Instrumentation Examples

The trait below is used in the ZIO Metrics sample application just to show how the individual aspects can be configured and used.

Please refer to StatsD and Prometheus to see how the captured metrics can be visualized in the supported back ends.

trait InstrumentedSample {

  // Create a gauge, it can be applied to effects yielding a Double
  val aspGauge1 = Metric.gauge("gauge1")

  val aspGauge2 = Metric.gauge("gauge2")

  // Create a histogram with 12 buckets: 0..100 in steps of 10, Infinite
  // It also can be applied to effects yielding a Double
  val aspHistogram =
    Metric.histogram("myHistogram", MetricKeyType.Histogram.Boundaries.linear(0.0d, 10.0d, 11))

  // Create a summary that can hold 100 samples, the max age of the samples is 1 day.
  // The summary should report th 10%, 50% and 90% Quantile
  // It can be applied to effects yielding an Int
  val aspSummary =
    Metric.summary("mySummary", 1.day, 100, 0.03d, Chunk(0.1, 0.5, 0.9)).contramap[Int](_.toDouble)

  // Create a Set to observe the occurrences of unique Strings
  // It can be applied to effects yielding a String
  val aspSet = Metric.frequency("mySet")

  // Create a counter applicable to any effect
  val aspCountAll = Metric.counter("countAll").contramap[Any](_ => 1L)

  private lazy val gaugeSomething = for {
    _ <- Random.nextDoubleBetween(0.0d, 100.0d) @@ aspGauge1 @@ aspCountAll
    _ <- Random.nextDoubleBetween(-50d, 50d) @@ aspGauge2 @@ aspCountAll
  } yield ()

  // Just record something into a histogram
  private lazy val observeNumbers = for {
    _ <- Random.nextDoubleBetween(0.0d, 120.0d) @@ aspHistogram @@ aspCountAll
    _ <- Random.nextIntBetween(100, 500) @@ aspSummary @@ aspCountAll
  } yield ()

  // Observe Strings in order to capture unique values
  private lazy val observeKey = for {
    _ <- Random.nextIntBetween(10, 20).map(v => s"myKey-$v") @@ aspSet @@ aspCountAll
  } yield ()

  def program: ZIO[Any, Nothing, Unit] = for {
    _ <- gaugeSomething.schedule(Schedule.spaced(200.millis)).forkDaemon
    _ <- observeNumbers.schedule(Schedule.spaced(150.millis)).forkDaemon
    _ <- observeKey.schedule(Schedule.spaced(300.millis)).forkDaemon
  } yield ()
}