sdk-metrics: add SdkObservableGauge

sdk/metrics/src/main/scala/org/typelevel/otel4s/sdk/metrics/SdkObservableGauge.scala

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2024 Typelevel
+ *
+ * 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 org.typelevel.otel4s.sdk.metrics
+
+import cats.data.NonEmptyList
+import cats.effect.Clock
+import cats.effect.MonadCancelThrow
+import cats.effect.Resource
+import cats.effect.std.Console
+import cats.syntax.flatMap._
+import cats.syntax.foldable._
+import cats.syntax.functor._
+import org.typelevel.ci.CIString
+import org.typelevel.otel4s.metrics.Measurement
+import org.typelevel.otel4s.metrics.MeasurementValue
+import org.typelevel.otel4s.metrics.ObservableGauge
+import org.typelevel.otel4s.metrics.ObservableMeasurement
+import org.typelevel.otel4s.sdk.context.AskContext
+import org.typelevel.otel4s.sdk.metrics.internal.CallbackRegistration
+import org.typelevel.otel4s.sdk.metrics.internal.InstrumentDescriptor
+import org.typelevel.otel4s.sdk.metrics.internal.MeterSharedState
+
+/** An asynchronous instrument that reports non-additive values.
+  *
+  * @see
+  *   [[https://opentelemetry.io/docs/specs/otel/metrics/api/#asynchronous-gauge]]
+  */
+private object SdkObservableGauge {
+
+  final case class Builder[
+      F[_]: MonadCancelThrow: Clock: Console: AskContext,
+      A: MeasurementValue
+  ](
+      name: String,
+      sharedState: MeterSharedState[F],
+      unit: Option[String] = None,
+      description: Option[String] = None
+  ) extends ObservableGauge.Builder[F, A] {
+
+    def withUnit(unit: String): ObservableGauge.Builder[F, A] =
+      copy(unit = Some(unit))
+
+    def withDescription(description: String): ObservableGauge.Builder[F, A] =
+      copy(description = Some(description))
+
+    def createWithCallback(
+        cb: ObservableMeasurement[F, A] => F[Unit]
+    ): Resource[F, ObservableGauge] = {
+      val descriptor = makeDescriptor
+
+      val makeCallbackRegistration: F[CallbackRegistration[F]] =
+        MeasurementValue[A] match {
+          case MeasurementValue.LongMeasurementValue(cast) =>
+            sharedState
+              .registerObservableMeasurement[Long](descriptor)
+              .map { observable =>
+                val runnable = cb { (value, attributes) =>
+                  observable.record(cast(value), attributes)
+                }
+
+                new CallbackRegistration[F](
+                  NonEmptyList.one(observable),
+                  runnable
+                )
+              }
+
+          case MeasurementValue.DoubleMeasurementValue(cast) =>
+            sharedState
+              .registerObservableMeasurement[Double](descriptor)
+              .map { observable =>
+                val runnable = cb { (value, attributes) =>
+                  observable.record(cast(value), attributes)
+                }
+
+                new CallbackRegistration[F](
+                  NonEmptyList.one(observable),
+                  runnable
+                )
+              }
+        }
+
+      for {
+        cr <- Resource.eval(makeCallbackRegistration)
+        _ <- sharedState.withCallback(cr)
+      } yield new ObservableGauge {}
+    }
+
+    def create(
+        measurements: F[Iterable[Measurement[A]]]
+    ): Resource[F, ObservableGauge] =
+      createWithCallback { cb =>
+        for {
+          m <- measurements
+          _ <- m.toVector.traverse_(m => cb.record(m.value, m.attributes))
+        } yield ()
+      }
+
+    def createObserver: F[ObservableMeasurement[F, A]] = {
+      val descriptor = makeDescriptor
+
+      MeasurementValue[A] match {
+        case MeasurementValue.LongMeasurementValue(cast) =>
+          sharedState
+            .registerObservableMeasurement[Long](descriptor)
+            .map { observable => (value, attributes) =>
+              observable.record(cast(value), attributes)
+            }
+
+        case MeasurementValue.DoubleMeasurementValue(cast) =>
+          sharedState
+            .registerObservableMeasurement[Double](descriptor)
+            .map { observable => (value, attributes) =>
+              observable.record(cast(value), attributes)
+            }
+      }
+    }
+
+    private def makeDescriptor: InstrumentDescriptor.Asynchronous =
+      InstrumentDescriptor.asynchronous(
+        name = CIString(name),
+        description = description,
+        unit = unit,
+        instrumentType = InstrumentType.ObservableGauge
+      )
+  }
+
+}

sdk/metrics/src/test/scala/org/typelevel/otel4s/sdk/metrics/SdkObservableGaugeSuite.scala

