From 07fc83bb01c5873b47aff50d6d3abbb9f11842bd Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Thu, 12 Feb 2015 11:30:06 +0100
Subject: ! all: Kamon now works as a single instance in a companion object.

---
 kamon-core/src/main/scala/kamon/Kamon.scala        | 76 ++++++++++-------
 .../main/scala/kamon/metric/MetricsExtension.scala | 61 +++++++------
 .../kamon/metric/MetricsExtensionSettings.scala    | 35 ++++----
 .../kamon/metric/SubscriptionsDispatcher.scala     |  9 +-
 .../kamon/metric/TickMetricSnapshotBuffer.scala    |  2 +-
 .../src/main/scala/kamon/metric/UserMetrics.scala  | 33 +++-----
 .../scala/kamon/metric/instrument/Instrument.scala | 19 -----
 .../kamon/metric/instrument/RefreshScheduler.scala | 99 ++++++++++++++++++++++
 .../scala/kamon/trace/MetricsOnlyContext.scala     |  6 +-
 .../src/main/scala/kamon/trace/TraceContext.scala  | 11 +--
 .../main/scala/kamon/trace/TracerExtension.scala   | 62 +++++++++-----
 .../kamon/trace/TracerExtensionSettings.scala      |  6 +-
 .../main/scala/kamon/trace/TracingContext.scala    |  5 +-
 .../src/main/scala/kamon/util/LazyActorRef.scala   | 53 ++++++++++++
 .../kamon/metric/SubscriptionsProtocolSpec.scala   |  3 +-
 .../metric/TickMetricSnapshotBufferSpec.scala      |  5 +-
 .../test/scala/kamon/metric/UserMetricsSpec.scala  | 63 +++++++-------
 .../scala/kamon/metric/instrument/GaugeSpec.scala  |  7 +-
 .../metric/instrument/MinMaxCounterSpec.scala      |  3 +-
 .../test/scala/kamon/testkit/BaseKamonSpec.scala   | 28 ++++--
 .../test/scala/kamon/trace/SimpleTraceSpec.scala   |  8 +-
 21 files changed, 379 insertions(+), 215 deletions(-)
 create mode 100644 kamon-core/src/main/scala/kamon/metric/instrument/RefreshScheduler.scala
 create mode 100644 kamon-core/src/main/scala/kamon/util/LazyActorRef.scala

(limited to 'kamon-core')

diff --git a/kamon-core/src/main/scala/kamon/Kamon.scala b/kamon-core/src/main/scala/kamon/Kamon.scala
index 6fedc065..2bed4737 100644
--- a/kamon-core/src/main/scala/kamon/Kamon.scala
+++ b/kamon-core/src/main/scala/kamon/Kamon.scala
@@ -16,49 +16,61 @@ package kamon
 
 import _root_.akka.actor
 import _root_.akka.actor._
-import com.typesafe.config.Config
+import com.typesafe.config.{ ConfigFactory, Config }
 import kamon.metric._
-import kamon.supervisor.ModuleSupervisor
-import kamon.trace.{ Tracer, TracerExtension }
+import kamon.trace.{ TracerExtensionImpl, TracerExtension }
 
-class Kamon(val actorSystem: ActorSystem) {
-  val metrics: MetricsExtension = Metrics.get(actorSystem)
-  val tracer: TracerExtension = Tracer.get(actorSystem)
-  val userMetrics: UserMetricsExtension = UserMetrics.get(actorSystem)
+object Kamon {
+  trait Extension extends actor.Extension
 
-  // This will cause all auto-start modules to initiate.
-  ModuleSupervisor.get(actorSystem)
+  private case class KamonCoreComponents(
+    metrics: MetricsExtension,
+    tracer: TracerExtension,
+    userMetrics: UserMetricsExtension)
 
-  def shutdown(): Unit =
-    actorSystem.shutdown()
-}
+  @volatile private var _system: ActorSystem = _
+  @volatile private var _coreComponents: Option[KamonCoreComponents] = None
 
-object Kamon {
-  trait Extension extends actor.Extension
-  def apply[T <: Extension](key: ExtensionId[T])(implicit system: ActorSystem): T = key(system)
+  def start(config: Config): Unit = synchronized {
+    if (_coreComponents.isEmpty) {
+      val metrics = MetricsExtensionImpl(config)
+      val simpleMetrics = UserMetricsExtensionImpl(metrics)
+      val tracer = TracerExtensionImpl(metrics, config)
 
-  def apply(): Kamon =
-    apply("kamon")
+      _coreComponents = Some(KamonCoreComponents(metrics, tracer, simpleMetrics))
+      _system = ActorSystem("kamon", config)
 
-  def apply(actorSystemName: String): Kamon =
-    apply(ActorSystem(actorSystemName))
+      metrics.start(_system)
+      tracer.start(_system)
 
-  def apply(actorSystemName: String, config: Config): Kamon =
-    apply(ActorSystem(actorSystemName, config))
+    } else sys.error("Kamon has already been started.")
+  }
 
-  def apply(system: ActorSystem): Kamon =
-    new Kamon(system)
+  def start(): Unit =
+    start(ConfigFactory.load)
 
-  def create(): Kamon =
-    apply()
+  def metrics: MetricsExtension =
+    ifStarted(_.metrics)
 
-  def create(actorSystemName: String): Kamon =
-    apply(ActorSystem(actorSystemName))
+  def tracer: TracerExtension =
+    ifStarted(_.tracer)
 
-  def create(actorSystemName: String, config: Config): Kamon =
-    apply(ActorSystem(actorSystemName, config))
+  def userMetrics: UserMetricsExtension =
+    ifStarted(_.userMetrics)
 
-  def create(system: ActorSystem): Kamon =
-    new Kamon(system)
+  def apply[T <: Kamon.Extension](key: ExtensionId[T]): T =
+    ifStarted { _ ⇒
+      if (_system ne null)
+        key(_system)
+      else
+        sys.error("Cannot retrieve extensions while Kamon is being initialized.")
+    }
+
+  def extension[T <: Kamon.Extension](key: ExtensionId[T]): T =
+    apply(key)
+
+  private def ifStarted[T](thunk: KamonCoreComponents ⇒ T): T =
+    _coreComponents.map(thunk(_)) getOrElse (sys.error("Kamon has not been started yet."))
+
+}
 
-}
\ No newline at end of file
diff --git a/kamon-core/src/main/scala/kamon/metric/MetricsExtension.scala b/kamon-core/src/main/scala/kamon/metric/MetricsExtension.scala
index 88352e21..87911352 100644
--- a/kamon-core/src/main/scala/kamon/metric/MetricsExtension.scala
+++ b/kamon-core/src/main/scala/kamon/metric/MetricsExtension.scala
@@ -16,25 +16,17 @@
 
 package kamon.metric
 
-import akka.actor
+import com.typesafe.config.Config
 import kamon.metric.SubscriptionsDispatcher.{ Unsubscribe, Subscribe }
-import kamon.Kamon
-import kamon.metric.instrument.{ InstrumentFactory, CollectionContext }
-import kamon.supervisor.ModuleSupervisor
+import kamon.metric.instrument.{ DefaultRefreshScheduler, InstrumentFactory, CollectionContext }
 
 import scala.collection.concurrent.TrieMap
 import akka.actor._
-import kamon.util.{ FastDispatch, TriemapAtomicGetOrElseUpdate }
-
-object Metrics extends ExtensionId[MetricsExtension] with ExtensionIdProvider {
-  override def get(system: ActorSystem): MetricsExtension = super.get(system)
-  def lookup(): ExtensionId[_ <: actor.Extension] = Metrics
-  def createExtension(system: ExtendedActorSystem): MetricsExtension = new MetricsExtensionImpl(system)
-}
+import kamon.util.{ LazyActorRef, TriemapAtomicGetOrElseUpdate }
 
 case class EntityRegistration[T <: EntityRecorder](entity: Entity, recorder: T)
 
