Support JSON Transcoding for gRPC services -- allows services to be called via plain HTTP

[GavinRay97]

Description

It would be really useful if Quarkus' gRPC implementation allowed configuring JSON Transcoding:

• https://cloud.google.com/endpoints/docs/grpc/transcoding
• https://devblogs.microsoft.com/dotnet/announcing-grpc-json-transcoding-for-dotnet/

(Maybe it already does this and I just missed the docs/tests?)

syntax = "proto3";
import "google/api/annotations.proto";
package greet;

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {
    option (google.api.http) = {
      get: "/v1/greeter/{name}"
    };
  }
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

Implementation ideas

No response

[quarkus-bot]

/cc @cescoffier, @michalszynkiewicz

[michalszynkiewicz]

Quarkus does not support it at the moment but it is a nice idea. I have no idea where we'll have time to implement it though, at this point.

[GavinRay97]

Trying to think about how this could potentially work (maybe I could take a stab at it)

1. Find a Java .proto parser
   • https://github.com/square/protoparser
2. Write a codegen program that analyzes .proto services and creates:
   • JSON-to-Protobuf serialization code
     • https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/advanced/JsonMarshaller.java
   • RESTEasy Reactive route handler that listens on IE /grpc/** and does internal lookup/delegation
3. Make this into a Quarkus plugin, or Maven/Gradle

Does this sound reasonable? Are there hangups that someone might run into with this?

[cescoffier]

Yes, it looks like a good plan. I would not register endpoints in RestEasy reactive but work at the 'router' level directly (so you do not need RestEasy reactive, just vertx htttp which is the base of everything Http related).

Also we need to think about streams. Did you think about them?

[hardikp-fens]

I wanted to utilize this feature in my quarkus project, so are there any updates regarding this?

/cc @cescoffier, @michalszynkiewicz

[schonbachler]

This would be a very useful feature. gRPC-web transcoding would be a related feature. As of now - a possible solution is to use a reverse-proxy (like envoy) in front, that does the transcoding.

[cescoffier]

Vert.x is coming with an implementation of the gRPC Web "proxy" which would be built in in the gRPC server.

CC @tsegismont

[cescoffier]

Vert.x 5 is coming with gRPC Web support - We will integrate gRPC Web at that point (2025).

[schonbachler]

@cescoffier Great news. Please keep in mind that grpc web and grpc JSON transcoding are two different things.

[cescoffier]

@schonbachler I know, but at the moment, our priority is gRPC Web. Contributions are more than welcome for gRPC JSON.