StatusException metadata trailers not propagated to client

[Gregory-Berkman-Imprivata]

Metadata trailers are not being received when a request fails with a StatusException in zio-grpc 0.6.0 .

I have replicated this in the HelloWorldServer and HelloWorldClient

HelloWorldServer:

package zio_grpc.examples.helloworld

import io.grpc.Metadata.BinaryMarshaller
import io.grpc.{Metadata, Status, StatusException}
import scalapb.zio_grpc.ServerMain
import scalapb.zio_grpc.ServiceList
import zio._
import zio.Console._
import io.grpc.examples.helloworld.helloworld.ZioHelloworld.Greeter
import io.grpc.examples.helloworld.helloworld.{HelloReply, HelloRequest}

object GreeterImpl extends Greeter {
  def sayHello(
      request: HelloRequest
  ): ZIO[Any, StatusException, HelloReply] = {

    val metadataKey = Metadata.Key.of("foo-bin", new BinaryMarshaller[String] {
      override def toBytes(value: String): Array[Byte] = value.getBytes

      override def parseBytes(serialized: Array[Byte]): String = new String(serialized)
    })
    val metadata = new Metadata()
    metadata.put(metadataKey, "bar")

    (printLine(s"Got request: $request").orDie zipRight
      ZIO.fail(new StatusException(Status.INTERNAL, metadata)))
      .tapError(ex => printLine(ex.getTrailers.get(metadataKey)).orDie)
  }
}

object HelloWorldServer extends ServerMain {
  def services: ServiceList[Any] = ServiceList.add(GreeterImpl)
}

HelloWorldClient:

package zio_grpc.examples.helloworld

import io.grpc.examples.helloworld.helloworld.ZioHelloworld.GreeterClient
import io.grpc.examples.helloworld.helloworld.HelloRequest
import io.grpc.{ManagedChannelBuilder, Metadata}
import io.grpc.Metadata.BinaryMarshaller
import zio.Console._
import scalapb.zio_grpc.ZManagedChannel
import zio._

object HelloWorldClient extends zio.ZIOAppDefault {
  val clientLayer: Layer[Throwable, GreeterClient] =
    GreeterClient.live(
      ZManagedChannel(
        ManagedChannelBuilder.forAddress("localhost", 9000).usePlaintext()
      )
    )

  def myAppLogic = {
    val metadataKey = Metadata.Key.of("foo-bin", new BinaryMarshaller[String] {
      override def toBytes(value: String): Array[Byte] = value.getBytes

      override def parseBytes(serialized: Array[Byte]): String = new String(serialized)
    })

    for {
      r <- GreeterClient.sayHello(HelloRequest("World")).either
      _ <- r.fold(ex => printLine(s"${ex.getTrailers.get(metadataKey)}-${ex.getStatus}"), s => printLine(s.message))
    } yield ()
  }

  final def run =
    myAppLogic.provideLayer(clientLayer).exitCode
}

Server output:

Server is running on port 9000. Press Ctrl-C to stop.
Got request: HelloRequest(World,UnknownFieldSet(Map()))
bar

Expected Client output:

bar-Status{code=INTERNAL, description=null, cause=null}

Actual Client output:

null-Status{code=INTERNAL, description=null, cause=null}

As you can see the client receives null within the exception trailer metadata.

[thesamet]

Thanks for reporting! Will you be able to work on a PR to fix this?

On Tue, Aug 22, 2023 at 10:32 AM Gregory-Berkman-Imprivata < @.***> wrote:

Metadata trailers are not being received when a request fails with a StatusException in zio-grpc 0.6.0 .

I have replicated this in the HelloWorldServer and HelloWorldClient

HelloWorldServer:

package zio_grpc.examples.helloworld

import io.grpc.Metadata.BinaryMarshaller import io.grpc.{Metadata, Status, StatusException} import scalapb.zio_grpc.ServerMain import scalapb.ziogrpc.ServiceList import zio. import zio.Console._ import io.grpc.examples.helloworld.helloworld.ZioHelloworld.Greeter import io.grpc.examples.helloworld.helloworld.{HelloReply, HelloRequest}

object GreeterImpl extends Greeter { def sayHello( request: HelloRequest ): ZIO[Any, StatusException, HelloReply] = {

val metadataKey = Metadata.Key.of("foo-bin", new BinaryMarshaller[String] {
  override def toBytes(value: String): Array[Byte] = value.getBytes

  override def parseBytes(serialized: Array[Byte]): String = new String(serialized)
})
val metadata = new Metadata()
metadata.put(metadataKey, "bar")

