add pekko grpc support

build.sbt

@@ -188,6 +188,7 @@ lazy val rawAllAggregates = core.projectRefs ++
   protobuf.projectRefs ++
   pbDirectProtobuf.projectRefs ++
   grpcExamples.projectRefs ++
+  pekkoGrpcExamples.projectRefs ++
   apispecDocs.projectRefs ++
   openapiDocs.projectRefs ++
   asyncapiDocs.projectRefs ++
@@ -200,6 +201,7 @@ lazy val rawAllAggregates = core.projectRefs ++
   akkaHttpServer.projectRefs ++
   akkaGrpcServer.projectRefs ++
   pekkoHttpServer.projectRefs ++
+  pekkoGrpcServer.projectRefs ++
   armeriaServer.projectRefs ++
   armeriaServerCats.projectRefs ++
   armeriaServerZio.projectRefs ++
@@ -987,6 +989,23 @@ lazy val grpcExamples: ProjectMatrix = (projectMatrix in file("grpc/examples"))
     akkaGrpcServer
   )
 
+lazy val pekkoGrpcExamples: ProjectMatrix = (projectMatrix in file("grpc/pekko-examples"))
+  .settings(commonSettings)
+  .settings(
+    name := "tapir-pekko-grpc-examples",
+    libraryDependencies ++= Seq(
+      "org.apache.pekko" %% "pekko-discovery" % "1.0.1"
+    ),
+    fork := true
+  )
+  .enablePlugins(PekkoGrpcPlugin)
+  .jvmPlatform(scalaVersions = scala2Versions)
+  .dependsOn(
+    protobuf,
+    pbDirectProtobuf,
+    pekkoGrpcServer
+  )
+
 // metrics
 
 lazy val prometheusMetrics: ProjectMatrix = (projectMatrix in file("metrics/prometheus-metrics"))
@@ -1216,6 +1235,17 @@ lazy val akkaGrpcServer: ProjectMatrix = (projectMatrix in file("server/akka-grp
   .jvmPlatform(scalaVersions = scala2Versions)
   .dependsOn(serverCore, akkaHttpServer)
 
+lazy val pekkoGrpcServer: ProjectMatrix = (projectMatrix in file("server/pekko-grpc-server"))
+  .settings(commonJvmSettings)
+  .settings(
+    name := "tapir-pekko-grpc-server",
+    libraryDependencies ++= Seq(
+      "org.apache.pekko" %% "pekko-grpc-runtime" % "1.0.0"
+    )
+  )
+  .jvmPlatform(scalaVersions = scala2And3Versions)
+  .dependsOn(serverCore, pekkoHttpServer)
+
 lazy val armeriaServer: ProjectMatrix = (projectMatrix in file("server/armeria-server"))
   .settings(commonJvmSettings)
   .settings(

doc/grpc.md

@@ -13,6 +13,8 @@ from these endpoints' definitions.
   necessary to add this module for generating proto files with the `protobuf` module.
 * `akkaGrpcServer` - a module that provides `AkkaGrpcServerInterpreter` implementation. It should be used to serve tapir
   grpc endpoints.
+* `pekkoGrpcServer` - a module that provides `PekkoGrpcServerInterpreter` implementation. It can be used as an
+  alternative to `akkaGrpcServer`.
 * `grpcExamples` - contains example use cases
 
 ## Defining endpoints

grpc/pekko-examples/src/main/protobuf/simple_books_example.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "sttp.tapir.grpc.examples.grpc_simple_books_example.gen";
+
+service Library {
+  rpc AddBook (AddBookMsg) returns (SimpleBook) {}
+}
+
+message SimpleBook {
+  int32 id = 1;
+  string title = 2;
+  string description = 3;
+}
+
+message AddBookMsg {
+  string title = 1;
+  string description = 2;
+}

grpc/pekko-examples/src/main/scala/sttp/tapir/grpc/examples/PekkoGrpcSimpleBooksExample.scala

