102 lines
3.4 KiB
Scala
102 lines
3.4 KiB
Scala
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/**
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* Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
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*/
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package akka.cluster.metrics
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import language.postfixOps
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import scala.concurrent.duration._
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import akka.testkit.{ LongRunningTest, AkkaSpec }
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import scala.concurrent.forkjoin.ThreadLocalRandom
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@org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
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class EWMASpec extends AkkaSpec(MetricsConfig.defaultEnabled) with MetricsCollectorFactory {
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import system.dispatcher
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val collector = createMetricsCollector
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"DataStream" must {
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"calcualate same ewma for constant values" in {
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val ds = EWMA(value = 100.0, alpha = 0.18) :+
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100.0 :+ 100.0 :+ 100.0
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ds.value should be(100.0 +- 0.001)
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}
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"calcualate correct ewma for normal decay" in {
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val d0 = EWMA(value = 1000.0, alpha = 2.0 / (1 + 10))
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d0.value should be(1000.0 +- 0.01)
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val d1 = d0 :+ 10.0
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d1.value should be(820.0 +- 0.01)
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val d2 = d1 :+ 10.0
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d2.value should be(672.73 +- 0.01)
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val d3 = d2 :+ 10.0
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d3.value should be(552.23 +- 0.01)
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val d4 = d3 :+ 10.0
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d4.value should be(453.64 +- 0.01)
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val dn = (1 to 100).foldLeft(d0)((d, _) ⇒ d :+ 10.0)
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dn.value should be(10.0 +- 0.1)
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}
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"calculate ewma for alpha 1.0, max bias towards latest value" in {
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val d0 = EWMA(value = 100.0, alpha = 1.0)
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d0.value should be(100.0 +- 0.01)
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val d1 = d0 :+ 1.0
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d1.value should be(1.0 +- 0.01)
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val d2 = d1 :+ 57.0
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d2.value should be(57.0 +- 0.01)
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val d3 = d2 :+ 10.0
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d3.value should be(10.0 +- 0.01)
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}
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"calculate alpha from half-life and collect interval" in {
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// according to http://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
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val expectedAlpha = 0.1
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// alpha = 2.0 / (1 + N)
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val n = 19
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val halfLife = n.toDouble / 2.8854
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val collectInterval = 1.second
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val halfLifeDuration = (halfLife * 1000).millis
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EWMA.alpha(halfLifeDuration, collectInterval) should be(expectedAlpha +- 0.001)
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}
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"calculate sane alpha from short half-life" in {
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val alpha = EWMA.alpha(1.millis, 3.seconds)
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alpha should be <= (1.0)
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alpha should be >= (0.0)
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alpha should be(1.0 +- 0.001)
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}
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"calculate sane alpha from long half-life" in {
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val alpha = EWMA.alpha(1.day, 3.seconds)
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alpha should be <= (1.0)
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alpha should be >= (0.0)
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alpha should be(0.0 +- 0.001)
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}
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"calculate the ewma for multiple, variable, data streams" taggedAs LongRunningTest in {
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var streamingDataSet = Map.empty[String, Metric]
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var usedMemory = Array.empty[Byte]
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(1 to 50) foreach { _ ⇒
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// wait a while between each message to give the metrics a chance to change
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Thread.sleep(100)
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usedMemory = usedMemory ++ Array.fill(1024)(ThreadLocalRandom.current.nextInt(127).toByte)
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val changes = collector.sample.metrics.flatMap { latest ⇒
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streamingDataSet.get(latest.name) match {
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case None ⇒ Some(latest)
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case Some(previous) ⇒
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if (latest.isSmooth && latest.value != previous.value) {
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val updated = previous :+ latest
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updated.isSmooth should be(true)
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updated.smoothValue should not be (previous.smoothValue)
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Some(updated)
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} else None
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}
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}
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streamingDataSet ++= changes.map(m ⇒ m.name -> m)
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}
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}
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}
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}
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