-trait MetricsExtension extends Kamon.Extension {
+trait MetricsExtension {
   def settings: MetricsExtensionSettings
   def shouldTrack(entity: Entity): Boolean
   def shouldTrack(entityName: String, category: String): Boolean =
@@ -63,16 +55,11 @@ trait MetricsExtension extends Kamon.Extension {
   def instrumentFactory(category: String): InstrumentFactory
 }
 
-class MetricsExtensionImpl(system: ExtendedActorSystem) extends MetricsExtension {
-  import FastDispatch.Syntax
-
-  val settings = MetricsExtensionSettings(system)
-
+private[kamon] class MetricsExtensionImpl(config: Config) extends MetricsExtension {
   private val _trackedEntities = TrieMap.empty[Entity, EntityRecorder]
-  private val _collectionContext = buildDefaultCollectionContext
-  private val _metricsCollectionDispatcher = system.dispatchers.lookup(settings.metricCollectionDispatcher)
-  private lazy val _subscriptions = ModuleSupervisor.get(system).createModule("subscriptions-dispatcher",
-    SubscriptionsDispatcher.props(settings.tickInterval, collectSnapshots).withDispatcher(settings.metricCollectionDispatcher))
+  private val _subscriptions = new LazyActorRef
+
+  val settings = MetricsExtensionSettings(config)
 
   def shouldTrack(entity: Entity): Boolean =
     settings.entityFilters.get(entity.category).map {
@@ -110,10 +97,10 @@ class MetricsExtensionImpl(system: ExtendedActorSystem) extends MetricsExtension
     find(Entity(name, category))
 
   def subscribe(filter: SubscriptionFilter, subscriber: ActorRef, permanent: Boolean): Unit =
-    _subscriptions.fastDispatch(Subscribe(filter, subscriber, permanent))(_metricsCollectionDispatcher)
+    _subscriptions.tell(Subscribe(filter, subscriber, permanent))
 
   def unsubscribe(subscriber: ActorRef): Unit =
-    _subscriptions.fastDispatch(Unsubscribe(subscriber))(_metricsCollectionDispatcher)
+    _subscriptions.tell(Unsubscribe(subscriber))
 
   def buildDefaultCollectionContext: CollectionContext =
     CollectionContext(settings.defaultCollectionContextBufferSize)
@@ -121,16 +108,34 @@ class MetricsExtensionImpl(system: ExtendedActorSystem) extends MetricsExtension
   def instrumentFactory(category: String): InstrumentFactory =
     settings.instrumentFactories.getOrElse(category, settings.defaultInstrumentFactory)
 
-  /**
-   *  Collect and dispatch.
-   */
-  private def collectSnapshots(): Map[Entity, EntitySnapshot] = {
+  private[kamon] def collectSnapshots(collectionContext: CollectionContext): Map[Entity, EntitySnapshot] = {
     val builder = Map.newBuilder[Entity, EntitySnapshot]
     _trackedEntities.foreach {
-      case (identity, recorder) ⇒ builder += ((identity, recorder.collect(_collectionContext)))
+      case (identity, recorder) ⇒ builder += ((identity, recorder.collect(collectionContext)))
     }
 
     builder.result()
   }
+
+  /**
+   *  Metrics Extension initialization.
+   */
+  private var _system: ActorSystem = null
+  private lazy val _start = {
+    _subscriptions.point(_system.actorOf(SubscriptionsDispatcher.props(settings.tickInterval, this), "metrics"))
+    settings.pointScheduler(DefaultRefreshScheduler(_system.scheduler, _system.dispatcher))
+  }
+
+  def start(system: ActorSystem): Unit = synchronized {
+    _system = system
+    _start
+    _system = null
+  }
+}
+
+private[kamon] object MetricsExtensionImpl {
+
+  def apply(config: Config) =
+    new MetricsExtensionImpl(config)
 }
 
diff --git a/kamon-core/src/main/scala/kamon/metric/MetricsExtensionSettings.scala b/kamon-core/src/main/scala/kamon/metric/MetricsExtensionSettings.scala
index 84624336..9881ed00 100644
--- a/kamon-core/src/main/scala/kamon/metric/MetricsExtensionSettings.scala
+++ b/kamon-core/src/main/scala/kamon/metric/MetricsExtensionSettings.scala
@@ -16,9 +16,8 @@
 
 package kamon.metric
 
-import akka.actor.ExtendedActorSystem
 import com.typesafe.config.Config
-import kamon.metric.instrument.{ RefreshScheduler, InstrumentFactory, DefaultInstrumentSettings, InstrumentCustomSettings }
+import kamon.metric.instrument._
 import kamon.util.GlobPathFilter
 
 import scala.concurrent.duration.FiniteDuration
@@ -27,15 +26,19 @@ import scala.concurrent.duration.FiniteDuration
  *  Configuration settings for the Metrics extension, as read from the `kamon.metric` configuration key.
  */
 case class MetricsExtensionSettings(
-  tickInterval: FiniteDuration,
-  defaultCollectionContextBufferSize: Int,
-  trackUnmatchedEntities: Boolean,
-  entityFilters: Map[String, EntityFilter],
-  instrumentFactories: Map[String, InstrumentFactory],
-  defaultInstrumentFactory: InstrumentFactory,
-  metricCollectionDispatcher: String,
-  refreshSchedulerDispatcher: String,
-  refreshScheduler: RefreshScheduler)
+    tickInterval: FiniteDuration,
+    defaultCollectionContextBufferSize: Int,
+    trackUnmatchedEntities: Boolean,
+    entityFilters: Map[String, EntityFilter],
+    instrumentFactories: Map[String, InstrumentFactory],
+    defaultInstrumentFactory: InstrumentFactory,
+    refreshScheduler: RefreshScheduler) {
+
+  private[kamon] def pointScheduler(targetScheduler: RefreshScheduler): Unit = refreshScheduler match {
+    case lrs: LazyRefreshScheduler ⇒ lrs.point(targetScheduler)
+    case others                    ⇒
+  }
+}
 
 /**
  *
@@ -49,23 +52,21 @@ object MetricsExtensionSettings {
   import kamon.util.ConfigTools.Syntax
   import scala.concurrent.duration._
 
-  def apply(system: ExtendedActorSystem): MetricsExtensionSettings = {
-    val metricConfig = system.settings.config.getConfig("kamon.metric")
+  def apply(config: Config): MetricsExtensionSettings = {
+    val metricConfig = config.getConfig("kamon.metric")
 
     val tickInterval = metricConfig.getFiniteDuration("tick-interval")
     val collectBufferSize = metricConfig.getInt("default-collection-context-buffer-size")
     val trackUnmatchedEntities = metricConfig.getBoolean("track-unmatched-entities")
     val entityFilters = loadFilters(metricConfig.getConfig("filters"))
     val defaultInstrumentSettings = DefaultInstrumentSettings.fromConfig(metricConfig.getConfig("default-instrument-settings"))
-    val metricCollectionDispatcher = metricConfig.getString("dispatchers.metric-collection")
-    val refreshSchedulerDispatcher = metricConfig.getString("dispatchers.refresh-scheduler")
 
-    val refreshScheduler = RefreshScheduler(system.scheduler, system.dispatchers.lookup(refreshSchedulerDispatcher))
+    val refreshScheduler = new LazyRefreshScheduler
     val instrumentFactories = loadInstrumentFactories(metricConfig.getConfig("instrument-settings"), defaultInstrumentSettings, refreshScheduler)
     val defaultInstrumentFactory = new InstrumentFactory(Map.empty, defaultInstrumentSettings, refreshScheduler)
 