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2024 Typelevel
+ *
+ * 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 org.typelevel.otel4s.sdk.metrics
+
+import cats.effect.IO
+import cats.effect.std.Random
+import cats.mtl.Ask
+import munit.CatsEffectSuite
+import munit.ScalaCheckEffectSuite
+import org.scalacheck.Gen
+import org.scalacheck.effect.PropF
+import org.typelevel.otel4s.metrics.Measurement
+import org.typelevel.otel4s.metrics.MeasurementValue
+import org.typelevel.otel4s.sdk.TelemetryResource
+import org.typelevel.otel4s.sdk.common.InstrumentationScope
+import org.typelevel.otel4s.sdk.context.Context
+import org.typelevel.otel4s.sdk.metrics.data.MetricData
+import org.typelevel.otel4s.sdk.metrics.data.MetricPoints
+import org.typelevel.otel4s.sdk.metrics.exemplar.ExemplarFilter
+import org.typelevel.otel4s.sdk.metrics.exemplar.TraceContextLookup
+import org.typelevel.otel4s.sdk.metrics.exporter.AggregationTemporalitySelector
+import org.typelevel.otel4s.sdk.metrics.exporter.InMemoryMetricReader
+import org.typelevel.otel4s.sdk.metrics.exporter.MetricProducer
+import org.typelevel.otel4s.sdk.metrics.internal.MeterSharedState
+import org.typelevel.otel4s.sdk.metrics.internal.exporter.RegisteredReader
+import org.typelevel.otel4s.sdk.metrics.scalacheck.Gens
+import org.typelevel.otel4s.sdk.metrics.test.PointDataUtils
+import org.typelevel.otel4s.sdk.metrics.view.ViewRegistry
+
+import scala.concurrent.duration.FiniteDuration
+
+class SdkObservableGaugeSuite
+    extends CatsEffectSuite
+    with ScalaCheckEffectSuite {
+
+  private implicit val askContext: Ask[IO, Context] = Ask.const(Context.root)
+
+  test("record values") {
+    PropF.forAllF(
+      Gens.telemetryResource,
+      Gens.instrumentationScope,
+      Gens.timeWindow,
+      Gens.attributes,
+      Gens.nonEmptyString,
+      Gen.option(Gen.alphaNumStr),
+      Gen.option(Gen.alphaNumStr),
+      Gen.either(Gen.long, Gen.double)
+    ) { (resource, scope, window, attrs, name, unit, description, value) =>
+      def test[A: MeasurementValue](value: A): IO[Unit] = {
+        val expected = MetricData(
+          resource,
+          scope,
+          name,
+          description,
+          unit,
+          MetricPoints.gauge(
+            points = PointDataUtils.toNumberPoints(
+              Vector(value),
+              attrs,
+              window
+            )
+          )
+        )
+
+        for {
+          reader <- createReader(window.start)
+          state <- createState(resource, scope, reader, window.start)
+
+          _ <- SdkObservableGauge
+            .Builder[IO, A](name, state, unit, description)
+            .createWithCallback(cb => cb.record(value, attrs))
+            .surround(
+              state.collectAll(reader, window.end)
+            )
+            .assertEquals(Vector(expected))
+
+          _ <- SdkObservableGauge
+            .Builder[IO, A](name, state, unit, description)
+            .create(IO.pure(Vector(Measurement(value, attrs))))
+            .surround(
+              state.collectAll(reader, window.end)
+            )
+            .assertEquals(Vector(expected))
+        } yield ()
+      }
+
+      value match {
+        case Left(long)    => test[Long](long)
+        case Right(double) => test[Double](double)
+      }
+    }
+  }
+
+  private def createReader(start: FiniteDuration): IO[RegisteredReader[IO]] = {
+    val inMemory = new InMemoryMetricReader[IO](
+      emptyProducer,
+      AggregationTemporalitySelector.alwaysCumulative
+    )
+
+    RegisteredReader.create(start, inMemory)
+  }
+
+  private def createState(
+      resource: TelemetryResource,
+      scope: InstrumentationScope,
+      reader: RegisteredReader[IO],
+      start: FiniteDuration
+  ): IO[MeterSharedState[IO]] =
+    Random.scalaUtilRandom[IO].flatMap { implicit R: Random[IO] =>
+      MeterSharedState.create[IO](
+        resource,
+        scope,
+        start,
+        ExemplarFilter.alwaysOff,
+        TraceContextLookup.noop,
+        ViewRegistry(Vector.empty),
+        Vector(reader)
+      )
+    }
+
+  private def emptyProducer: MetricProducer[IO] =
+    new MetricProducer[IO] {
+      def produce: IO[Vector[MetricData]] = IO.pure(Vector.empty)
+    }
+
+}