Add gzip and deflate encoding to metrics serving (#141)

Author: RustedBones

build.sbt

@@ -1,3 +1,5 @@
+import com.typesafe.tools.mima.core.*
+
 // General info
 val username  = "RustedBones"
 val repo      = "pekko-http-metrics"
@@ -40,7 +42,14 @@ ThisBuild / tlFatalWarnings := true
 ThisBuild / tlJdkRelease    := Some(8)
 
 // mima
-ThisBuild / mimaBinaryIssueFilters ++= Seq()
+ThisBuild / mimaBinaryIssueFilters ++= Seq(
+  ProblemFilters.exclude[IncompatibleResultTypeProblem](
+    "fr.davit.pekko.http.metrics.core.scaladsl.server.HttpMetricsDirectives.metrics"
+  ),
+  ProblemFilters.exclude[DirectMissingMethodProblem](
+    "fr.davit.pekko.http.metrics.core.scaladsl.server.HttpMetricsDirectives.metrics"
+  )
+)
 
 lazy val `pekko-http-metrics` = (project in file("."))
   .aggregate(

core/src/main/scala/fr/davit/pekko/http/metrics/core/scaladsl/server/HttpMetricsDirectives.scala

@@ -20,12 +20,13 @@ import org.apache.pekko.http.scaladsl.marshalling.ToEntityMarshaller
 import org.apache.pekko.http.scaladsl.server.Directives._
 import org.apache.pekko.http.scaladsl.server.PathMatcher.{Matched, Unmatched}
 import org.apache.pekko.http.scaladsl.server.util.Tuple
-import org.apache.pekko.http.scaladsl.server.{Directive, Directive0, PathMatcher, StandardRoute}
+import org.apache.pekko.http.scaladsl.server.{Directive, Directive0, PathMatcher, Route}
 import fr.davit.pekko.http.metrics.core.{AttributeLabeler, HttpMetricsRegistry, PathLabeler}
 
 trait HttpMetricsDirectives {
 
-  def metrics[T <: HttpMetricsRegistry: ToEntityMarshaller](registry: T): StandardRoute = complete(registry)
+  def metrics[T <: HttpMetricsRegistry: ToEntityMarshaller](registry: T): Route =
+    encodeResponse(complete(registry))
 
   def metricsLabeled(labeler: AttributeLabeler, label: String): Directive0 =
     mapResponse(_.addAttribute(labeler.key, label))

core/src/test/scala/fr/davit/pekko/http/metrics/core/scaladsl/server/HttpMetricsDirectivesSpec.scala

@@ -16,18 +16,35 @@
 
 package fr.davit.pekko.http.metrics.core.scaladsl.server
 
-import org.apache.pekko.http.scaladsl.marshalling.PredefinedToEntityMarshallers._
+import fr.davit.pekko.http.metrics.core.AttributeLabeler
+import fr.davit.pekko.http.metrics.core.PathLabeler
+import fr.davit.pekko.http.metrics.core.TestRegistry
+import org.apache.pekko.http.scaladsl.marshalling.PredefinedToEntityMarshallers.*
+import org.apache.pekko.http.scaladsl.model.HttpResponse
 import org.apache.pekko.http.scaladsl.model.StatusCodes
-import org.apache.pekko.http.scaladsl.server.Directives._
+import org.apache.pekko.http.scaladsl.model.headers.HttpEncoding
+import org.apache.pekko.http.scaladsl.model.headers.HttpEncodings
+import org.apache.pekko.http.scaladsl.model.headers.`Accept-Encoding`
+import org.apache.pekko.http.scaladsl.model.headers.`Content-Encoding`
+import org.apache.pekko.http.scaladsl.server.Directives.*
 import org.apache.pekko.http.scaladsl.testkit.ScalatestRouteTest
-import fr.davit.pekko.http.metrics.core.{AttributeLabeler, PathLabeler, TestRegistry}
 import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.Matcher
 import org.scalatest.matchers.should.Matchers
+import org.apache.pekko.http.scaladsl.coding.Coders
+import org.apache.pekko.http.scaladsl.unmarshalling.Unmarshal
+import scala.concurrent.Await
+import scala.concurrent.duration.*
 
