! 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, 104 deletions

diff --git a/kamon-core/src/main/scala/kamon/metrics/MetricsExtension.scala b/kamon-core/src/main/scala/kamon/metrics/MetricsExtension.scala
deleted file mode 100644
index c60babb2..00000000
--- a/kamon-core/src/main/scala/kamon/metrics/MetricsExtension.scala
+++ /dev/null
@@ -1,104 +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 scala.collection.concurrent.TrieMap
-import akka.actor._
-import com.typesafe.config.Config
-import kamon.util.GlobPathFilter
-import kamon.Kamon
-import akka.actor
-import kamon.metrics.Metrics.MetricGroupFilter
-import kamon.metrics.Subscriptions.Subscribe
-import java.util.concurrent.TimeUnit
-
-class MetricsExtension(system: ExtendedActorSystem) extends Kamon.Extension {
-  val metricsExtConfig = system.settings.config.getConfig("kamon.metrics")
-
-  /** Configured Dispatchers */
-  val metricSubscriptionsDispatcher = system.dispatchers.lookup(metricsExtConfig.getString("dispatchers.metric-subscriptions"))
-  val gaugeRecordingsDispatcher = system.dispatchers.lookup(metricsExtConfig.getString("dispatchers.gauge-recordings"))
-
-  /** Configuration Settings */
-  val gaugeRecordingInterval = metricsExtConfig.getDuration("gauge-recording-interval", TimeUnit.MILLISECONDS)
-
-  val storage = TrieMap[MetricGroupIdentity, MetricGroupRecorder]()
-  val filters = loadFilters(metricsExtConfig)
-  lazy val subscriptions = system.actorOf(Props[Subscriptions], "kamon-metrics-subscriptions")
-
-  def register(identity: MetricGroupIdentity, factory: MetricGroupFactory): Option[factory.GroupRecorder] = {
-    if (shouldTrack(identity))
-      Some(storage.getOrElseUpdate(identity, factory.create(metricsExtConfig)).asInstanceOf[factory.GroupRecorder])
-    else
-      None
-  }
-
-  def unregister(identity: MetricGroupIdentity): Unit = {
-    storage.remove(identity)
-  }
-
-  def subscribe[C <: MetricGroupCategory](category: C, selection: String, receiver: ActorRef, permanently: Boolean = false): Unit = {
-    subscriptions.tell(Subscribe(category, selection, permanently), receiver)
-  }
-
-  def collect: Map[MetricGroupIdentity, MetricGroupSnapshot] = {
-    (for ((identity, recorder) ← storage) yield (identity, recorder.collect)).toMap
-  }
-
-  def scheduleGaugeRecorder(body: ⇒ Unit): Cancellable = {
-    import scala.concurrent.duration._
-
-    system.scheduler.schedule(gaugeRecordingInterval milliseconds, gaugeRecordingInterval milliseconds) {
-      body
-    }(gaugeRecordingsDispatcher)
-  }
-
-  private def shouldTrack(identity: MetricGroupIdentity): Boolean = {
-    filters.get(identity.category.name).map(filter ⇒ filter.accept(identity.name)).getOrElse(false)
-  }
-
-  def loadFilters(config: Config): Map[String, MetricGroupFilter] = {
-    import scala.collection.JavaConverters._
-
-    val filters = config.getObjectList("filters").asScala
-
-    val allFilters =
-      for (
-        filter ← filters;
-        entry ← filter.entrySet().asScala
-      ) yield {
-        val key = entry.getKey
-        val keyBasedConfig = entry.getValue.atKey(key)
-
-        val includes = keyBasedConfig.getStringList(s"$key.includes").asScala.map(inc ⇒ new GlobPathFilter(inc)).toList
-        val excludes = keyBasedConfig.getStringList(s"$key.excludes").asScala.map(exc ⇒ new GlobPathFilter(exc)).toList
-
-        (key, MetricGroupFilter(includes, excludes))
-      }
-
-    allFilters.toMap
-  }
-}
-
-object Metrics extends ExtensionId[MetricsExtension] with ExtensionIdProvider {
-  def lookup(): ExtensionId[_ <: actor.Extension] = Metrics
-  def createExtension(system: ExtendedActorSystem): MetricsExtension = new MetricsExtension(system)
-
-  case class MetricGroupFilter(includes: List[GlobPathFilter], excludes: List[GlobPathFilter]) {
-    def accept(name: String): Boolean = includes.exists(_.accept(name)) && !excludes.exists(_.accept(name))
-  }
-}