(printLine(s"Got request: $request").orDie zipRight
  ZIO.fail(new StatusException(Status.INTERNAL, metadata)))
  .tapError(ex => printLine(ex.getTrailers.get(metadataKey)).orDie)

} }

object HelloWorldServer extends ServerMain { def services: ServiceList[Any] = ServiceList.add(GreeterImpl) }

HelloWorldClient:

package zio_grpc.examples.helloworld

import io.grpc.examples.helloworld.helloworld.ZioHelloworld.GreeterClient import io.grpc.examples.helloworld.helloworld.HelloRequest import io.grpc.{ManagedChannelBuilder, Metadata} import io.grpc.Metadata.BinaryMarshaller import zio.Console._ import scalapb.ziogrpc.ZManagedChannel import zio.

object HelloWorldClient extends zio.ZIOAppDefault { val clientLayer: Layer[Throwable, GreeterClient] = GreeterClient.live( ZManagedChannel( ManagedChannelBuilder.forAddress("localhost", 9000).usePlaintext() ) )

def myAppLogic = { val metadataKey = Metadata.Key.of("foo-bin", new BinaryMarshaller[String] { override def toBytes(value: String): Array[Byte] = value.getBytes

  override def parseBytes(serialized: Array[Byte]): String = new String(serialized)
})

for {
  r <- GreeterClient.sayHello(HelloRequest("World")).either
  _ <- r.fold(ex => printLine(s"${ex.getTrailers.get(metadataKey)}-${ex.getStatus}"), s => printLine(s.message))
} yield ()

}

final def run = myAppLogic.provideLayer(clientLayer).exitCode }

Server output:

Server is running on port 9000. Press Ctrl-C to stop. Got request: HelloRequest(World,UnknownFieldSet(Map())) bar

Expected Client output:

bar-Status{code=INTERNAL, description=null, cause=null}

Actual Client output:

null-Status{code=INTERNAL, description=null, cause=null}

As you can see the client receives null within the exception trailer metadata.

— Reply to this email directly, view it on GitHub https://github.com/scalapb/zio-grpc/issues/547, or unsubscribe https://github.com/notifications/unsubscribe-auth/AACLBLPQ2UOFNZ24IYOPNATXWTULHANCNFSM6AAAAAA32IK3OU . You are receiving this because you are subscribed to this thread.Message ID: @.***>

-- -Nadav

[Gregory-Berkman-Imprivata]

i can try. I havent contributed yet and am not too familiar with the code. I really need this feature though.

[thesamet]

Thanks - the first step would be adding a failing test under the e2e directory, probably under https://github.com/scalapb/zio-grpc/blob/master/e2e/src/test/scalajvm/scalapb/zio_grpc/TestServiceSpec.scala

• then digging in the "core" directory to see what the problem/fix might be. The e2e tests can be easily run from sbt, type projects to see the list of projects, there are suffixes for different Scala versions.

On Tue, Aug 22, 2023 at 10:45 AM Gregory-Berkman-Imprivata < @.***> wrote:

i can try. I havent contributed yet and am not too familiar with the code. I really need this feature though.

— Reply to this email directly, view it on GitHub https://github.com/scalapb/zio-grpc/issues/547#issuecomment-1688644912, or unsubscribe https://github.com/notifications/unsubscribe-auth/AACLBLOEI47ZYYFFCYKYGE3XWTVZ7ANCNFSM6AAAAAA32IK3OU . You are receiving this because you commented.Message ID: @.***>

-- -Nadav

[Gregory-Berkman-Imprivata]

I think I may have found a way to add the trailers to the metadata. I went to put up a PR to discuss but I do not have access permissions to push a branch.

[thesamet]

You can send a PR by pushing a branch to your personal fork of this project.

[thesamet]

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request-from-a-fork

[Gregory-Berkman-Imprivata]

I figured out how to do this in my application so I am no longer blocked.

class PropagatingMetadataTrailersTransformer extends GTransform[RequestContext, StatusException, RequestContext, StatusException] {

    def effect[A](
      io: RequestContext => ZIO[Any, StatusException, A]
    ): (RequestContext => ZIO[Any, StatusException, A]) = { context => 
        io(context).tapError(ex => context.responseMetadata.wrap(_.merge(ex.getTrailers)))
    }

    ...
} 

I attempted to implement a similar solution in the PR but tests were failing. Any reason a solution like this could cause issues?

[thesamet]

Not seeing an obvious issue with the workaround.