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/* =========================================================================================
* Copyright © 2013-2017 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
import java.util.concurrent.ThreadLocalRandom
import kamon.trace.SpanContext.SamplingDecision
trait Sampler {
def decide(operationName: String, builderTags: Map[String, Span.TagValue]): SamplingDecision
}
object Sampler {
val Always = new Constant(SamplingDecision.Sample)
val Never = new Constant(SamplingDecision.DoNotSample)
def random(probability: Double): Sampler = {
assert(probability >= 0D && probability <= 1.0D, "The probability should be >= 0 and <= 1.0")
probability match {
case 0D => Never
case 1.0D => Always
case anyOther => new Random(anyOther)
}
}
class Constant(decision: SamplingDecision) extends Sampler {
override def decide(operationName: String, builderTags: Map[String, Span.TagValue]): SamplingDecision = decision
override def toString: String =
s"Sampler.Constant(decision = $decision)"
}
class Random(probability: Double) extends Sampler {
val upperBoundary = Long.MaxValue * probability
val lowerBoundary = -upperBoundary
override def decide(operationName: String, builderTags: Map[String, Span.TagValue]): SamplingDecision = {
val random = ThreadLocalRandom.current().nextLong()
if(random >= lowerBoundary && random <= upperBoundary) SamplingDecision.Sample else SamplingDecision.DoNotSample
}
override def toString: String =
s"Sampler.Random(probability = $probability)"
}
}
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