     MetricsExtensionSettings(tickInterval, collectBufferSize, trackUnmatchedEntities, entityFilters, instrumentFactories,
-      defaultInstrumentFactory, metricCollectionDispatcher, refreshSchedulerDispatcher, refreshScheduler)
+      defaultInstrumentFactory, refreshScheduler)
   }
 
   /**
diff --git a/kamon-core/src/main/scala/kamon/metric/SubscriptionsDispatcher.scala b/kamon-core/src/main/scala/kamon/metric/SubscriptionsDispatcher.scala
index f616be35..68b545a5 100644
--- a/kamon-core/src/main/scala/kamon/metric/SubscriptionsDispatcher.scala
+++ b/kamon-core/src/main/scala/kamon/metric/SubscriptionsDispatcher.scala
@@ -24,11 +24,12 @@ import scala.concurrent.duration.FiniteDuration
 /**
  *  Manages subscriptions to metrics and dispatch snapshots on every tick to all subscribers.
  */
-private[kamon] class SubscriptionsDispatcher(interval: FiniteDuration, collector: () ⇒ Map[Entity, EntitySnapshot]) extends Actor {
+private[kamon] class SubscriptionsDispatcher(interval: FiniteDuration, metricsExtension: MetricsExtensionImpl) extends Actor {
   var lastTick = MilliTimestamp.now
   var oneShotSubscriptions = Map.empty[ActorRef, SubscriptionFilter]
   var permanentSubscriptions = Map.empty[ActorRef, SubscriptionFilter]
   val tickSchedule = context.system.scheduler.schedule(interval, interval, self, Tick)(context.dispatcher)
+  val collectionContext = metricsExtension.buildDefaultCollectionContext
 
   def receive = {
     case Tick                                       ⇒ processTick()
@@ -38,7 +39,7 @@ private[kamon] class SubscriptionsDispatcher(interval: FiniteDuration, collector
   }
 
   def processTick(): Unit =
-    dispatch(collector())
+    dispatch(metricsExtension.collectSnapshots(collectionContext))
 
   def subscribe(filter: SubscriptionFilter, subscriber: ActorRef, permanent: Boolean): Unit = {
     def addSubscription(storage: Map[ActorRef, SubscriptionFilter]): Map[ActorRef, SubscriptionFilter] =
@@ -80,8 +81,8 @@ private[kamon] class SubscriptionsDispatcher(interval: FiniteDuration, collector
 }
 
 object SubscriptionsDispatcher {
-  def props(interval: FiniteDuration, collector: () ⇒ Map[Entity, EntitySnapshot]): Props =
-    Props(new SubscriptionsDispatcher(interval, collector))
+  def props(interval: FiniteDuration, metricsExtension: MetricsExtensionImpl): Props =
+    Props(new SubscriptionsDispatcher(interval, metricsExtension))
 
   case object Tick
   case class Unsubscribe(subscriber: ActorRef)
diff --git a/kamon-core/src/main/scala/kamon/metric/TickMetricSnapshotBuffer.scala b/kamon-core/src/main/scala/kamon/metric/TickMetricSnapshotBuffer.scala
index 358dade8..dfc5d5f0 100644
--- a/kamon-core/src/main/scala/kamon/metric/TickMetricSnapshotBuffer.scala
+++ b/kamon-core/src/main/scala/kamon/metric/TickMetricSnapshotBuffer.scala
@@ -29,7 +29,7 @@ class TickMetricSnapshotBuffer(flushInterval: FiniteDuration, receiver: ActorRef
   import MapMerge.Syntax
 
   val flushSchedule = context.system.scheduler.schedule(flushInterval, flushInterval, self, FlushBuffer)(context.dispatcher)
-  val collectionContext: CollectionContext = Kamon(Metrics)(context.system).buildDefaultCollectionContext
+  val collectionContext: CollectionContext = Kamon.metrics.buildDefaultCollectionContext
 
   def receive = empty
 
diff --git a/kamon-core/src/main/scala/kamon/metric/UserMetrics.scala b/kamon-core/src/main/scala/kamon/metric/UserMetrics.scala
index e6ec5e99..e0818292 100644
--- a/kamon-core/src/main/scala/kamon/metric/UserMetrics.scala
+++ b/kamon-core/src/main/scala/kamon/metric/UserMetrics.scala
@@ -16,30 +16,13 @@
 
 package kamon.metric
 
-import akka.actor
-import akka.actor.{ ActorSystem, ExtendedActorSystem, ExtensionIdProvider, ExtensionId }
-import kamon.Kamon
 import kamon.metric.instrument.Gauge.CurrentValueCollector
 import kamon.metric.instrument.Histogram.DynamicRange
 import kamon.metric.instrument._
 
 import scala.concurrent.duration.FiniteDuration
 
-object UserMetrics extends ExtensionId[UserMetricsExtension] with ExtensionIdProvider {
-  override def get(system: ActorSystem): UserMetricsExtension = super.get(system)
-  def lookup(): ExtensionId[_ <: actor.Extension] = UserMetrics
-  def createExtension(system: ExtendedActorSystem): UserMetricsExtension = {
-    val metricsExtension = Metrics.get(system)
-    val instrumentFactory = metricsExtension.instrumentFactory(entity.category)
-    val userMetricsExtension = new UserMetricsExtensionImpl(instrumentFactory)
-
-    metricsExtension.register(entity, userMetricsExtension).recorder
-  }
-
-  val entity = Entity("user-metric", "user-metric")
-}
-
-trait UserMetricsExtension extends Kamon.Extension {
+trait UserMetricsExtension {
   def histogram(name: String): Histogram
   def histogram(name: String, dynamicRange: DynamicRange): Histogram
   def histogram(name: String, unitOfMeasurement: UnitOfMeasurement): Histogram
@@ -86,7 +69,7 @@ trait UserMetricsExtension extends Kamon.Extension {
 
 }
 
-class UserMetricsExtensionImpl(instrumentFactory: InstrumentFactory) extends GenericEntityRecorder(instrumentFactory) with UserMetricsExtension {
+private[kamon] class UserMetricsExtensionImpl(instrumentFactory: InstrumentFactory) extends GenericEntityRecorder(instrumentFactory) with UserMetricsExtension {
   override def histogram(name: String): Histogram =
     super.histogram(name)
 
@@ -206,4 +189,16 @@ class UserMetricsExtensionImpl(instrumentFactory: InstrumentFactory) extends Gen
 
   override def removeCounter(key: CounterKey): Unit =
     super.removeCounter(key)
+}
+
+private[kamon] object UserMetricsExtensionImpl {
+  val UserMetricEntity = Entity("user-metric", "user-metric")
+
+  def apply(metricsExtension: MetricsExtension): UserMetricsExtensionImpl = {
+    val instrumentFactory = metricsExtension.instrumentFactory(UserMetricEntity.category)
+    val userMetricsExtension = new UserMetricsExtensionImpl(instrumentFactory)
+
+    metricsExtension.register(UserMetricEntity, userMetricsExtension).recorder
+  }
+
 }
\ No newline at end of file
diff --git a/kamon-core/src/main/scala/kamon/metric/instrument/Instrument.scala b/kamon-core/src/main/scala/kamon/metric/instrument/Instrument.scala
index 68d5c876..59b4b443 100644
--- a/kamon-core/src/main/scala/kamon/metric/instrument/Instrument.scala
+++ b/kamon-core/src/main/scala/kamon/metric/instrument/Instrument.scala
@@ -51,22 +51,3 @@ object CollectionContext {
   }
 }
 