@@ -0,0 +1,98 @@
+package sttp.tapir.grpc.examples
+
+import org.apache.pekko.actor.ActorSystem
+import org.apache.pekko.grpc.GrpcClientSettings
+import org.apache.pekko.http.scaladsl.Http
+import cats.implicits._
+import com.typesafe.config.ConfigFactory
+import com.typesafe.scalalogging.StrictLogging
+import sttp.tapir._
+import sttp.tapir.grpc.protobuf._
+import sttp.tapir.grpc.protobuf.pbdirect._
+import sttp.tapir.server.ServerEndpoint
+import sttp.tapir.server.pekkogrpc.PekkoGrpcServerInterpreter
+import sttp.tapir.generic.auto._
+import sttp.tapir.grpc.examples.grpc_simple_books_example.gen.{
+  Library => GenLibrary,
+  LibraryClient => GenLibraryClient,
+  AddBookMsg => GenAddBookMsg
+}
+
+import java.util.concurrent.atomic.AtomicLong
+import scala.concurrent.{Await, ExecutionContext, Future}
+
+case class SimpleBook(id: Long, title: String, description: String)
+case class AddBookMsg(title: String, description: String)
+
+/** Descriptions of endpoints used in the example.
+  */
+object Endpoints {
+  val addBook = endpoint
+    .in("Library" / "AddBook")
+    .in(grpcBody[AddBookMsg])
+    .out(grpcBody[SimpleBook])
+
+  val endpoints = List(addBook)
+}
+
+object SimpleBooksExampleServer extends StrictLogging {
+
+  import Endpoints._
+
+  private val counter = new AtomicLong(0)
+
+  def booksServerEndpoints: List[ServerEndpoint[Any, Future]] =
+    List(
+      addBook.serverLogic { book =>
+        logger.info(s"Adding a new book [$book]")
+        Future.successful(SimpleBook(counter.getAndIncrement(), book.title, book.description).asRight[Unit])
+      }
+    )
+
+  def main(args: Array[String]): Unit = {
+    val conf = ConfigFactory
+      .parseString("pekko.http.server.preview.enable-http2 = on")
+      .withFallback(ConfigFactory.defaultApplication())
+    val system = ActorSystem("HelloWorld", conf)
+
+    new ExampleGrpcServer(system).run()
+  }
+}
+
+class ExampleGrpcServer(system: ActorSystem) extends StrictLogging {
+  def run(): Future[Http.ServerBinding] = {
+    // Pekko boot up code
+    implicit val sys: ActorSystem = system
+    implicit val ec: ExecutionContext = sys.dispatcher
+
+    val route = PekkoGrpcServerInterpreter().toRoute(SimpleBooksExampleServer.booksServerEndpoints)
+
+    val binding = Http().newServerAt("127.0.0.1", 8080).bind(route)
+
+    // report successful binding
+    binding.foreach { binding => logger.info(s"gRPC server bound to: ${binding.localAddress}") }
+
+    binding
+  }
+}
+
+object SimpleBookExampleProtoGenerator extends App {
+  ProtoSchemaGenerator.renderToFile(
+    path = "grpc/examples/src/main/protobuf/simple_books_example.proto",
+    packageName = "sttp.tapir.grpc.examples.grpc_simple_books_example.gen",
+    endpoints = Endpoints.endpoints
+  )
+}
+
+object SimpleBookExampleClient extends App with StrictLogging {
+
+  import scala.concurrent.duration._
+
+  implicit val sys = ActorSystem("HelloWorldClient")
+  implicit val ec = sys.dispatcher
+
+  val client = GenLibraryClient(GrpcClientSettings.connectToServiceAt("localhost", 8080).withTls(false))
+  val result = Await.result(client.addBook(GenAddBookMsg("TEST_BOOK", "TEST")), 10.second)
+
+  logger.info(s"Result: [$result]")
+}

project/plugins.sbt

@@ -18,5 +18,8 @@ addSbtPlugin("io.gatling" % "gatling-sbt" % "4.5.0")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.11.0")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.4.15")
 addSbtPlugin("com.lightbend.akka.grpc" % "sbt-akka-grpc" % "2.1.4")
+addSbtPlugin("org.apache.pekko" % "pekko-grpc-sbt-plugin" % "1.0.0")
+// needed to override the Android flavor of Guava coming from pekko-grpc-sbt-plugin, which causes failures in Scala.JS builds
+dependencyOverrides += "com.google.guava" % "guava" % "32.1.2-jre"
 
 addDependencyTreePlugin

server/pekko-grpc-server/src/main/scala/sttp/tapir/server/pekkogrpc/PekkoGrpcRequestBody.scala