 class HttpMetricsDirectivesSpec extends AnyFlatSpec with Matchers with ScalatestRouteTest {
 
   import HttpMetricsDirectives._
 
+  def haveNoContentEncoding: Matcher[HttpResponse]                       =
+    be(None).compose { (_: HttpResponse).header[`Content-Encoding`] }
+  def haveContentEncoding(encoding: HttpEncoding): Matcher[HttpResponse] =
+    be(Some(`Content-Encoding`(encoding))).compose { (_: HttpResponse).header[`Content-Encoding`] }
+
   "HttpMetricsDirectives" should "expose the registry" in {
     implicit val marshaller = StringMarshaller.compose[TestRegistry](r => s"active: ${r.requestsActive.value()}")
     val registry            = new TestRegistry()
@@ -38,6 +55,29 @@ class HttpMetricsDirectivesSpec extends AnyFlatSpec with Matchers with Scalatest
     }
 
     Get("/metrics") ~> route ~> check {
+      response should haveNoContentEncoding
+      responseAs[String] shouldBe "active: 1"
+    }
+
+    // gzip
+    Get("/metrics") ~> `Accept-Encoding`(HttpEncodings.gzip) ~> route ~> check {
+      response should haveContentEncoding(HttpEncodings.gzip)
+      val decodedResponse = Coders.Gzip.decodeMessage(response)
+      val data            = Await.result(Unmarshal(decodedResponse).to[String], 1.second)
+      data shouldBe "active: 1"
+    }
+
+    // deflate
+    Get("/metrics") ~> `Accept-Encoding`(HttpEncodings.deflate) ~> route ~> check {
+      response should haveContentEncoding(HttpEncodings.deflate)
+      val decodedResponse = Coders.Deflate.decodeMessage(response)
+      val data            = Await.result(Unmarshal(decodedResponse).to[String], 1.second)
+      data shouldBe "active: 1"
+    }
+
+    // unknown -> accept and skip encoding
+    Get("/metrics") ~> `Accept-Encoding`(HttpEncodings.`x-zip`) ~> route ~> check {
+      response should haveNoContentEncoding
       responseAs[String] shouldBe "active: 1"
     }
   }

prometheus/src/test/scala/fr/davit/pekko/http/metrics/prometheus/marshalling/PrometheusMarshallersSpec.scala

@@ -95,8 +95,7 @@ class PrometheusMarshallersSpec extends AnyFlatSpec with Matchers with Scalatest
   }
 
   it should "expose metrics as prometheus open-metrics format" in new Fixture {
-    val request = Get().addHeader(Accept(PrometheusMarshallers.OpenMetricsContentType.mediaType))
-    request ~> metrics(registry) ~> check {
+    Get() ~> Accept(PrometheusMarshallers.OpenMetricsContentType.mediaType) ~> metrics(registry) ~> check {
       response.entity.contentType shouldBe PrometheusMarshallers.OpenMetricsContentType
       val text    = responseAs[String]
       // println(text)
@@ -129,8 +128,7 @@ class PrometheusMarshallersSpec extends AnyFlatSpec with Matchers with Scalatest
   it should "expose metrics as prometheus protobuf format" in new Fixture {
     import io.prometheus.metrics.expositionformats.generated.com_google_protobuf_4_31_0.Metrics
 
-    val request = Get().addHeader(Accept(PrometheusMarshallers.ProtobufContentType.mediaType))
-    request ~> metrics(registry) ~> check {
+    Get() ~> Accept(PrometheusMarshallers.ProtobufContentType.mediaType) ~> metrics(registry) ~> check {
       response.entity.contentType shouldBe PrometheusMarshallers.ProtobufContentType
       val is = response.entity.dataBytes.runWith(StreamConverters.asInputStream())
       try {