-trait RefreshScheduler {
-  def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable
-}
-
-object RefreshScheduler {
-  val NoopScheduler = new RefreshScheduler {
-    def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable = new Cancellable {
-      override def isCancelled: Boolean = true
-      override def cancel(): Boolean = true
-    }
-  }
-
-  def apply(scheduler: Scheduler, dispatcher: MessageDispatcher): RefreshScheduler = new RefreshScheduler {
-    def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable =
-      scheduler.schedule(interval, interval)(refresh.apply())(dispatcher)
-  }
-
-  def create(scheduler: Scheduler, dispatcher: MessageDispatcher): RefreshScheduler = apply(scheduler, dispatcher)
-}
\ No newline at end of file
diff --git a/kamon-core/src/main/scala/kamon/metric/instrument/RefreshScheduler.scala b/kamon-core/src/main/scala/kamon/metric/instrument/RefreshScheduler.scala
new file mode 100644
index 00000000..adb08713
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/metric/instrument/RefreshScheduler.scala
@@ -0,0 +1,99 @@
+package kamon.metric.instrument
+
+import akka.actor.{ Scheduler, Cancellable }
+import org.HdrHistogram.WriterReaderPhaser
+
+import scala.collection.concurrent.TrieMap
+import scala.concurrent.ExecutionContext
+import scala.concurrent.duration.FiniteDuration
+
+trait RefreshScheduler {
+  def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable
+}
+
+/**
+ *  Default implementation of RefreshScheduler that simply uses an [[akka.actor.Scheduler]] to schedule tasks to be run
+ *  in the provided ExecutionContext.
+ */
+class DefaultRefreshScheduler(scheduler: Scheduler, dispatcher: ExecutionContext) extends RefreshScheduler {
+  def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable =
+    scheduler.schedule(interval, interval)(refresh.apply())(dispatcher)
+}
+
+object DefaultRefreshScheduler {
+  def apply(scheduler: Scheduler, dispatcher: ExecutionContext): RefreshScheduler =
+    new DefaultRefreshScheduler(scheduler, dispatcher)
+
+  def create(scheduler: Scheduler, dispatcher: ExecutionContext): RefreshScheduler =
+    apply(scheduler, dispatcher)
+}
+
+/**
+ *  RefreshScheduler implementation that accumulates all the scheduled actions until it is pointed to another refresh
+ *  scheduler. Once it is pointed, all subsequent calls to `schedule` will immediately be scheduled in the pointed
+ *  scheduler.
+ */
+class LazyRefreshScheduler extends RefreshScheduler {
+  private val _schedulerPhaser = new WriterReaderPhaser
+  private val _backlog = new TrieMap[(FiniteDuration, () ⇒ Unit), RepointableCancellable]()
+  @volatile private var _target: Option[RefreshScheduler] = None
+
+  def schedule(interval: FiniteDuration, refresh: () ⇒ Unit): Cancellable = {
+    val criticalEnter = _schedulerPhaser.writerCriticalSectionEnter()
+    try {
+      _target.map { scheduler ⇒
+        scheduler.schedule(interval, refresh)
+
+      } getOrElse {
+        val entry = (interval, refresh)
+        val cancellable = new RepointableCancellable(entry)
+
+        _backlog.put(entry, cancellable)
+        cancellable
+      }
+
+    } finally {
+      _schedulerPhaser.writerCriticalSectionExit(criticalEnter)
+    }
+  }
+
+  def point(target: RefreshScheduler): Unit = try {
+    _schedulerPhaser.readerLock()
+
+    if (_target.isEmpty) {
+      _target = Some(target)
+      _schedulerPhaser.flipPhase(10000L)
+      _backlog.dropWhile {
+        case ((interval, refresh), repointableCancellable) ⇒
+          repointableCancellable.point(target.schedule(interval, refresh))
+          true
+      }
+    } else sys.error("A LazyRefreshScheduler cannot be pointed more than once.")
+  } finally { _schedulerPhaser.readerUnlock() }
+
+  class RepointableCancellable(entry: (FiniteDuration, () ⇒ Unit)) extends Cancellable {
+    private var _isCancelled = false
+    private var _cancellable: Option[Cancellable] = None
+
+    def isCancelled: Boolean = synchronized {
+      _cancellable.map(_.isCancelled).getOrElse(_isCancelled)
+    }
+
+    def cancel(): Boolean = synchronized {
+      _isCancelled = true
+      _cancellable.map(_.cancel()).getOrElse(_backlog.remove(entry).nonEmpty)
+    }
+
+    def point(cancellable: Cancellable): Unit = synchronized {
+      if (_cancellable.isEmpty) {
+        _cancellable = Some(cancellable)
+
+        if (_isCancelled)
+          cancellable.cancel()
+
+      } else sys.error("A RepointableCancellable cannot be pointed more than once.")
+
+    }
+  }
+}
+
diff --git a/kamon-core/src/main/scala/kamon/trace/MetricsOnlyContext.scala b/kamon-core/src/main/scala/kamon/trace/MetricsOnlyContext.scala
index e62178dd..5f7fdff5 100644
--- a/kamon-core/src/main/scala/kamon/trace/MetricsOnlyContext.scala
+++ b/kamon-core/src/main/scala/kamon/trace/MetricsOnlyContext.scala
@@ -18,16 +18,14 @@ package kamon.trace
 
 import java.util.concurrent.ConcurrentLinkedQueue
 
-import akka.actor.{ ExtensionId, ActorSystem }
 import akka.event.LoggingAdapter
-import kamon.Kamon.Extension
 import kamon.metric.{ MetricsExtension, TraceMetrics }
 import kamon.util.{ NanoInterval, RelativeNanoTimestamp }
 
 import scala.annotation.tailrec
 
 private[kamon] class MetricsOnlyContext(traceName: String, val token: String, izOpen: Boolean, val levelOfDetail: LevelOfDetail,
-  val startTimestamp: RelativeNanoTimestamp, log: LoggingAdapter, metricsExtension: MetricsExtension, val actorSystem: ActorSystem)
+  val startTimestamp: RelativeNanoTimestamp, log: LoggingAdapter, metricsExtension: MetricsExtension)
     extends TraceContext {
 
   @volatile private var _name = traceName
@@ -48,8 +46,6 @@ private[kamon] class MetricsOnlyContext(traceName: String, val token: String, iz
   def isOpen: Boolean = _isOpen
   def addMetadata(key: String, value: String): Unit = {}
 
-  def lookupExtension[T <: Extension](id: ExtensionId[T]): T = id(actorSystem)
-
   def finish(): Unit = {
     _isOpen = false
     val traceElapsedTime = NanoInterval.since(startTimestamp)
diff --git a/kamon-core/src/main/scala/kamon/trace/TraceContext.scala b/kamon-core/src/main/scala/kamon/trace/TraceContext.scala
index ed8170a9..48e56153 100644
--- a/kamon-core/src/main/scala/kamon/trace/TraceContext.scala
+++ b/kamon-core/src/main/scala/kamon/trace/TraceContext.scala
@@ -17,12 +17,8 @@
 package kamon.trace
 
 import java.io.ObjectStreamException
-import akka.actor.{ ExtensionId, ActorSystem }
-import kamon.Kamon.Extension
-import kamon._
-import kamon.metric._
 import kamon.trace.TraceContextAware.DefaultTraceContextAware
-import kamon.util.{ NanoInterval, RelativeNanoTimestamp }
+import kamon.util.RelativeNanoTimestamp
 
 trait TraceContext {
   def name: String
@@ -39,8 +35,6 @@ trait TraceContext {
   def addMetadata(key: String, value: String)
 
   def startTimestamp: RelativeNanoTimestamp
-
-  def lookupExtension[T <: Kamon.Extension](id: ExtensionId[T]): T
 }
 
 object TraceContext {
@@ -99,9 +93,6 @@ case object EmptyTraceContext extends TraceContext {
   def addMetadata(key: String, value: String): Unit = {}
   def startTimestamp = new RelativeNanoTimestamp(0L)
 