@@ -0,0 +1,52 @@
+package sttp.tapir.server.pekkogrpc
+
+import org.apache.pekko.grpc.internal.{GrpcProtocolNative, Identity, SingleParameterSink}
+import org.apache.pekko.http.scaladsl.model.HttpEntity
+import org.apache.pekko.http.scaladsl.server.RequestContext
+import org.apache.pekko.stream.Materializer
+import org.apache.pekko.util.ByteString
+import sttp.capabilities.pekko.PekkoStreams
+import sttp.tapir.{InputStreamRange, RawBodyType}
+import sttp.tapir.model.ServerRequest
+import sttp.tapir.server.pekkohttp.PekkoHttpServerOptions
+import sttp.tapir.server.interpreter.{RawValue, RequestBody}
+
+import java.io.ByteArrayInputStream
+import scala.concurrent.{ExecutionContext, Future}
+import scala.util.Try
+
+private[pekkogrpc] class PekkoGrpcRequestBody(serverOptions: PekkoHttpServerOptions)(implicit
+    mat: Materializer,
+    ec: ExecutionContext
+) extends RequestBody[Future, PekkoStreams] {
+  private val grpcProtocol = GrpcProtocolNative.newReader(Identity)
+
+  override val streams: PekkoStreams = PekkoStreams
+  override def toRaw[R](request: ServerRequest, bodyType: RawBodyType[R]): Future[RawValue[R]] =
+    toRawFromEntity(request, akkaRequestEntity(request), bodyType)
+
+  override def toStream(request: ServerRequest): streams.BinaryStream = ???
+
+  private def akkaRequestEntity(request: ServerRequest) = request.underlying.asInstanceOf[RequestContext].request.entity
+
+  private def toRawFromEntity[R](request: ServerRequest, body: HttpEntity, bodyType: RawBodyType[R]): Future[RawValue[R]] = {
+    // Copy-paste from akka.grpc.scaladsl.GrpcMarshalling#unmarshal
+    body match {
+      case HttpEntity.Strict(_, data) => Future.fromTry(Try(toExpectedBodyType(data, bodyType)))
+      case _ => body.dataBytes.via(grpcProtocol.dataFrameDecoder).map(toExpectedBodyType(_, bodyType)).runWith(SingleParameterSink())
+    }
+  }
+
+  private def toExpectedBodyType[R](byteString: ByteString, bodyType: RawBodyType[R]): RawValue[R] = {
+    bodyType match {
+      case RawBodyType.ByteArrayBody        => RawValue(byteString.toArray)
+      case RawBodyType.ByteBufferBody       => RawValue(byteString.asByteBuffer)
+      case RawBodyType.InputStreamBody      => RawValue(new ByteArrayInputStream(byteString.toArray))
+      case RawBodyType.InputStreamRangeBody => RawValue(InputStreamRange(() => new ByteArrayInputStream(byteString.toArray)))
+      case RawBodyType.FileBody             => ???
+      case m: RawBodyType.MultipartBody     => ???
+      case _                                => ???
+    }
+  }
+
+}

server/pekko-grpc-server/src/main/scala/sttp/tapir/server/pekkogrpc/PekkoGrpcServerInterpreter.scala

@@ -0,0 +1,21 @@
+package sttp.tapir.server.pekkogrpc
+
+import org.apache.pekko.http.scaladsl.server.Route
+import sttp.capabilities.WebSockets
+import sttp.capabilities.pekko.PekkoStreams
+import sttp.tapir.server.ServerEndpoint
+import sttp.tapir.server.pekkohttp.PekkoHttpServerInterpreter
+
+import scala.concurrent.{ExecutionContext, Future}
+
+trait PekkoGrpcServerInterpreter extends PekkoHttpServerInterpreter {
+  override def toRoute(ses: List[ServerEndpoint[PekkoStreams with WebSockets, Future]]): Route =
+    toRoute(new PekkoGrpcRequestBody(pekkoHttpServerOptions)(_, _), new PekkoGrpcToResponseBody()(_, _))(ses)
+
+}
+
+object PekkoGrpcServerInterpreter {
+  def apply()(implicit _ec: ExecutionContext): PekkoGrpcServerInterpreter = new PekkoGrpcServerInterpreter {
+    override implicit def executionContext: ExecutionContext = _ec
+  }
+}

server/pekko-grpc-server/src/main/scala/sttp/tapir/server/pekkogrpc/PekkoGrpcToResponseBody.scala

