sdk-metrics: add ExemplarFilterAutoConfigure

sdk/metrics/src/main/scala/org/typelevel/otel4s/sdk/metrics/autoconfigure/ExemplarFilterAutoConfigure.scala

@@ -0,0 +1,129 @@
+/*
+ * 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.autoconfigure
+
+import cats.MonadThrow
+import cats.effect.Resource
+import org.typelevel.otel4s.sdk.autoconfigure.AutoConfigure
+import org.typelevel.otel4s.sdk.autoconfigure.Config
+import org.typelevel.otel4s.sdk.autoconfigure.ConfigurationError
+import org.typelevel.otel4s.sdk.metrics.exemplar.ExemplarFilter
+import org.typelevel.otel4s.sdk.metrics.exemplar.TraceContextLookup
+
+import java.util.Locale
+
+/** Autoconfigures an [[ExemplarFilter]].
+  *
+  * The configuration options:
+  * {{{
+  * | System property              | Environment variable         | Description                                           |
+  * |------------------------------|------------------------------|-------------------------------------------------------|
+  * | otel.metrics.exemplar.filter | OTEL_METRICS_EXEMPLAR_FILTER | The exemplar filter to use. Default is `trace_based`. |
+  * }}}
+  *
+  * The following options for `otel.metrics.exemplar.filter` are supported:
+  *   - `always_on` - [[ExemplarFilter.alwaysOn]]
+  *   - `always_off` - [[ExemplarFilter.alwaysOff]]
+  *   - `trace_based` - [[ExemplarFilter.traceBased]]
+  *
+  * @see
+  *   [[https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#exemplars]]
+  */
+private final class ExemplarFilterAutoConfigure[F[_]: MonadThrow](
+    lookup: TraceContextLookup
+) extends AutoConfigure.WithHint[F, ExemplarFilter](
+      "ExemplarFilter",
+      ExemplarFilterAutoConfigure.ConfigKeys.All
+    ) {
+
+  import ExemplarFilterAutoConfigure.ConfigKeys
+  import ExemplarFilterAutoConfigure.Defaults
+
+  private val configurers: Set[AutoConfigure.Named[F, ExemplarFilter]] = Set(
+    AutoConfigure.Named.const("always_on", ExemplarFilter.alwaysOn),
+    AutoConfigure.Named.const("always_off", ExemplarFilter.alwaysOff),
+    AutoConfigure.Named.const("trace_based", ExemplarFilter.traceBased(lookup))
+  )
+
+  protected def fromConfig(config: Config): Resource[F, ExemplarFilter] = {
+    val exemplarFilterValue = config
+      .getOrElse(ConfigKeys.ExemplarFilter, Defaults.ExemplarFilter)
+      .map(_.toLowerCase)
+
+    exemplarFilterValue match {
+      case Right(name) =>
+        configurers.find(_.name == name) match {
+          case Some(configure) =>
+            configure.configure(config)
+
+          case None =>
+            Resource.raiseError(
+              ConfigurationError.unrecognized(
+                ConfigKeys.ExemplarFilter.name,
+                name,
+                configurers.map(_.name)
+              ): Throwable
+            )
+        }
+
+      case Left(error) =>
+        Resource.raiseError(error: Throwable)
+    }
+  }
+
+}
+
+private[sdk] object ExemplarFilterAutoConfigure {
+
+  private object ConfigKeys {
+    val ExemplarFilter: Config.Key[String] =
+      Config.Key("otel.metrics.exemplar.filter")
+
+    val All: Set[Config.Key[_]] = Set(ExemplarFilter)
+  }
+
+  private object Defaults {
+    val ExemplarFilter: String = "trace_based"
+  }
+
+  /** Autoconfigures an [[ExemplarFilter]].
+    *
+    * The configuration options:
+    * {{{
+    * | System property              | Environment variable         | Description                                           |
+    * |------------------------------|------------------------------|-------------------------------------------------------|
+    * | otel.metrics.exemplar.filter | OTEL_METRICS_EXEMPLAR_FILTER | The exemplar filter to use. Default is `trace_based`. |
+    * }}}
+    *
+    * The following options for `otel.metrics.exemplar.filter` are supported:
+    *   - `always_on` - [[ExemplarFilter.alwaysOn]]
+    *   - `always_off` - [[ExemplarFilter.alwaysOff]]
+    *   - `trace_based` - [[ExemplarFilter.traceBased]]
+    *
+    * @see
+    *   [[https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#exemplars]]
+    *
+    * @param traceContextLookup
+    *   used by the exemplar reservoir to extract tracing information from the
+    *   context
+    */
+  def apply[F[_]: MonadThrow](
+      traceContextLookup: TraceContextLookup
+  ): AutoConfigure[F, ExemplarFilter] =
+    new ExemplarFilterAutoConfigure[F](traceContextLookup)
+
+}

sdk/metrics/src/main/scala/org/typelevel/otel4s/sdk/metrics/exemplar/ExemplarFilter.scala