-  override def lookupExtension[T <: Extension](id: ExtensionId[T]): T =
-    sys.error("Can't lookup extensions on a EmptyTraceContext.")
-
   case object EmptySegment extends Segment {
     val name: String = "empty-segment"
     val category: String = "empty-category"
diff --git a/kamon-core/src/main/scala/kamon/trace/TracerExtension.scala b/kamon-core/src/main/scala/kamon/trace/TracerExtension.scala
index 41dcd6bc..be565154 100644
--- a/kamon-core/src/main/scala/kamon/trace/TracerExtension.scala
+++ b/kamon-core/src/main/scala/kamon/trace/TracerExtension.scala
@@ -20,20 +20,13 @@ import java.net.InetAddress
 import java.util.concurrent.atomic.AtomicLong
 
 import akka.actor._
-import akka.actor
-import kamon.Kamon
-import kamon.metric.{ Metrics, MetricsExtension }
-import kamon.util.{ NanoInterval, RelativeNanoTimestamp, NanoTimestamp, GlobPathFilter }
+import com.typesafe.config.Config
+import kamon.metric.MetricsExtension
+import kamon.util._
 
 import scala.util.Try
 
-object Tracer extends ExtensionId[TracerExtension] with ExtensionIdProvider {
-  override def get(system: ActorSystem): TracerExtension = super.get(system)
-  def lookup(): ExtensionId[_ <: actor.Extension] = Tracer
-  def createExtension(system: ExtendedActorSystem): TracerExtension = new TracerExtensionImpl(system)
-}
-
-trait TracerExtension extends Kamon.Extension {
+trait TracerExtension {
   def newContext(name: String): TraceContext
   def newContext(name: String, token: String): TraceContext
   def newContext(name: String, token: String, timestamp: RelativeNanoTimestamp, isOpen: Boolean, isLocal: Boolean): TraceContext
@@ -42,14 +35,13 @@ trait TracerExtension extends Kamon.Extension {
   def unsubscribe(subscriber: ActorRef): Unit
 }
 
-class TracerExtensionImpl(system: ExtendedActorSystem) extends TracerExtension {
-  private val _settings = TraceSettings(system)
-  private val _metricsExtension = Metrics.get(system)
-
+private[kamon] class TracerExtensionImpl(metricsExtension: MetricsExtension, config: Config) extends TracerExtension {
+  private val _settings = TraceSettings(config)
   private val _hostnamePrefix = Try(InetAddress.getLocalHost.getHostName).getOrElse("unknown-localhost")
   private val _tokenCounter = new AtomicLong
-  private val _subscriptions = system.actorOf(Props[TraceSubscriptions], "trace-subscriptions")
-  private val _incubator = system.actorOf(Incubator.props(_subscriptions))
+
+  private val _subscriptions = new LazyActorRef
+  private val _incubator = new LazyActorRef
 
   private def newToken: String =
     _hostnamePrefix + "-" + String.valueOf(_tokenCounter.incrementAndGet())
@@ -66,7 +58,7 @@ class TracerExtensionImpl(system: ExtendedActorSystem) extends TracerExtension {
   private def createTraceContext(traceName: String, token: String = newToken, startTimestamp: RelativeNanoTimestamp = RelativeNanoTimestamp.now,
     isOpen: Boolean = true, isLocal: Boolean = true): TraceContext = {
 
-    def newMetricsOnlyContext = new MetricsOnlyContext(traceName, token, isOpen, _settings.levelOfDetail, startTimestamp, null, _metricsExtension, system)
+    def newMetricsOnlyContext = new MetricsOnlyContext(traceName, token, isOpen, _settings.levelOfDetail, startTimestamp, null, metricsExtension)
 
     if (_settings.levelOfDetail == LevelOfDetail.MetricsOnly || !isLocal)
       newMetricsOnlyContext
@@ -74,20 +66,44 @@ class TracerExtensionImpl(system: ExtendedActorSystem) extends TracerExtension {
       if (!_settings.sampler.shouldTrace)
         newMetricsOnlyContext
       else
-        new TracingContext(traceName, token, true, _settings.levelOfDetail, isLocal, startTimestamp, null, _metricsExtension, this, system, dispatchTracingContext)
+        new TracingContext(traceName, token, true, _settings.levelOfDetail, isLocal, startTimestamp, null, metricsExtension, this, dispatchTracingContext)
     }
   }
 
-  def subscribe(subscriber: ActorRef): Unit = _subscriptions ! TraceSubscriptions.Subscribe(subscriber)
-  def unsubscribe(subscriber: ActorRef): Unit = _subscriptions ! TraceSubscriptions.Unsubscribe(subscriber)
+  def subscribe(subscriber: ActorRef): Unit =
+    _subscriptions.tell(TraceSubscriptions.Subscribe(subscriber))
+
+  def unsubscribe(subscriber: ActorRef): Unit =
+    _subscriptions.tell(TraceSubscriptions.Unsubscribe(subscriber))
 
   private[kamon] def dispatchTracingContext(trace: TracingContext): Unit =
     if (_settings.sampler.shouldReport(trace.elapsedTime))
       if (trace.shouldIncubate)
-        _incubator ! trace
+        _incubator.tell(trace)
       else
-        _subscriptions ! trace.generateTraceInfo
+        _subscriptions.tell(trace.generateTraceInfo)
+
+  /**
+   *  Tracer Extension initialization.
+   */
+  private var _system: ActorSystem = null
+  private lazy val _start = {
+    val subscriptions = _system.actorOf(Props[TraceSubscriptions], "trace-subscriptions")
+    _subscriptions.point(subscriptions)
+    _incubator.point(_system.actorOf(Incubator.props(subscriptions)))
+  }
+
+  def start(system: ActorSystem): Unit = synchronized {
+    _system = system
+    _start
+    _system = null
+  }
+}
+
+private[kamon] object TracerExtensionImpl {
 
+  def apply(metricsExtension: MetricsExtension, config: Config) =
+    new TracerExtensionImpl(metricsExtension, config)
 }
 
 case class TraceInfo(name: String, token: String, timestamp: NanoTimestamp, elapsedTime: NanoInterval, metadata: Map[String, String], segments: List[SegmentInfo])
diff --git a/kamon-core/src/main/scala/kamon/trace/TracerExtensionSettings.scala b/kamon-core/src/main/scala/kamon/trace/TracerExtensionSettings.scala
index d360330d..7510ab7f 100644
--- a/kamon-core/src/main/scala/kamon/trace/TracerExtensionSettings.scala
+++ b/kamon-core/src/main/scala/kamon/trace/TracerExtensionSettings.scala
@@ -18,13 +18,13 @@ package kamon.trace
 
 import java.util.concurrent.TimeUnit
 
-import akka.actor.ActorSystem
+import com.typesafe.config.Config
 
 case class TraceSettings(levelOfDetail: LevelOfDetail, sampler: Sampler)
 
 object TraceSettings {
-  def apply(system: ActorSystem): TraceSettings = {
-    val tracerConfig = system.settings.config.getConfig("kamon.trace")
+  def apply(config: Config): TraceSettings = {
+    val tracerConfig = config.getConfig("kamon.trace")
 
     val detailLevel: LevelOfDetail = tracerConfig.getString("level-of-detail") match {
       case "metrics-only" ⇒ LevelOfDetail.MetricsOnly
diff --git a/kamon-core/src/main/scala/kamon/trace/TracingContext.scala b/kamon-core/src/main/scala/kamon/trace/TracingContext.scala
index dd4c3c1a..3d324886 100644
--- a/kamon-core/src/main/scala/kamon/trace/TracingContext.scala
+++ b/kamon-core/src/main/scala/kamon/trace/TracingContext.scala
@@ -19,7 +19,6 @@ package kamon.trace
 import java.util.concurrent.ConcurrentLinkedQueue
 import java.util.concurrent.atomic.AtomicInteger
 
