRequestName, UserTime), requestAttributes)
+          val completionHandle = traceContext.startSegment(HttpClientRequest(clientRequestName), requestAttributes)
 
           responseFuture.onComplete { result ⇒
             completionHandle.finish(Map.empty)
@@ -139,8 +138,3 @@ class ClientRequestInstrumentation {
     pjp.proceed(Array(modifiedHeaders))
   }
 }
-
-object ClientRequestInstrumentation {
-  val SprayTime = "SprayTime"
-  val UserTime = "UserTime"
-}