@@ -38,8 +38,8 @@ sealed trait ExemplarFilter {
 }
 
 object ExemplarFilter {
-  private val AlwaysOn = new Const(decision = true)
-  private val AlwaysOff = new Const(decision = false)
+  private val AlwaysOn = Const(decision = true)
+  private val AlwaysOff = Const(decision = false)
 
   /** A filter which makes all measurements eligible for being an exemplar.
     */
@@ -53,9 +53,9 @@ object ExemplarFilter {
     * that is being sampled.
     */
   def traceBased(lookup: TraceContextLookup): ExemplarFilter =
-    new TraceBased(lookup)
+    TraceBased(lookup)
 
-  private final class Const(decision: Boolean) extends ExemplarFilter {
+  private final case class Const(decision: Boolean) extends ExemplarFilter {
     def shouldSample[A: MeasurementValue](
         value: A,
         attributes: Attributes,
@@ -64,7 +64,7 @@ object ExemplarFilter {
       decision
   }
 
-  private final class TraceBased(
+  private final case class TraceBased(
       lookup: TraceContextLookup
   ) extends ExemplarFilter {
     def shouldSample[A: MeasurementValue](

sdk/metrics/src/test/scala/org/typelevel/otel4s/sdk/metrics/autoconfigure/ExemplarFilterAutoConfigureSuite.scala

@@ -0,0 +1,91 @@
+/*
+ * 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.autoconfigure
+
+import cats.effect.IO
+import cats.syntax.either._
+import munit.CatsEffectSuite
+import org.typelevel.otel4s.sdk.autoconfigure.Config
+import org.typelevel.otel4s.sdk.metrics.exemplar.ExemplarFilter
+import org.typelevel.otel4s.sdk.metrics.exemplar.TraceContextLookup
+
+class ExemplarFilterAutoConfigureSuite extends CatsEffectSuite {
+
+  private val lookup =
+    TraceContextLookup.noop
+
+  private val configurer =
+    ExemplarFilterAutoConfigure[IO](lookup)
+
+  test("load from an empty config - load default") {
+    val config = Config(Map.empty, Map.empty, Map.empty)
+    configurer.configure(config).use { filter =>
+      IO(assertEquals(filter, ExemplarFilter.traceBased(lookup)))
+    }
+  }
+
+  test("load from the config (empty string) - load default") {
+    val props = Map("otel.metrics.exemplar.filter" -> "")
+    val config = Config(props, Map.empty, Map.empty)
+    configurer.configure(config).use { filter =>
+      IO(assertEquals(filter, ExemplarFilter.traceBased(lookup)))
+    }
+  }
+
+  test("load from the config - always_on") {
+    val props = Map("otel.metrics.exemplar.filter" -> "always_on")
+    val config = Config(props, Map.empty, Map.empty)
+    configurer.configure(config).use { filter =>
+      IO(assertEquals(filter, ExemplarFilter.alwaysOn))
+    }
+  }
+
+  test("load from the config - always_off") {
+    val props = Map("otel.metrics.exemplar.filter" -> "always_off")
+    val config = Config(props, Map.empty, Map.empty)
+    configurer.configure(config).use { filter =>
+      IO(assertEquals(filter, ExemplarFilter.alwaysOff))
+    }
+  }
+
+  test("load from the config - trace_based") {
+    val props = Map("otel.metrics.exemplar.filter" -> "trace_based")
+    val config = Config(props, Map.empty, Map.empty)
+    configurer.configure(config).use { filter =>
+      IO(assertEquals(filter, ExemplarFilter.traceBased(lookup)))
+    }
+  }
+
+  test("load from the config - unknown filter - fail") {
+    val props = Map("otel.metrics.exemplar.filter" -> "some-filter")
+    val config = Config(props, Map.empty, Map.empty)
+
+    configurer
+      .configure(config)
+      .use_
+      .attempt
+      .map(_.leftMap(_.getMessage))
+      .assertEquals(
+        Left(
+          """Cannot autoconfigure [ExemplarFilter].
+            |Cause: Unrecognized value for [otel.metrics.exemplar.filter]: some-filter. Supported options [always_on, always_off, trace_based].
+            |Config:
+            |1) `otel.metrics.exemplar.filter` - some-filter""".stripMargin
+        )
+      )
+  }
+}

sdk/trace/src/test/scala/org/typelevel/otel4s/sdk/trace/autoconfigure/SamplerAutoConfigureSuite.scala

@@ -59,10 +59,10 @@ class SamplerAutoConfigureSuite extends CatsEffectSuite {
   }
 
   test("load from the config - always_off") {
-    val props = Map("otel.traces.sampler" -> "always_on")
+    val props = Map("otel.traces.sampler" -> "always_off")
     val config = Config(props, Map.empty, Map.empty)
     SamplerAutoConfigure[IO](Set.empty).configure(config).use { sampler =>
-      IO(assertEquals(sampler, Sampler.AlwaysOn))
+      IO(assertEquals(sampler, Sampler.AlwaysOff))
     }
   }