-import akka.actor.ActorSystem
 import akka.event.LoggingAdapter
 import kamon.util.{ NanoInterval, RelativeNanoTimestamp, NanoTimestamp }
 import kamon.metric.MetricsExtension
@@ -28,8 +27,8 @@ import scala.collection.concurrent.TrieMap
 
 private[trace] class TracingContext(traceName: String, token: String, izOpen: Boolean, levelOfDetail: LevelOfDetail,
   isLocal: Boolean, startTimeztamp: RelativeNanoTimestamp, log: LoggingAdapter, metricsExtension: MetricsExtension,
-  traceExtension: TracerExtensionImpl, system: ActorSystem, traceInfoSink: TracingContext ⇒ Unit)
-    extends MetricsOnlyContext(traceName, token, izOpen, levelOfDetail, startTimeztamp, log, metricsExtension, system) {
+  traceExtension: TracerExtensionImpl, traceInfoSink: TracingContext ⇒ Unit)
+    extends MetricsOnlyContext(traceName, token, izOpen, levelOfDetail, startTimeztamp, log, metricsExtension) {
 
   private val _openSegments = new AtomicInteger(0)
   private val _startTimestamp = NanoTimestamp.now
diff --git a/kamon-core/src/main/scala/kamon/util/LazyActorRef.scala b/kamon-core/src/main/scala/kamon/util/LazyActorRef.scala
new file mode 100644
index 00000000..855bf1fc
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/util/LazyActorRef.scala
@@ -0,0 +1,53 @@
+package kamon.util
+
+import java.util
+import java.util.concurrent.ConcurrentLinkedQueue
+
+import akka.actor.{ Actor, ActorRef }
+import org.HdrHistogram.WriterReaderPhaser
+
+import scala.annotation.tailrec
+
+/**
+ *  A LazyActorRef accumulates messages sent to an actor that doesn't exist yet. Once the actor is created and
+ *  the LazyActorRef is pointed to it, all the accumulated messages are flushed and any new message sent to the
+ *  LazyActorRef will immediately be sent to the pointed ActorRef.
+ *
+ *  This is intended to be used during Kamon's initialization where some components need to use ActorRefs to work
+ *  (like subscriptions and the trace incubator) but our internal ActorSystem is not yet ready to create the
+ *  required actors.
+ */
+class LazyActorRef {
+  private val _refPhaser = new WriterReaderPhaser
+  private val _backlog = new ConcurrentLinkedQueue[(Any, ActorRef)]()
+  @volatile private var _target: Option[ActorRef] = None
+
+  def tell(message: Any)(implicit sender: ActorRef = Actor.noSender): Unit = {
+    val criticalEnter = _refPhaser.writerCriticalSectionEnter()
+    try {
+      _target.map(_.tell(message, sender)) getOrElse {
+        _backlog.add((message, sender))
+      }
+
+    } finally { _refPhaser.writerCriticalSectionExit(criticalEnter) }
+  }
+
+  def point(target: ActorRef): Unit = {
+    @tailrec def drain(q: util.Queue[(Any, ActorRef)]): Unit = if (!q.isEmpty) {
+      val (msg, sender) = q.poll()
+      target.tell(msg, sender)
+      drain(q)
+    }
+
+    try {
+      _refPhaser.readerLock()
+
+      if (_target.isEmpty) {
+        _target = Some(target)
+        _refPhaser.flipPhase(1000L)
+        drain(_backlog)
+
+      } else sys.error("A LazyActorRef cannot be pointed more than once.")
+    } finally { _refPhaser.readerUnlock() }
+  }
+}
diff --git a/kamon-core/src/test/scala/kamon/metric/SubscriptionsProtocolSpec.scala b/kamon-core/src/test/scala/kamon/metric/SubscriptionsProtocolSpec.scala
index 7dbcafd7..53ae5273 100644
--- a/kamon-core/src/test/scala/kamon/metric/SubscriptionsProtocolSpec.scala
+++ b/kamon-core/src/test/scala/kamon/metric/SubscriptionsProtocolSpec.scala
@@ -19,6 +19,7 @@ package kamon.metric
 import akka.actor._
 import akka.testkit.{ TestProbe, ImplicitSender }
 import com.typesafe.config.ConfigFactory
+import kamon.Kamon
 import kamon.metric.SubscriptionsDispatcher.TickMetricSnapshot
 import kamon.testkit.BaseKamonSpec
 import scala.concurrent.duration._
@@ -32,7 +33,7 @@ class SubscriptionsProtocolSpec extends BaseKamonSpec("subscriptions-protocol-sp
         |}
       """.stripMargin)
 
-  val metricsModule = kamon.metrics
+  lazy val metricsModule = Kamon.metrics
   import metricsModule.{ register, subscribe, unsubscribe }
 
   "the Subscriptions messaging protocol" should {
diff --git a/kamon-core/src/test/scala/kamon/metric/TickMetricSnapshotBufferSpec.scala b/kamon-core/src/test/scala/kamon/metric/TickMetricSnapshotBufferSpec.scala
index 2e1f246d..0c9ced32 100644
--- a/kamon-core/src/test/scala/kamon/metric/TickMetricSnapshotBufferSpec.scala
+++ b/kamon-core/src/test/scala/kamon/metric/TickMetricSnapshotBufferSpec.scala
@@ -17,6 +17,7 @@
 package kamon.metric
 
 import com.typesafe.config.ConfigFactory
+import kamon.Kamon
 import kamon.metric.instrument.Histogram.MutableRecord
 import kamon.testkit.BaseKamonSpec
 import kamon.util.MilliTimestamp
@@ -85,9 +86,9 @@ class TickMetricSnapshotBufferSpec extends BaseKamonSpec("trace-metrics-spec") w
   }
 
   trait SnapshotFixtures {
-    val collectionContext = kamon.metrics.buildDefaultCollectionContext
+    val collectionContext = Kamon.metrics.buildDefaultCollectionContext
     val testTraceIdentity = Entity("buffer-spec-test-trace", "trace")
-    val traceRecorder = kamon.metrics.register(TraceMetrics, "buffer-spec-test-trace").get.recorder
+    val traceRecorder = Kamon.metrics.register(TraceMetrics, "buffer-spec-test-trace").get.recorder
 
     val firstEmpty = TickMetricSnapshot(new MilliTimestamp(1000), new MilliTimestamp(2000), Map.empty)
     val secondEmpty = TickMetricSnapshot(new MilliTimestamp(2000), new MilliTimestamp(3000), Map.empty)
diff --git a/kamon-core/src/test/scala/kamon/metric/UserMetricsSpec.scala b/kamon-core/src/test/scala/kamon/metric/UserMetricsSpec.scala
index 7b6cbebc..455518f8 100644
--- a/kamon-core/src/test/scala/kamon/metric/UserMetricsSpec.scala
+++ b/kamon-core/src/test/scala/kamon/metric/UserMetricsSpec.scala
@@ -17,6 +17,7 @@
 package kamon.metric
 
 import com.typesafe.config.ConfigFactory
+import kamon.Kamon
 import kamon.metric.instrument.Histogram.DynamicRange
 import kamon.testkit.BaseKamonSpec
 import scala.concurrent.duration._
@@ -34,54 +35,54 @@ class UserMetricsSpec extends BaseKamonSpec("user-metrics-spec") {
   "the UserMetrics extension" should {
 
