From ba35b9859a342bf9d6ceb12e169333f3b68f8b05 Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Tue, 18 Jul 2017 09:10:59 +0200
Subject: use "probability" instead of "chance" terms for the random sampler

---
 kamon-core/src/main/resources/reference.conf        |  8 ++++----
 kamon-core/src/main/scala/kamon/trace/Sampler.scala | 20 ++++++++++----------
 kamon-core/src/main/scala/kamon/trace/Tracer.scala  |  8 ++++----
 3 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/kamon-core/src/main/resources/reference.conf b/kamon-core/src/main/resources/reference.conf
index 6ad06325..06da8e18 100644
--- a/kamon-core/src/main/resources/reference.conf
+++ b/kamon-core/src/main/resources/reference.conf
@@ -88,17 +88,17 @@ kamon {
     # Configures a sample that decides which traces should be reported to the trace backends. The possible values are:
     #   - always: report all traces.
     #   - never:  don't report any trace.
-    #   - random: use the random tracer.
+    #   - random: randomly decide using the probability defined in the random-sampler.probability setting.
     #
     sampler = "random"
 
     # The random sampler uses the "chance" setting and a random number to take a decision, if the random number is
     # on the upper (chance * 100) percent of the number spectrum the trace will be sampled. E.g. a chance of 0.01 will
     # hint that 1% of all traces should be reported.
-    sampler-random {
+    random-sampler {
 
-      # Chance of a span being sampled. Must be a value between 0 and 1.
-      chance = 0.01
+      # Probability of a span being sampled. Must be a value between 0 and 1.
+      probability = 0.01
     }
   }
 
diff --git a/kamon-core/src/main/scala/kamon/trace/Sampler.scala b/kamon-core/src/main/scala/kamon/trace/Sampler.scala
index f478bbd1..e2aefe22 100644
--- a/kamon-core/src/main/scala/kamon/trace/Sampler.scala
+++ b/kamon-core/src/main/scala/kamon/trace/Sampler.scala
@@ -23,15 +23,15 @@ trait Sampler {
 }
 
 object Sampler {
-  val always = new Constant(SamplingDecision.Sample)
-  val never = new Constant(SamplingDecision.DoNotSample)
+  val Always = new Constant(SamplingDecision.Sample)
+  val Never = new Constant(SamplingDecision.DoNotSample)
 
-  def random(chance: Double): Sampler = {
-    assert(chance >= 0D && chance <= 1.0D, "Change should be >= 0 and <= 1.0")
+  def random(probability: Double): Sampler = {
+    assert(probability >= 0D && probability <= 1.0D, "The probability should be >= 0 and <= 1.0")
 
-    chance match {
-      case 0D       => never
-      case 1.0D     => always
+    probability match {
+      case 0D       => Never
+      case 1.0D     => Always
       case anyOther => new Random(anyOther)
     }
   }
@@ -43,8 +43,8 @@ object Sampler {
       s"Sampler.Constant(decision = $decision)"
   }
 
-  class Random(chance: Double) extends Sampler {
-    val upperBoundary = Long.MaxValue * chance
+  class Random(probability: Double) extends Sampler {
+    val upperBoundary = Long.MaxValue * probability
     val lowerBoundary = -upperBoundary
 
     override def decide(operationName: String, builderTags: Map[String, String]): SamplingDecision = {
@@ -53,6 +53,6 @@ object Sampler {
     }
 
     override def toString: String =
-      s"Sampler.Random(chance = $chance)"
+      s"Sampler.Random(probability = $probability)"
   }
 }
diff --git a/kamon-core/src/main/scala/kamon/trace/Tracer.scala b/kamon-core/src/main/scala/kamon/trace/Tracer.scala
index ecc690af..85d02c8d 100644
--- a/kamon-core/src/main/scala/kamon/trace/Tracer.scala
+++ b/kamon-core/src/main/scala/kamon/trace/Tracer.scala
@@ -51,7 +51,7 @@ object Tracer {
 
     private[Tracer] val tracerMetrics = new TracerMetrics(metrics)
     @volatile private[Tracer] var joinRemoteSpansWithSameID: Boolean = false
-    @volatile private[Tracer] var configuredSampler: Sampler = Sampler.never
+    @volatile private[Tracer] var configuredSampler: Sampler = Sampler.Never
     @volatile private[Tracer] var identityProvider: IdentityProvider = IdentityProvider.Default()
     @volatile private[Tracer] var textMapSpanContextCodec: SpanContextCodec[TextMap] = SpanContextCodec.ExtendedB3(identityProvider)
     @volatile private[Tracer] var httpHeaderSpanContextCodec: SpanContextCodec[TextMap] = SpanContextCodec.ExtendedB3(identityProvider)
@@ -99,9 +99,9 @@ object Tracer {
       val traceConfig = config.getConfig("kamon.trace")
 
       configuredSampler = traceConfig.getString("sampler") match {
-        case "always" => Sampler.always
-        case "never"  => Sampler.never
-        case "random" => Sampler.random(traceConfig.getDouble("sampler-random.chance"))
+        case "always" => Sampler.Always
+        case "never"  => Sampler.Never
+        case "random" => Sampler.random(traceConfig.getDouble("random-sampler.probability"))
         case other    => sys.error(s"Unexpected sampler name $other.")
       }
     }
-- 
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