Implement Micrometer module for Prometheus metrics

build.sbt

@@ -33,6 +33,8 @@ lazy val root = project
     micrometer,
     micrometerJmx,
     micrometerJmxPureConfig,
+    micrometerPrometheus,
+    micrometerPrometheusPureConfig,
     micrometerStatsD,
     micrometerStatsDPureConfig,
     monixCatnap,
@@ -394,6 +396,24 @@ lazy val micrometerJmxPureConfig = project
     libraryDependencies += Dependencies.pureConfig
   )
 
+lazy val micrometerPrometheus = project
+  .in(file("micrometer-prometheus"))
+  .dependsOn(micrometer)
+  .settings(BuildSettings.common)
+  .settings(
+    name := "sst-micrometer-prometheus",
+    libraryDependencies += Dependencies.micrometerPrometheus
+  )
+
+lazy val micrometerPrometheusPureConfig = project
+  .in(file("micrometer-prometheus-pureconfig"))
+  .dependsOn(micrometerPrometheus)
+  .settings(BuildSettings.common)
+  .settings(
+    name := "sst-micrometer-prometheus-pureconfig",
+    libraryDependencies += Dependencies.pureConfig
+  )
+
 lazy val micrometerStatsD = project
   .in(file("micrometer-statsd"))
   .dependsOn(micrometer)

micrometer-prometheus-pureconfig/src/main/scala/com/avast/sst/micrometer/prometheus/pureconfig/ConfigReaders.scala

@@ -0,0 +1,14 @@
+package com.avast.sst.micrometer.prometheus.pureconfig
+
+import com.avast.sst.micrometer.prometheus.MicrometerPrometheusConfig
+import pureconfig.ConfigReader
+import pureconfig.generic.ProductHint
+import pureconfig.generic.semiauto.deriveReader
+
+trait ConfigReaders {
+
+  implicit protected def hint[T]: ProductHint[T] = ProductHint.default
+
+  implicit val micrometerPrometheusConfigReader: ConfigReader[MicrometerPrometheusConfig] = deriveReader
+
+}

micrometer-prometheus-pureconfig/src/main/scala/com/avast/sst/micrometer/prometheus/pureconfig/implicits.scala

@@ -0,0 +1,20 @@
+package com.avast.sst.micrometer.prometheus.pureconfig
+
+import pureconfig.ConfigFieldMapping
+import pureconfig.generic.ProductHint
+
+/** Contains [[pureconfig.ConfigReader]] instances with default "kebab-case" naming convention. */
+object implicits extends ConfigReaders {
+
+  /** Contains [[pureconfig.ConfigReader]] instances with "kebab-case" naming convention.
+    *
+    * This is alias for the default `implicits._` import.
+    */
+  object KebabCase extends ConfigReaders
+
+  /** Contains [[pureconfig.ConfigReader]] instances with "camelCase" naming convention. */
+  object CamelCase extends ConfigReaders {
+    implicit override protected def hint[T]: ProductHint[T] = ProductHint(ConfigFieldMapping(pureconfig.CamelCase, pureconfig.CamelCase))
+  }
+
+}

micrometer-prometheus/src/main/scala/com/avast/sst/micrometer/prometheus/MicrometerPrometheusConfig.scala

@@ -0,0 +1,14 @@
+package com.avast.sst.micrometer.prometheus
+
+import io.micrometer.prometheus.HistogramFlavor
+
+import java.util.concurrent.TimeUnit
+import scala.concurrent.duration.Duration
+
+final case class MicrometerPrometheusConfig(
+    step: Duration = Duration(1, TimeUnit.MINUTES),
+    prefix: String = "",
+    descriptions: Boolean = true,
+    histogramFlavor: HistogramFlavor = HistogramFlavor.Prometheus,
+    commonTags: Map[String, String] = Map.empty
+)

micrometer-prometheus/src/main/scala/com/avast/sst/micrometer/prometheus/MicrometerPrometheusModule.scala

@@ -0,0 +1,55 @@
+package com.avast.sst.micrometer.prometheus
+
+import cats.effect.{Blocker, ContextShift, Resource, Sync}
+import com.avast.sst.micrometer.PrefixMeterFilter
+import io.micrometer.core.instrument.config.{MeterFilter, NamingConvention}
+import io.micrometer.prometheus.{HistogramFlavor, PrometheusConfig, PrometheusMeterRegistry}
+
+import java.time.Duration
+
+object MicrometerPrometheusModule {
+
+  /** Makes configured [[io.micrometer.prometheus.PrometheusMeterRegistry]]. */
+  def make[F[_]: Sync: ContextShift](
+      config: MicrometerPrometheusConfig,
+      blocker: Blocker,
+      namingConvention: Option[NamingConvention] = None,
+      meterFilter: Option[MeterFilter] = None
+  ): Resource[F, PrometheusMeterRegistry] = {
+    Resource
+      .make {
+        Sync[F].delay {
+          val registry = new PrometheusMeterRegistry(new CustomPrometheusConfig(config))
+
+          namingConvention.foreach(registry.config().namingConvention)
+
+          if (config.prefix.nonEmpty) {
+            registry.config().meterFilter(new PrefixMeterFilter(config.prefix))
+          }
+
+          meterFilter.foreach(registry.config().meterFilter)
+
+          val preprocessedTags = config.commonTags.foldRight(List.empty[String]) { case (tag, acc) =>
+            tag._1 :: tag._2 :: acc
+          }
+          registry.config().commonTags(preprocessedTags: _*)
+
+          registry
+        }
+      }(registry => blocker.delay(registry.close()))
+  }
+
+  private class CustomPrometheusConfig(c: MicrometerPrometheusConfig) extends PrometheusConfig {
+
+    override val step: Duration = java.time.Duration.ofMillis(c.step.toMillis)
+    override val prefix: String = c.prefix
+    override val descriptions: Boolean = c.descriptions
+    override val histogramFlavor: HistogramFlavor = c.histogramFlavor
+
+    // the method is @Nullable and we don't need to implement it here
+    @SuppressWarnings(Array("scalafix:DisableSyntax.null"))
+    override def get(key: String): String = null
+
+  }
+
+}

project/Dependencies.scala

@@ -24,6 +24,7 @@ object Dependencies {
   val micrometerCore = "io.micrometer" % "micrometer-core" % Versions.micrometerCore
   val micrometerJmx = "io.micrometer" % "micrometer-registry-jmx" % Versions.micrometerJmx
   val micrometerStatsD = "io.micrometer" % "micrometer-registry-statsd" % Versions.micrometerStatsD
+  val micrometerPrometheus = "io.micrometer" % "micrometer-registry-prometheus" % Versions.micrometerPrometheus
   val monixCatnap = "io.monix" %% "monix-catnap" % Versions.monix
   val monixEval = "io.monix" %% "monix-eval" % Versions.monix
   val postgresql = "org.postgresql" % "postgresql" % "42.3.0"
@@ -49,6 +50,7 @@ object Dependencies {
     val micrometerCore = "1.7.5"
     val micrometerJmx = "1.7.5"
     val micrometerStatsD = "1.7.5"
+    val micrometerPrometheus = "1.7.5"
     val monix = "3.4.0"
 
   }