`UNAVAILABLE: No grpc-status found` when using `akka-http` backend about akka-grpc

[johanandren]

I'd expect it is the client response whenever any server does not respond or can't be resolved (UNAVAILABLE - can't be reached). Since the server could not be reached the response does not contain a grpc-status header, logic for "recovering" the response is here

akka-grpc/runtime/src/main/scala/akka/grpc/internal/AkkaHttpClientUtils.scala

Line 275 in ddc302e

case None =>

[GreyPlane]

@johanandren during implements http transcoding for akka grpc, I was found the possible reason, and I think it's a bug or design flaw.

AkkaHttpClient always check if "grpc-status" exists and equal to "0".

akka-grpc/runtime/src/main/scala/akka/grpc/internal/AkkaHttpClientUtils.scala

Line 271 in 78210d8

case Some("0") =>

NettyClient seems doesn't check it.

akka-grpc/runtime/src/main/scala/akka/grpc/internal/UnaryCallAdapter.scala

Line 34 in 78210d8

if (status.isOk) {

Also I manually inspect the trailer headers, it doesn't contain grpc-status=0 for unknown reason in both backend, since according to the document, there should be explicit grpc-status for successful request.

[GreyPlane]

Since the server could not be reached the response does not contain a grpc-status header

In my case, there is no way that server cannot be reached since after I changed validation logic it just works fine.

I think I can provide reproduction if needed.

[johanandren]

If there is no grpc status in the response, it seems the error is correct?

[johanandren]

So definitely interesting to know if/when the Akka gRPC server emits such a response.

[GreyPlane]

uh, I think I've missed something, after experiments with client, it's works fine with AkkaHttpClient though I do find that NettyClient's onClose callback doesn't contains any trailer.

sry for misleading, I will continue to investigate when to put TrailerOK into response

[GreyPlane]

I found the reason why, since I was using generated grpcHandler directly(without network), HttpEntity is Strict instead of Chunked, so codes inside responseToSource doesn't retrieve trailer from attributes, so it's lost.

akka-grpc/runtime/src/main/scala/akka/grpc/internal/AkkaHttpClientUtils.scala

Line 222 in 78210d8

trailerPromise.success(immutable.Seq.empty)

I think it's OK to change it to retrieve trailer from attributes.

[jtjeferreira]

I implemented the suggested fix in #1906