     "allow registering a fully configured Histogram and get the same Histogram if registering again" in {
-      val histogramA = kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
-      val histogramB = kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
+      val histogramA = Kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
+      val histogramB = Kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
 
       histogramA shouldBe theSameInstanceAs(histogramB)
     }
 
     "return the original Histogram when registering a fully configured Histogram for second time but with different settings" in {
-      val histogramA = kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
-      val histogramB = kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 50000, 2))
+      val histogramA = Kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 10000, 2))
+      val histogramB = Kamon.userMetrics.histogram("histogram-with-settings", DynamicRange(1, 50000, 2))
 
       histogramA shouldBe theSameInstanceAs(histogramB)
     }
 
     "allow registering a Histogram that takes the default configuration from the kamon.metrics.precision settings" in {
-      kamon.userMetrics.histogram("histogram-with-default-configuration")
+      Kamon.userMetrics.histogram("histogram-with-default-configuration")
     }
 
     "allow registering a Counter and get the same Counter if registering again" in {
-      val counterA = kamon.userMetrics.counter("counter")
-      val counterB = kamon.userMetrics.counter("counter")
+      val counterA = Kamon.userMetrics.counter("counter")
+      val counterB = Kamon.userMetrics.counter("counter")
 
       counterA shouldBe theSameInstanceAs(counterB)
     }
 
     "allow registering a fully configured MinMaxCounter and get the same MinMaxCounter if registering again" in {
-      val minMaxCounterA = kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
-      val minMaxCounterB = kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
+      val minMaxCounterA = Kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
+      val minMaxCounterB = Kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
 
       minMaxCounterA shouldBe theSameInstanceAs(minMaxCounterB)
     }
 
     "return the original MinMaxCounter when registering a fully configured MinMaxCounter for second time but with different settings" in {
-      val minMaxCounterA = kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
-      val minMaxCounterB = kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 50000, 2), 1 second)
+      val minMaxCounterA = Kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 10000, 2), 1 second)
+      val minMaxCounterB = Kamon.userMetrics.minMaxCounter("min-max-counter-with-settings", DynamicRange(1, 50000, 2), 1 second)
 
       minMaxCounterA shouldBe theSameInstanceAs(minMaxCounterB)
     }
 
     "allow registering a MinMaxCounter that takes the default configuration from the kamon.metrics.precision settings" in {
-      kamon.userMetrics.minMaxCounter("min-max-counter-with-default-configuration")
+      Kamon.userMetrics.minMaxCounter("min-max-counter-with-default-configuration")
     }
 
     "allow registering a fully configured Gauge and get the same Gauge if registering again" in {
-      val gaugeA = kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
+      val gaugeA = Kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
         () ⇒ 1L
       })
 
-      val gaugeB = kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
+      val gaugeB = Kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
         () ⇒ 1L
       })
 
@@ -89,11 +90,11 @@ class UserMetricsSpec extends BaseKamonSpec("user-metrics-spec") {
     }
 
     "return the original Gauge when registering a fully configured Gauge for second time but with different settings" in {
-      val gaugeA = kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
+      val gaugeA = Kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
         () ⇒ 1L
       })
 
-      val gaugeB = kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
+      val gaugeB = Kamon.userMetrics.gauge("gauge-with-settings", DynamicRange(1, 10000, 2), 1 second, {
         () ⇒ 1L
       })
 
@@ -101,26 +102,26 @@ class UserMetricsSpec extends BaseKamonSpec("user-metrics-spec") {
     }
 
     "allow registering a Gauge that takes the default configuration from the kamon.metrics.precision settings" in {
-      kamon.userMetrics.gauge("gauge-with-default-configuration", {
+      Kamon.userMetrics.gauge("gauge-with-default-configuration", {
         () ⇒ 2L
       })
     }
 
     "allow un-registering user metrics" in {
-      val counter = kamon.userMetrics.counter("counter-for-remove")
-      val histogram = kamon.userMetrics.histogram("histogram-for-remove")
-      val minMaxCounter = kamon.userMetrics.minMaxCounter("min-max-counter-for-remove")
-      val gauge = kamon.userMetrics.gauge("gauge-for-remove", { () ⇒ 2L })
-
-      kamon.userMetrics.removeCounter("counter-for-remove")
-      kamon.userMetrics.removeHistogram("histogram-for-remove")
-      kamon.userMetrics.removeMinMaxCounter("min-max-counter-for-remove")
-      kamon.userMetrics.removeGauge("gauge-for-remove")
-
-      counter should not be (theSameInstanceAs(kamon.userMetrics.counter("counter-for-remove")))
-      histogram should not be (theSameInstanceAs(kamon.userMetrics.histogram("histogram-for-remove")))
-      minMaxCounter should not be (theSameInstanceAs(kamon.userMetrics.minMaxCounter("min-max-counter-for-remove")))
-      gauge should not be (theSameInstanceAs(kamon.userMetrics.gauge("gauge-for-remove", { () ⇒ 2L })))
+      val counter = Kamon.userMetrics.counter("counter-for-remove")
+      val histogram = Kamon.userMetrics.histogram("histogram-for-remove")
+      val minMaxCounter = Kamon.userMetrics.minMaxCounter("min-max-counter-for-remove")
+      val gauge = Kamon.userMetrics.gauge("gauge-for-remove", { () ⇒ 2L })
+
+      Kamon.userMetrics.removeCounter("counter-for-remove")
+      Kamon.userMetrics.removeHistogram("histogram-for-remove")
+      Kamon.userMetrics.removeMinMaxCounter("min-max-counter-for-remove")
+      Kamon.userMetrics.removeGauge("gauge-for-remove")
+
+      counter should not be (theSameInstanceAs(Kamon.userMetrics.counter("counter-for-remove")))
+      histogram should not be (theSameInstanceAs(Kamon.userMetrics.histogram("histogram-for-remove")))
+      minMaxCounter should not be (theSameInstanceAs(Kamon.userMetrics.minMaxCounter("min-max-counter-for-remove")))
+      gauge should not be (theSameInstanceAs(Kamon.userMetrics.gauge("gauge-for-remove", { () ⇒ 2L })))
     }
   }
 }
diff --git a/kamon-core/src/test/scala/kamon/metric/instrument/GaugeSpec.scala b/kamon-core/src/test/scala/kamon/metric/instrument/GaugeSpec.scala
index bb494d0b..ec07d66c 100644
--- a/kamon-core/src/test/scala/kamon/metric/instrument/GaugeSpec.scala
+++ b/kamon-core/src/test/scala/kamon/metric/instrument/GaugeSpec.scala
@@ -17,6 +17,7 @@
 package kamon.metric.instrument
 
 import java.util.concurrent.atomic.AtomicLong
+import kamon.Kamon
 import kamon.metric.instrument.Histogram.DynamicRange
 import kamon.testkit.BaseKamonSpec
 import scala.concurrent.duration._
@@ -48,7 +49,7 @@ class GaugeSpec extends BaseKamonSpec("gauge-spec") {
 
       Thread.sleep(1.second.toMillis)
       gauge.cleanup
-      val snapshot = gauge.collect(kamon.metrics.buildDefaultCollectionContext)
+      val snapshot = gauge.collect(Kamon.metrics.buildDefaultCollectionContext)
 
       snapshot.numberOfMeasurements should be(10L +- 1L)
       snapshot.min should be(1)
@@ -58,7 +59,7 @@ class GaugeSpec extends BaseKamonSpec("gauge-spec") {
     "not record the current value when doing a collection" in new GaugeFixture {
       val (numberOfValuesRecorded, gauge) = createGauge(10 seconds)
 