@@ -0,0 +1,88 @@
+package sttp.tapir.server.pekkogrpc
+
+import org.apache.pekko.grpc.internal.AbstractGrpcProtocol
+import org.apache.pekko.http.scaladsl.model._
+import org.apache.pekko.stream.Materializer
+import org.apache.pekko.util.ByteString
+import sttp.capabilities.pekko.PekkoStreams
+import sttp.model.HasHeaders
+import sttp.tapir.internal.charset
+import sttp.tapir.server.pekkohttp.PekkoResponseBody
+import sttp.tapir.server.interpreter.ToResponseBody
+import sttp.tapir.{CodecFormat, RawBodyType, WebSocketBodyOutput}
+
+import java.nio.charset.{Charset, StandardCharsets}
+import scala.concurrent.ExecutionContext
+
+private[pekkogrpc] class PekkoGrpcToResponseBody(implicit m: Materializer, ec: ExecutionContext)
+    extends ToResponseBody[PekkoResponseBody, PekkoStreams] {
+  override val streams: PekkoStreams = PekkoStreams
+
+  override def fromRawValue[R](v: R, headers: HasHeaders, format: CodecFormat, bodyType: RawBodyType[R]): PekkoResponseBody =
+    Right(
+      overrideContentTypeIfDefined(
+        rawValueToResponseEntity(bodyType, formatToContentType(format, charset(bodyType)), headers.contentLength, v),
+        headers
+      )
+    )
+
+  override def fromStreamValue(
+      v: streams.BinaryStream,
+      headers: HasHeaders,
+      format: CodecFormat,
+      charset: Option[Charset]
+  ): PekkoResponseBody = ???
+
+  override def fromWebSocketPipe[REQ, RESP](
+      pipe: streams.Pipe[REQ, RESP],
+      o: WebSocketBodyOutput[streams.Pipe[REQ, RESP], REQ, RESP, _, PekkoStreams]
+  ): PekkoResponseBody = ???
+
+  private def rawValueToResponseEntity[CF <: CodecFormat, R](
+      bodyType: RawBodyType[R],
+      ct: ContentType,
+      contentLength: Option[Long],
+      r: R
+  ): ResponseEntity = {
+    bodyType match {
+      case RawBodyType.StringBody(charset)  => ???
+      case RawBodyType.ByteArrayBody        => HttpEntity(ct, encodeDataToFrameBytes(ByteString(r)))
+      case RawBodyType.ByteBufferBody       => HttpEntity(ct, encodeDataToFrameBytes(ByteString(r)))
+      case RawBodyType.InputStreamBody      => ???
+      case RawBodyType.InputStreamRangeBody => ???
+      case RawBodyType.FileBody             => ???
+      case m: RawBodyType.MultipartBody     => ???
+    }
+  }
+
+  private def formatToContentType(format: CodecFormat, charset: Option[Charset]): ContentType = {
+    format match {
+      case CodecFormat.Json()        => ContentTypes.`application/json`
+      case CodecFormat.TextPlain()   => MediaTypes.`text/plain`.withCharset(charsetToHttpCharset(charset.getOrElse(StandardCharsets.UTF_8)))
+      case CodecFormat.TextHtml()    => MediaTypes.`text/html`.withCharset(charsetToHttpCharset(charset.getOrElse(StandardCharsets.UTF_8)))
+      case CodecFormat.OctetStream() => MediaTypes.`application/octet-stream`
+      case CodecFormat.Zip()         => MediaTypes.`application/zip`
+      case CodecFormat.XWwwFormUrlencoded() => MediaTypes.`application/x-www-form-urlencoded`
+      case CodecFormat.MultipartFormData()  => MediaTypes.`multipart/form-data`
+      case f =>
+        val mt = if (f.mediaType.isText) charset.fold(f.mediaType)(f.mediaType.charset(_)) else f.mediaType
+        parseContentType(mt.toString())
+    }
+  }
+
+  private def parseContentType(ct: String): ContentType =
+    ContentType.parse(ct).getOrElse(throw new IllegalArgumentException(s"Cannot parse content type: $ct"))
+
+  private def charsetToHttpCharset(charset: Charset): HttpCharset = HttpCharset.custom(charset.name())
+
+  private def overrideContentTypeIfDefined[RE <: ResponseEntity](re: RE, headers: HasHeaders): RE = {
+    headers.contentType match {
+      case Some(ct) => re.withContentType(parseContentType(ct)).asInstanceOf[RE]
+      case None     => re
+    }
+  }
+
+  // TODO support for compressed body
+  private def encodeDataToFrameBytes(data: ByteString): ByteString =
+    AbstractGrpcProtocol.encodeFrameData(data, isCompressed = false, isTrailer = false)
+}