-      val snapshot = gauge.collect(kamon.metrics.buildDefaultCollectionContext)
+      val snapshot = gauge.collect(Kamon.metrics.buildDefaultCollectionContext)
       snapshot.numberOfMeasurements should be(0)
       numberOfValuesRecorded.get() should be(0)
     }
@@ -67,7 +68,7 @@ class GaugeSpec extends BaseKamonSpec("gauge-spec") {
   trait GaugeFixture {
     def createGauge(refreshInterval: FiniteDuration = 100 millis): (AtomicLong, Gauge) = {
       val recordedValuesCounter = new AtomicLong(0)
-      val gauge = Gauge(DynamicRange(1, 100, 2), refreshInterval, kamon.metrics.settings.refreshScheduler, {
+      val gauge = Gauge(DynamicRange(1, 100, 2), refreshInterval, Kamon.metrics.settings.refreshScheduler, {
         () ⇒ recordedValuesCounter.addAndGet(1)
       })
 
diff --git a/kamon-core/src/test/scala/kamon/metric/instrument/MinMaxCounterSpec.scala b/kamon-core/src/test/scala/kamon/metric/instrument/MinMaxCounterSpec.scala
index 7a3d7aa3..7acfc229 100644
--- a/kamon-core/src/test/scala/kamon/metric/instrument/MinMaxCounterSpec.scala
+++ b/kamon-core/src/test/scala/kamon/metric/instrument/MinMaxCounterSpec.scala
@@ -19,6 +19,7 @@ import java.nio.LongBuffer
 
 import akka.actor._
 import akka.testkit.TestProbe
+import kamon.Kamon
 import kamon.metric.instrument.Histogram.{ DynamicRange, MutableRecord }
 import kamon.testkit.BaseKamonSpec
 import scala.concurrent.duration._
@@ -109,7 +110,7 @@ class MinMaxCounterSpec extends BaseKamonSpec("min-max-counter-spec") {
       val buffer: LongBuffer = LongBuffer.allocate(64)
     }
 
-    val mmCounter = MinMaxCounter(DynamicRange(1, 1000, 2), 1 hour, kamon.metrics.settings.refreshScheduler)
+    val mmCounter = MinMaxCounter(DynamicRange(1, 1000, 2), 1 hour, Kamon.metrics.settings.refreshScheduler)
     mmCounter.cleanup // cancel the refresh schedule
 
     def collectCounterSnapshot(): Histogram.Snapshot = mmCounter.collect(collectionContext)
diff --git a/kamon-core/src/test/scala/kamon/testkit/BaseKamonSpec.scala b/kamon-core/src/test/scala/kamon/testkit/BaseKamonSpec.scala
index 9142ff16..eab6b754 100644
--- a/kamon-core/src/test/scala/kamon/testkit/BaseKamonSpec.scala
+++ b/kamon-core/src/test/scala/kamon/testkit/BaseKamonSpec.scala
@@ -22,29 +22,39 @@ import com.typesafe.config.{ Config, ConfigFactory }
 import kamon.Kamon
 import kamon.metric.{ SubscriptionsDispatcher, EntitySnapshot, MetricsExtensionImpl }
 import kamon.trace.TraceContext
+import kamon.util.LazyActorRef
 import org.scalatest.{ BeforeAndAfterAll, Matchers, WordSpecLike }
 
+import scala.reflect.ClassTag
+
 abstract class BaseKamonSpec(actorSystemName: String) extends TestKitBase with WordSpecLike with Matchers with ImplicitSender with BeforeAndAfterAll {
-  lazy val kamon = Kamon(actorSystemName, config)
-  lazy val collectionContext = kamon.metrics.buildDefaultCollectionContext
-  implicit lazy val system: ActorSystem = kamon.actorSystem
+  lazy val collectionContext = Kamon.metrics.buildDefaultCollectionContext
+  implicit lazy val system: ActorSystem = {
+    Kamon.start(config.withFallback(ConfigFactory.load()))
+    ActorSystem(actorSystemName, config)
+  }
 
   def config: Config =
-    ConfigFactory.load()
+    ConfigFactory.empty()
 
   def newContext(name: String): TraceContext =
-    kamon.tracer.newContext(name)
+    Kamon.tracer.newContext(name)
 
   def newContext(name: String, token: String): TraceContext =
-    kamon.tracer.newContext(name, token)
+    Kamon.tracer.newContext(name, token)
 
   def takeSnapshotOf(name: String, category: String): EntitySnapshot = {
-    val recorder = kamon.metrics.find(name, category).get
+    val recorder = Kamon.metrics.find(name, category).get
     recorder.collect(collectionContext)
   }
 
-  def flushSubscriptions(): Unit =
-    system.actorSelection("/user/kamon/subscriptions-dispatcher") ! SubscriptionsDispatcher.Tick
+  def flushSubscriptions(): Unit = {
+    val subscriptionsField = Kamon.metrics.getClass.getDeclaredField("_subscriptions")
+    subscriptionsField.setAccessible(true)
+    val subscriptions = subscriptionsField.get(Kamon.metrics).asInstanceOf[LazyActorRef]
+
+    subscriptions.tell(SubscriptionsDispatcher.Tick)
+  }
 
   override protected def afterAll(): Unit = system.shutdown()
 }
diff --git a/kamon-core/src/test/scala/kamon/trace/SimpleTraceSpec.scala b/kamon-core/src/test/scala/kamon/trace/SimpleTraceSpec.scala
index 0cb4ce34..1d270106 100644
--- a/kamon-core/src/test/scala/kamon/trace/SimpleTraceSpec.scala
+++ b/kamon-core/src/test/scala/kamon/trace/SimpleTraceSpec.scala
@@ -40,7 +40,7 @@ class SimpleTraceSpec extends BaseKamonSpec("simple-trace-spec") {
 
   "the simple tracing" should {
     "send a TraceInfo when the trace has finished and all segments are finished" in {
-      Kamon(Tracer)(system).subscribe(testActor)
+      Kamon.tracer.subscribe(testActor)
 
       TraceContext.withContext(newContext("simple-trace-without-segments")) {
         TraceContext.currentContext.startSegment("segment-one", "test-segment", "test").finish()
@@ -49,7 +49,7 @@ class SimpleTraceSpec extends BaseKamonSpec("simple-trace-spec") {
       }
 
       val traceInfo = expectMsgType[TraceInfo]
-      Kamon(Tracer)(system).unsubscribe(testActor)
+      Kamon.tracer.unsubscribe(testActor)
 
       traceInfo.name should be("simple-trace-without-segments")
       traceInfo.segments.size should be(2)
@@ -58,7 +58,7 @@ class SimpleTraceSpec extends BaseKamonSpec("simple-trace-spec") {
     }
 
     "incubate the tracing context if there are open segments after finishing" in {
-      Kamon(Tracer)(system).subscribe(testActor)
+      Kamon.tracer.subscribe(testActor)
 
       val secondSegment = TraceContext.withContext(newContext("simple-trace-without-segments")) {
         TraceContext.currentContext.startSegment("segment-one", "test-segment", "test").finish()
@@ -72,7 +72,7 @@ class SimpleTraceSpec extends BaseKamonSpec("simple-trace-spec") {
 
       within(10 seconds) {
         val traceInfo = expectMsgType[TraceInfo]
-        Kamon(Tracer)(system).unsubscribe(testActor)
+        Kamon.tracer.unsubscribe(testActor)
 
         traceInfo.name should be("simple-trace-without-segments")
         traceInfo.segments.size should be(2)
-- 
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